By any measure, AIDS is a frightening disease. It is physically devastating, incurable, and lethal. And it is spreading at a menacing pace. Fear and misconceptions about AIDS, however, have spread faster than the disease itself.
Federal health officials stress that the AIDS virus has spread almost exclusively by three routes: by sexual intercourse, through blood contact (contamination with or transfusion of infected blood or blood products), and from an infected pregnant woman to her fetus or newborn. The only other known instances in which the virus was transmitted, say officials, involved artificial insemination or organ transplants from infected donors.
But many people remain unconvinced. They fear that casual personal contact with an AIDS victim—a handshake, a sneeze, a drink from the same glass—might lead to infection. A child with AIDS attempting to attend school can throw a community into a frenzy. An AIDS patient returning to work may find coworkers deserting the job in protest.
In short, anxiety about AIDS has itself become epidemic. Part of the problem is that AIDS is a new disease—mysterious in its origin and initially baffling in its symptoms and cause. But the impression that scientists are groping amid a welter of unresolved questions is misleading. A vast amount of critical knowledge has already been gained about AIDS, and more is being learned all the time.
The epidemic first surfaced in the late 1970s, when rare cancers and uncommon infections began appearing in a number of gay (homosexual) men. Those illnesses were linked with a severe deficiency in the body's immune-defense system—a disorder initially called GRID, for Gay-Related Immune Deficiency. As late as mid-1981, gay men were still the only known victims in the United States, creating the impression that AIDS arose from something exclusive to that group.
By 1982, when the name became AIDS, for "acquired immune deficiency syndrome," the first currents of fear jolted the health-care community. The number of AIDS cases was rising geometrically, and the disease had appeared in two more groups—intravenous drug users and hemophiliacs. Not only did the pattern imply an infectious agent, but the disease was now affecting three of the principal groups vulnerable to hepatitis B infection—a viral illness that's also an occupational hazard among health workers.
AIDS would subsequently prove to be much less contagious than hepatitis B, partly because the number of hepatitis B virus particles in blood is up to a billion times greater than the number of AIDS virus particles. But no one knew that in 1982. Nor was it known that the AIDS virus doesn't penetrate intact skin or the linings of the respiratory and digestive tracts—and thus could not be transmitted by such things as a kiss on the lips, a cough, or food prepared by a person with AIDS.
With the number of cases doubling every six months, medical personnel on the front line became increasingly fearful for their own safety. That fear soon became evident to the public at large, helping to confirm impressions that a virulent plague was loose in the land. As public fear of the threat grew, scientific understanding of the disease advanced rapidly.
By mid-1984, three independent research teams in the United States and France had conclusively identified the virus that causes AIDS. Discovery of the virus—now designated "human immunodeficiency virus," or HIV—immediately opened new avenues of research into every aspect of the disease. Investigators have already deciphered the genetic code of the virus in search of ways to attack it. Others probing for clues to therapy have explored its crippling effect on the immune system.
For epidemiologists, who investigate the incidence, transmission, and patterns of disease, identification of the virus was the indispensable handle for a powerful new tool. It meant that a test could now be developed to detect individual exposure to the virus, information vital for deeper insight into the epidemic and its spread.
Federal health officials stress that the AIDS virus has spread almost exclusively by three routes: by sexual intercourse, through blood contact (contamination with or transfusion of infected blood or blood products), and from an infected pregnant woman to her fetus or newborn. The only other known instances in which the virus was transmitted, say officials, involved artificial insemination or organ transplants from infected donors.
But many people remain unconvinced. They fear that casual personal contact with an AIDS victim—a handshake, a sneeze, a drink from the same glass—might lead to infection. A child with AIDS attempting to attend school can throw a community into a frenzy. An AIDS patient returning to work may find coworkers deserting the job in protest.
In short, anxiety about AIDS has itself become epidemic. Part of the problem is that AIDS is a new disease—mysterious in its origin and initially baffling in its symptoms and cause. But the impression that scientists are groping amid a welter of unresolved questions is misleading. A vast amount of critical knowledge has already been gained about AIDS, and more is being learned all the time.
The epidemic first surfaced in the late 1970s, when rare cancers and uncommon infections began appearing in a number of gay (homosexual) men. Those illnesses were linked with a severe deficiency in the body's immune-defense system—a disorder initially called GRID, for Gay-Related Immune Deficiency. As late as mid-1981, gay men were still the only known victims in the United States, creating the impression that AIDS arose from something exclusive to that group.
By 1982, when the name became AIDS, for "acquired immune deficiency syndrome," the first currents of fear jolted the health-care community. The number of AIDS cases was rising geometrically, and the disease had appeared in two more groups—intravenous drug users and hemophiliacs. Not only did the pattern imply an infectious agent, but the disease was now affecting three of the principal groups vulnerable to hepatitis B infection—a viral illness that's also an occupational hazard among health workers.
AIDS would subsequently prove to be much less contagious than hepatitis B, partly because the number of hepatitis B virus particles in blood is up to a billion times greater than the number of AIDS virus particles. But no one knew that in 1982. Nor was it known that the AIDS virus doesn't penetrate intact skin or the linings of the respiratory and digestive tracts—and thus could not be transmitted by such things as a kiss on the lips, a cough, or food prepared by a person with AIDS.
With the number of cases doubling every six months, medical personnel on the front line became increasingly fearful for their own safety. That fear soon became evident to the public at large, helping to confirm impressions that a virulent plague was loose in the land. As public fear of the threat grew, scientific understanding of the disease advanced rapidly.
By mid-1984, three independent research teams in the United States and France had conclusively identified the virus that causes AIDS. Discovery of the virus—now designated "human immunodeficiency virus," or HIV—immediately opened new avenues of research into every aspect of the disease. Investigators have already deciphered the genetic code of the virus in search of ways to attack it. Others probing for clues to therapy have explored its crippling effect on the immune system.
For epidemiologists, who investigate the incidence, transmission, and patterns of disease, identification of the virus was the indispensable handle for a powerful new tool. It meant that a test could now be developed to detect individual exposure to the virus, information vital for deeper insight into the epidemic and its spread.
Elisa: Testing for Exposure to Aids
By 1985, a simple, inexpensive blood test for detecting exposure to the AIDS virus had been developed and approved for use. Called ELISA (for enzyme-linked immunosorbent assay), the test detects antibodies produced by white blood cells in response to the presence of the virus. Developed primarily to screen potential blood donors, ELISA has also served as a versatile research tool, greatly facilitating analysis of the epidemic's path.
Before ELISA, it was difficult to trace the spread of the virus. There was no practical way to detect it in people without symptoms, who represent the largest number of those infected. By mid-1988, about 65,000 cases of AIDS had been reported to the U.S. Centers for Disease Control (CDC). An estimated 325,000 people had AIDS-related complex (ARC), a term used to describe a condition that includes (in addition to laboratory evidence of immunodeficiency) swollen glands, recurrent fever, weight loss, or a combination of those symptoms. When persons with ARC develop any one of a number of opportunistic infections (or Kaposi's sarcoma), they are considered to have developed AIDS.
An estimated 1.6 million to 3.2 million additional people may be infected with the virus but have no symptoms of illness. Although their blood reveals antibodies to the virus—as determined by two consistently positive ELISA tests and a more sophisticated (and costly) confirming test called Western blot analysis—they may have no other laboratory or clinical signs of disease. Most public-health officials estimate that 30 to 50 percent of those people will ultimately develop full-blown AIDS.
With a practical means of detection in hand, researchers began probing areas previously obscure. For example, how fast was the virus spreading to the general population—or among intravenous-drug users, or gay men? Was it infecting family members who had no sexual contact with a victim in the home? Were some sexual practices riskier than others? Since 1985, a wealth of new information has become available to address those questions and others.
Some of the findings are uncompromisingly bleak. Among high-risk groups, the AIDS virus is cutting a widening swath of infection, particularly in areas that have already borne the brunt of the epidemic, such as metropolitan New York and San Francisco. The infection is also spreading among young adults in inner-city minority groups, especially black and Hispanic intravenous-drug users and their sexual partners. One analysis of blood tests administered to some 300,000 military recruits found the rate of infection in blacks to be four times that in whites.
Federal health officials have predicted that the cumulative total of AIDS cases could reach 270,000 by 1991, with 179,000 deaths. Most of those will be people who are already infected with the virus, the officials said.
The grim projections of unfolding tragedy have overshadowed all other emerging information about the epidemic. But there has been another side to the news. An increasing number of epidemiological studies now point to an unmistakable conclusion: The reassurances from health officials about casual contact with AIDS patients are well founded. As CDC director James O. Mason, M.D., put it, "This is a very difficult disease to catch."
Transmission appears to require not only direct insertion of the virus into the bloodstream but also a substantial dose of the virus—much more than could be transmitted by casual contact. Indeed, a consistent pattern in people who become infected is frequent or severe exposure to the virus.
Even in sexual intercourse—the primary route of infection—the virus does not appear to spread easily. Like most sexually transmitted diseases, AIDS is strongly associated with a highly active sex life and multiple partners.
Homosexual Transmission
Among gay and bisexual men, the disease first appeared in those with extremely large numbers of sexual partners—a lifetime average of over 1000 partners, according to one early epidemiologic study. It's not known whether multiple sexual contacts raise the risk simply by raising the odds that a person will encounter the AIDS virus once, or by some process in which the body's defenses are worn down (perhaps through exposure to other sexually transmitted diseases), or both. All that's known for sure is that having a large number of sexual partners raises the risk.
Now that the virus is more prevalent—and the odds of catching it (among people at risk) are higher—the average number of sexual partners reported by people who contract the disease would be far less than 1000. No precise numbers, however, are available.
A key factor in the rapid spread of the virus among gay and bisexual men is the practice of anal intercourse, probably because the surface membranes and blood vessels of the anal canal are vulnerable to small fissures or tears during intercourse. Such tears may allow virus carried in semen to gain entry into the bloodstream of the receiving partner. The risk of viral transmission is especially high for the partner accepting penetration (receptive anal intercourse). In one six-month study examining transmission of the virus in gay men, a University of Pittsburgh research team found receptive anal intercourse to be the major risk factor in infection. At the outset, none of the men showed any evidence of AIDS virus in their blood. After six months, however, antibodies to the virus were found in a number of the subjects, especially among men who had had two or more sexual partners. In that group, men engaging in receptive anal intercourse had 16 times the infection rate as those having no anal intercourse.
As yet, there's no scientific evidence that sexual practices other than anal-related sex lead to AIDS-virus transmission in gay men. However, only a few large studies have compared the effects of different sexual practices.
One such study was conducted by University of California researchers over a two-year period for the San Francisco Men's Health Study. The California investigators examined infection rates among some 800 gay or bisexual men with different sexual histories. No difference in infection rates was found between those who engaged solely in oral-genital sex and those who had no sexual partners at all.
The California researchers concluded that the risk of AIDS-virus transmission by oral-genital contact was minimal. But they cautioned—as did the Pittsburgh group—that their findings did not prove that sexual activity other than anal intercourse posed no risk among gay men. They pointed out that their results were based on a relatively small number of observations and could not completely exclude the possibility of transmission by oral-genital sex.
Indeed, caution has been the watchword among public-health officials offering preventive advice. Since more than 90 percent of AIDS cases have occurred in gay or bisexual men and intravenous-drug users, the message to those high-risk groups has stressed avoiding any possible risk. One drawback of that approach, however, is that it makes AIDS appear easier to catch than it actually is. Some public-health workers, for example, warn against deep kissing involving exchange of saliva. But there's no evidence that the virus is transmitted that way.
Heterosexual Transmission
In contrast to oral sex or deep kissing, vaginal intercourse is clearly an important route of infection. The AIDS virus can be spread by either a man or a woman during intercourse.
On a relative scale, vaginal intercourse appears to be less effective in spreading the virus than anal intercourse, and less contagious from female to male than the reverse. As yet, the risk of transmission in a single act of vaginal intercourse is unknown. But current evidence suggests that frequent or long-term sexual exposure with an infected partner or partners is an important factor in transmission.
As of mid-1988, about 4 percent of newly diagnosed AIDS cases in the U.S. can be traced to heterosexual transmission. A large number of the victims are spouses or long-term sexual partners of AIDS patients or other high-risk individuals, particularly intravenous-drug users. Another large segment includes immigrants from Haiti and central Africa, where the virus spreads mainly by heterosexual intercourse.
Some confusion initially surrounded the status of Haitians, who were once listed as a separate risk group for AIDS. Epidemiologists have since found that the infection rate is not high among Haitians who are longterm U.S. residents. It's high, though, among recent immigrants with a history of venereal disease or sexual contact with prostitutes. In both Haiti and central Africa, infected prostitutes are an important factor in the spread of the virus among heterosexuals.
Reports from central Africa also show that AIDS is concentrated among urban people who are very sexually active. The average AIDS patient had more than 30 sex partners a year, including frequent contacts with prostitutes.
Overall, heterosexual spread of the infection often involves multiple sexual exposures to the virus. Even under these circumstances, however, infection is far from automatic. In a number of studies based on antibody tests, 50 to 65 percent of the regular heterosexual partners of patients with AIDS or advanced AIDS-related illness have shown no evidence of the virus in their blood. And among the wives or regular sex partners of hemophiliacs with AIDS, 90 to 95 percent were not infected.
The fact that such prolonged sexual exposure often fails to cause infection certainly argues against fears that a bathtub, toilet seat, or the air around an AIDS patient could pose a threat.
Public-health officials generally recommend using condoms during anal or vaginal intercourse and oral-genital sex to reduce the risk of AIDS-virus transmission. CDC investigators, after evaluating many studies from around the world, concluded that barrier contraceptives—condoms, spermicides, and diaphragms used with spermicides—are effective in reducing the risk of sexually transmitted diseases, including AIDS. Lubricants, if used, should be water-based; petroleum products can damage latex.
One lab experiment demonstrated that the AIDS virus can't penetrate an intact latex condom. Another showed that a common spermicide, nonoxynol-9, inactivates the virus and kills the white blood cells that carry it. (Nonoxynol-9 is the spermicide in many contraceptive jellies and foams, and the active ingredient in the contraceptive sponge Today.)
Blood-to-Blood Contact
The rapid spread of the AIDS virus among intravenous-drug users fosters the impression that the virus is highly infectious. Actually, some common practices among addicts who use needles are what make them especially vulnerable. And while there is some evidence that gay people have modified their risk behavior, drug abusers have not.
In addition to the frequency of injections—at least daily in many users—intravenous-drug addicts often share their needles and syringes. Indiscriminate sharing of injection paraphernalia has become common at drug "shooting galleries," where addicts go to rent or share equipment. "Often, the same needle will be used for up to 50 injections until it is no longer usable," reports Peter Selwyn, M.D., medical director of a drug-treatment program for addicts at Montefiore Medical Center in the Bronx, New York.
The risk of contamination is multiplied by another practice—drawing blood back into the syringe so that any remaining drug can be flushed out of the syringe and into the vein. If an addict is infected with the virus, a significant dose of it may be transmitted to the next sharer. In short, intravenous-drug use is an extremely effective way of acquiring a blood-borne disease—even one as difficult to contract as AIDS.
Some people have proposed that government agencies should make sterile needles and syringes available to intravenous-drug users, either free or at cost. Facing the threat of an AIDS epidemic in 1984, the Amsterdam (Netherlands) Municipal Health Service adopted such a plan. It appears to be working. The number of addicts using intravenous drugs has not increased, and more addicts than ever have been motivated to enter treatment for their addiction. Similar programs have since been initiated in Sweden, Great Britain, France, Italy, and Australia.
Such proposals in the United States have generally met with strong opposition. In 1988, the first attempt at a free-needle program was made in Portland, Oregon; it stalled when insurance coverage was refused. New York City began a similar program the same year. Yet even advocates of the idea recognize it as a stopgap measure. They emphasize the need for more drug-treatment centers and a multifaceted approach to the problem. But an epidemic often demands swift action. Cheap, clean needles and syringes would at least reach the inner-city battleground where AIDS has hit hardest and where the real war on drugs is being fought—and lost.
The experience of health-care workers, meanwhile, provides a striking contrast to the epidemic among intravenous-drug users. Seven separate studies in the United States and England have examined the outcome of needle-stick and other exposures among health workers caring for AIDS patients. Approximately 1500 people—nurses, physicians, medical students, technicians, and laboratory workers—were studied to determine whether their exposures had resulted in infection. Most of the exposures were needle-stick injuries from instruments that had just been used for an AIDS patient. The rest were direct exposures of a mucous membrane, such as a splash of infected blood into the eye or nostrils.
Despite the large number of exposures, only five of the 1500 workers developed AIDS-virus antibodies in their blood. Those five had experienced a severe exposure, such as a deep injection wound or a puncture from a grossly contaminated large-bore biopsy needle. None of the workers who had direct exposure of mucous membrane to blood or other body fluid developed infection.
Hemophilia, a genetic disorder marked by the absence of an important clotting factor, results in repeated bleeds, often into joints. Transfusions of blood products can correct the bleeding temporarily. Before routine screening of blood and blood products for the AIDS virus was initiated in 1985, many hemophiliacs became infected. Since then, the risk has been virtually eliminated.
Casual Contact: How Aids Is Not Transmitted
Detection of the AIDS virus in saliva in 1984, and subsequently in tears, sparked immediate public concern. But further research has shown that the virus is rarely present in either. When it is, the quantity is minute—probably too low, say most public-health experts, to play a role in infection. Nevertheless, as a precaution, they still warn against deep kissing with an infected person and advise special procedures for eye-care and dental personnel, who are constantly exposed to tears or saliva.
No such precautions apply to contact with drinking glasses, eating utensils, eyeglasses, and the like. All evidence shows that the risk from such items is nonexistent. The same is true for a typical friendly kiss.
Some parents of young schoolchildren also fear that a bite from an infected classmate might transmit the virus. Here again, the concern is unwarranted, experts at the CDC say. The amount of virus in saliva—if any—is considered too minuscule to cause infection, especially in a single instance of biting.
There is no evidence that the virus can be transmitted by food or by any variety of insect. Nurses who have administered mouth-to-mouth resuscitation to AIDS patients have not become infected. Nor have children attending school with hemophiliac classmates who were infected. But possibly the strongest evidence that the virus presents no threat in casual contact comes from studies in families.
If AIDS could spread through casual contact, a patient's home would be a likely breeding ground of infection. The close personal environment of a family household would offer ample opportunities for spreading the virus.
It hasn't happened, however. Studies in U.S. households and among families in Europe, Haiti, and central Africa have all produced the same result. No instance of transmission has occurred among anyone who wasn't the sexual partner or newborn infant of an infected person.
The most comprehensive study is an ongoing, long-term investigation being conducted jointly by the CDC, Montefiore, North Central Bronx Hospital, and Albert Einstein College of Medicine. In 1986, the research group reported its evaluation of 101 people living in households with 39 AIDS patients. None of the 101 household members were sexual partners of the patients, but all lived in close personal contact with the infected person for periods ranging from three months to four years.
"Most of the families in this study were poor and lived in crowded conditions," the researchers reported. "A high percentage of household members assisted the patient with bathing, dressing, and eating." There was close personal interaction, and substantial sharing of household facilities and items likely to be soiled with body secretions. Some of the household members used the same razors and toothbrushes as the patient. Many shared the same combs, eating utensils, plates, and drinking glasses. More than 90 percent used the same toilet, bath, and kitchen facilities as the patient, and 37 percent shared the same bed. Most also engaged in affectionate behavior with the patient, including hugging and kissing on the cheek or lips.
Except for one child infected at birth, all of the 101 households examined were found to be free of any sign of AIDS virus in their blood. The researchers concluded that transmission of the virus through ordinary personal contact "appears to be minimal or nonexistent in the household setting."
The research group has continued its investigation since that report. As of the spring of 1988, it had completed examinations of more than 200 family members in more than 75 households, including reexaminations of the original subjects. None (except the one child) showed evidence of infection.
Similar findings were recently reported from central Africa. A research group in Kinshasa, Zaire, investigated whether the same results reported among household members in Europe and North America apply under conditions common in the developing world.
"Unlike living conditions in the United States and Europe," said the report, "living conditions in households in Kinshasa are more likely to include environmental factors favoring person-to-person transmission of infectious agents." Such conditions, the report said, included "crowding, lack of modern sanitary systems, and substantial numbers of mosquitoes and other arthropods."
The study, which evaluated 204 household members of AIDS patients, found no evidence that the virus was spread by ordinary personal contact. The researchers concluded that transmission by nonsexual personal contact "appears to be very rare, if it occurs at all."
The Kinshasa group also suggested what many American and European epidemiologists have come to realize, with profound relief: Since the AIDS virus isn't spreading in the home, transmission by casual contact in workplaces, schools, or similar settings will probably never occur.
By 1985, a simple, inexpensive blood test for detecting exposure to the AIDS virus had been developed and approved for use. Called ELISA (for enzyme-linked immunosorbent assay), the test detects antibodies produced by white blood cells in response to the presence of the virus. Developed primarily to screen potential blood donors, ELISA has also served as a versatile research tool, greatly facilitating analysis of the epidemic's path.
Before ELISA, it was difficult to trace the spread of the virus. There was no practical way to detect it in people without symptoms, who represent the largest number of those infected. By mid-1988, about 65,000 cases of AIDS had been reported to the U.S. Centers for Disease Control (CDC). An estimated 325,000 people had AIDS-related complex (ARC), a term used to describe a condition that includes (in addition to laboratory evidence of immunodeficiency) swollen glands, recurrent fever, weight loss, or a combination of those symptoms. When persons with ARC develop any one of a number of opportunistic infections (or Kaposi's sarcoma), they are considered to have developed AIDS.
An estimated 1.6 million to 3.2 million additional people may be infected with the virus but have no symptoms of illness. Although their blood reveals antibodies to the virus—as determined by two consistently positive ELISA tests and a more sophisticated (and costly) confirming test called Western blot analysis—they may have no other laboratory or clinical signs of disease. Most public-health officials estimate that 30 to 50 percent of those people will ultimately develop full-blown AIDS.
With a practical means of detection in hand, researchers began probing areas previously obscure. For example, how fast was the virus spreading to the general population—or among intravenous-drug users, or gay men? Was it infecting family members who had no sexual contact with a victim in the home? Were some sexual practices riskier than others? Since 1985, a wealth of new information has become available to address those questions and others.
Some of the findings are uncompromisingly bleak. Among high-risk groups, the AIDS virus is cutting a widening swath of infection, particularly in areas that have already borne the brunt of the epidemic, such as metropolitan New York and San Francisco. The infection is also spreading among young adults in inner-city minority groups, especially black and Hispanic intravenous-drug users and their sexual partners. One analysis of blood tests administered to some 300,000 military recruits found the rate of infection in blacks to be four times that in whites.
Federal health officials have predicted that the cumulative total of AIDS cases could reach 270,000 by 1991, with 179,000 deaths. Most of those will be people who are already infected with the virus, the officials said.
The grim projections of unfolding tragedy have overshadowed all other emerging information about the epidemic. But there has been another side to the news. An increasing number of epidemiological studies now point to an unmistakable conclusion: The reassurances from health officials about casual contact with AIDS patients are well founded. As CDC director James O. Mason, M.D., put it, "This is a very difficult disease to catch."
Transmission appears to require not only direct insertion of the virus into the bloodstream but also a substantial dose of the virus—much more than could be transmitted by casual contact. Indeed, a consistent pattern in people who become infected is frequent or severe exposure to the virus.
Even in sexual intercourse—the primary route of infection—the virus does not appear to spread easily. Like most sexually transmitted diseases, AIDS is strongly associated with a highly active sex life and multiple partners.
Homosexual Transmission
Among gay and bisexual men, the disease first appeared in those with extremely large numbers of sexual partners—a lifetime average of over 1000 partners, according to one early epidemiologic study. It's not known whether multiple sexual contacts raise the risk simply by raising the odds that a person will encounter the AIDS virus once, or by some process in which the body's defenses are worn down (perhaps through exposure to other sexually transmitted diseases), or both. All that's known for sure is that having a large number of sexual partners raises the risk.
Now that the virus is more prevalent—and the odds of catching it (among people at risk) are higher—the average number of sexual partners reported by people who contract the disease would be far less than 1000. No precise numbers, however, are available.
A key factor in the rapid spread of the virus among gay and bisexual men is the practice of anal intercourse, probably because the surface membranes and blood vessels of the anal canal are vulnerable to small fissures or tears during intercourse. Such tears may allow virus carried in semen to gain entry into the bloodstream of the receiving partner. The risk of viral transmission is especially high for the partner accepting penetration (receptive anal intercourse). In one six-month study examining transmission of the virus in gay men, a University of Pittsburgh research team found receptive anal intercourse to be the major risk factor in infection. At the outset, none of the men showed any evidence of AIDS virus in their blood. After six months, however, antibodies to the virus were found in a number of the subjects, especially among men who had had two or more sexual partners. In that group, men engaging in receptive anal intercourse had 16 times the infection rate as those having no anal intercourse.
As yet, there's no scientific evidence that sexual practices other than anal-related sex lead to AIDS-virus transmission in gay men. However, only a few large studies have compared the effects of different sexual practices.
One such study was conducted by University of California researchers over a two-year period for the San Francisco Men's Health Study. The California investigators examined infection rates among some 800 gay or bisexual men with different sexual histories. No difference in infection rates was found between those who engaged solely in oral-genital sex and those who had no sexual partners at all.
The California researchers concluded that the risk of AIDS-virus transmission by oral-genital contact was minimal. But they cautioned—as did the Pittsburgh group—that their findings did not prove that sexual activity other than anal intercourse posed no risk among gay men. They pointed out that their results were based on a relatively small number of observations and could not completely exclude the possibility of transmission by oral-genital sex.
Indeed, caution has been the watchword among public-health officials offering preventive advice. Since more than 90 percent of AIDS cases have occurred in gay or bisexual men and intravenous-drug users, the message to those high-risk groups has stressed avoiding any possible risk. One drawback of that approach, however, is that it makes AIDS appear easier to catch than it actually is. Some public-health workers, for example, warn against deep kissing involving exchange of saliva. But there's no evidence that the virus is transmitted that way.
Heterosexual Transmission
In contrast to oral sex or deep kissing, vaginal intercourse is clearly an important route of infection. The AIDS virus can be spread by either a man or a woman during intercourse.
On a relative scale, vaginal intercourse appears to be less effective in spreading the virus than anal intercourse, and less contagious from female to male than the reverse. As yet, the risk of transmission in a single act of vaginal intercourse is unknown. But current evidence suggests that frequent or long-term sexual exposure with an infected partner or partners is an important factor in transmission.
As of mid-1988, about 4 percent of newly diagnosed AIDS cases in the U.S. can be traced to heterosexual transmission. A large number of the victims are spouses or long-term sexual partners of AIDS patients or other high-risk individuals, particularly intravenous-drug users. Another large segment includes immigrants from Haiti and central Africa, where the virus spreads mainly by heterosexual intercourse.
Some confusion initially surrounded the status of Haitians, who were once listed as a separate risk group for AIDS. Epidemiologists have since found that the infection rate is not high among Haitians who are longterm U.S. residents. It's high, though, among recent immigrants with a history of venereal disease or sexual contact with prostitutes. In both Haiti and central Africa, infected prostitutes are an important factor in the spread of the virus among heterosexuals.
Reports from central Africa also show that AIDS is concentrated among urban people who are very sexually active. The average AIDS patient had more than 30 sex partners a year, including frequent contacts with prostitutes.
Overall, heterosexual spread of the infection often involves multiple sexual exposures to the virus. Even under these circumstances, however, infection is far from automatic. In a number of studies based on antibody tests, 50 to 65 percent of the regular heterosexual partners of patients with AIDS or advanced AIDS-related illness have shown no evidence of the virus in their blood. And among the wives or regular sex partners of hemophiliacs with AIDS, 90 to 95 percent were not infected.
The fact that such prolonged sexual exposure often fails to cause infection certainly argues against fears that a bathtub, toilet seat, or the air around an AIDS patient could pose a threat.
Public-health officials generally recommend using condoms during anal or vaginal intercourse and oral-genital sex to reduce the risk of AIDS-virus transmission. CDC investigators, after evaluating many studies from around the world, concluded that barrier contraceptives—condoms, spermicides, and diaphragms used with spermicides—are effective in reducing the risk of sexually transmitted diseases, including AIDS. Lubricants, if used, should be water-based; petroleum products can damage latex.
One lab experiment demonstrated that the AIDS virus can't penetrate an intact latex condom. Another showed that a common spermicide, nonoxynol-9, inactivates the virus and kills the white blood cells that carry it. (Nonoxynol-9 is the spermicide in many contraceptive jellies and foams, and the active ingredient in the contraceptive sponge Today.)
Blood-to-Blood Contact
The rapid spread of the AIDS virus among intravenous-drug users fosters the impression that the virus is highly infectious. Actually, some common practices among addicts who use needles are what make them especially vulnerable. And while there is some evidence that gay people have modified their risk behavior, drug abusers have not.
In addition to the frequency of injections—at least daily in many users—intravenous-drug addicts often share their needles and syringes. Indiscriminate sharing of injection paraphernalia has become common at drug "shooting galleries," where addicts go to rent or share equipment. "Often, the same needle will be used for up to 50 injections until it is no longer usable," reports Peter Selwyn, M.D., medical director of a drug-treatment program for addicts at Montefiore Medical Center in the Bronx, New York.
The risk of contamination is multiplied by another practice—drawing blood back into the syringe so that any remaining drug can be flushed out of the syringe and into the vein. If an addict is infected with the virus, a significant dose of it may be transmitted to the next sharer. In short, intravenous-drug use is an extremely effective way of acquiring a blood-borne disease—even one as difficult to contract as AIDS.
Some people have proposed that government agencies should make sterile needles and syringes available to intravenous-drug users, either free or at cost. Facing the threat of an AIDS epidemic in 1984, the Amsterdam (Netherlands) Municipal Health Service adopted such a plan. It appears to be working. The number of addicts using intravenous drugs has not increased, and more addicts than ever have been motivated to enter treatment for their addiction. Similar programs have since been initiated in Sweden, Great Britain, France, Italy, and Australia.
Such proposals in the United States have generally met with strong opposition. In 1988, the first attempt at a free-needle program was made in Portland, Oregon; it stalled when insurance coverage was refused. New York City began a similar program the same year. Yet even advocates of the idea recognize it as a stopgap measure. They emphasize the need for more drug-treatment centers and a multifaceted approach to the problem. But an epidemic often demands swift action. Cheap, clean needles and syringes would at least reach the inner-city battleground where AIDS has hit hardest and where the real war on drugs is being fought—and lost.
The experience of health-care workers, meanwhile, provides a striking contrast to the epidemic among intravenous-drug users. Seven separate studies in the United States and England have examined the outcome of needle-stick and other exposures among health workers caring for AIDS patients. Approximately 1500 people—nurses, physicians, medical students, technicians, and laboratory workers—were studied to determine whether their exposures had resulted in infection. Most of the exposures were needle-stick injuries from instruments that had just been used for an AIDS patient. The rest were direct exposures of a mucous membrane, such as a splash of infected blood into the eye or nostrils.
Despite the large number of exposures, only five of the 1500 workers developed AIDS-virus antibodies in their blood. Those five had experienced a severe exposure, such as a deep injection wound or a puncture from a grossly contaminated large-bore biopsy needle. None of the workers who had direct exposure of mucous membrane to blood or other body fluid developed infection.
Hemophilia, a genetic disorder marked by the absence of an important clotting factor, results in repeated bleeds, often into joints. Transfusions of blood products can correct the bleeding temporarily. Before routine screening of blood and blood products for the AIDS virus was initiated in 1985, many hemophiliacs became infected. Since then, the risk has been virtually eliminated.
Casual Contact: How Aids Is Not Transmitted
Detection of the AIDS virus in saliva in 1984, and subsequently in tears, sparked immediate public concern. But further research has shown that the virus is rarely present in either. When it is, the quantity is minute—probably too low, say most public-health experts, to play a role in infection. Nevertheless, as a precaution, they still warn against deep kissing with an infected person and advise special procedures for eye-care and dental personnel, who are constantly exposed to tears or saliva.
No such precautions apply to contact with drinking glasses, eating utensils, eyeglasses, and the like. All evidence shows that the risk from such items is nonexistent. The same is true for a typical friendly kiss.
Some parents of young schoolchildren also fear that a bite from an infected classmate might transmit the virus. Here again, the concern is unwarranted, experts at the CDC say. The amount of virus in saliva—if any—is considered too minuscule to cause infection, especially in a single instance of biting.
There is no evidence that the virus can be transmitted by food or by any variety of insect. Nurses who have administered mouth-to-mouth resuscitation to AIDS patients have not become infected. Nor have children attending school with hemophiliac classmates who were infected. But possibly the strongest evidence that the virus presents no threat in casual contact comes from studies in families.
If AIDS could spread through casual contact, a patient's home would be a likely breeding ground of infection. The close personal environment of a family household would offer ample opportunities for spreading the virus.
It hasn't happened, however. Studies in U.S. households and among families in Europe, Haiti, and central Africa have all produced the same result. No instance of transmission has occurred among anyone who wasn't the sexual partner or newborn infant of an infected person.
The most comprehensive study is an ongoing, long-term investigation being conducted jointly by the CDC, Montefiore, North Central Bronx Hospital, and Albert Einstein College of Medicine. In 1986, the research group reported its evaluation of 101 people living in households with 39 AIDS patients. None of the 101 household members were sexual partners of the patients, but all lived in close personal contact with the infected person for periods ranging from three months to four years.
"Most of the families in this study were poor and lived in crowded conditions," the researchers reported. "A high percentage of household members assisted the patient with bathing, dressing, and eating." There was close personal interaction, and substantial sharing of household facilities and items likely to be soiled with body secretions. Some of the household members used the same razors and toothbrushes as the patient. Many shared the same combs, eating utensils, plates, and drinking glasses. More than 90 percent used the same toilet, bath, and kitchen facilities as the patient, and 37 percent shared the same bed. Most also engaged in affectionate behavior with the patient, including hugging and kissing on the cheek or lips.
Except for one child infected at birth, all of the 101 households examined were found to be free of any sign of AIDS virus in their blood. The researchers concluded that transmission of the virus through ordinary personal contact "appears to be minimal or nonexistent in the household setting."
The research group has continued its investigation since that report. As of the spring of 1988, it had completed examinations of more than 200 family members in more than 75 households, including reexaminations of the original subjects. None (except the one child) showed evidence of infection.
Similar findings were recently reported from central Africa. A research group in Kinshasa, Zaire, investigated whether the same results reported among household members in Europe and North America apply under conditions common in the developing world.
"Unlike living conditions in the United States and Europe," said the report, "living conditions in households in Kinshasa are more likely to include environmental factors favoring person-to-person transmission of infectious agents." Such conditions, the report said, included "crowding, lack of modern sanitary systems, and substantial numbers of mosquitoes and other arthropods."
The study, which evaluated 204 household members of AIDS patients, found no evidence that the virus was spread by ordinary personal contact. The researchers concluded that transmission by nonsexual personal contact "appears to be very rare, if it occurs at all."
The Kinshasa group also suggested what many American and European epidemiologists have come to realize, with profound relief: Since the AIDS virus isn't spreading in the home, transmission by casual contact in workplaces, schools, or similar settings will probably never occur.
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