Public Release: 

HIV Transmission Through Oral Sex May Be Common; Doctors Often Miss Early HIV Diagnosis

University of Washington

Good and Bad News in Battle Against AIDS
Good and Bad News in Fight Against AIDS

There is both good and bad news in the ongoing battle to stem the AIDS epidemic, a University of Washington study shows.

On the one hand, patients recently infected with the HIV virus reported they had far fewer sex partners in the months prior to infection, compared to people in similar circumstances a decade ago.

However, researchers found that among 46 patients who had acquired the virus since a recent earlier screening:

  • Acquisition of HIV infection occurs even among those with relatively few sexual partners;
  • Unprotected oral sex is the most common form of sexual contact among gay men who become HIV-infected;
  • Among people able to pinpoint the specific sexual contact that led to infection, oral sex was the possible route of transmission in some cases;
  • Seven percent of patients reported they had actively tried to acquire the HIV virus;
  • Even among patients who identified themselves at high risk for acquiring HIV and who went to their doctor with clinical symptoms at the time of transmission, only one-quarter were correctly diagnosed with acute HIV infection.

The study, undertaken to describe events that lead to HIV infection, was conducted by Dr. Timothy Schacker of the Virology Division of the UW Department of Medicine, and colleagues Dr. Lawrence Corey, Dr. Ann C. Collier, Dr. James Hughes and Theresa Shea. The study is reported in the Aug. 15 issue of The Annals of Internal Medicine.

Enrolled in the study were 43 men and three women who had acquired symptomatic HIV in the recent past, as documented by a negative screening test in the previous few months. All but one of the men reported sexual contact with other men as their principal risk behavior. (The three women reported heterosexual contact as their primary risk behavior.)

Four men reported only oral-genital contact. Schacker acknowledged that since his subjects were interviewed in person, they could have been less than candid. However, they were interviewed numerous times and their responses on sexual behaviors did not vary. The source partners of two of the four confirmed the descriptions of sexual activity.

The finding on oral-genital contact may be of special interest, notes Schacker, in light of a study reported June 7, 1996 in the journal Science by Dr. Ruth Ruprecht and colleagues at the Dana-Farber Cancer Institute in Boston, that showed an oral dose of semen from a rhesus monkey infected with the SIV (monkey AIDS) virus infected six of seven monkeys, even though their mouths were free of lesions.

"Despite warnings from health experts over the years, many advocacy groups have maintained that unprotected oral sex is a safe alternative to anal or genital intercourse," said Schacker. "The results of these and other studies show that oral sex may not be as safe as previously thought."

Unprotected oral-genital contact was the most commonly reported sexual activity. The subjects reported a median of 20 oral-genital contacts in the six months prior to acquiring HIV, versus two anal-genital contacts. Fewer than 4 percent of oral-genital contacts involved a barrier form of protection, while 42 percent of anal-genital contacts involved a condom.

Almost half the patients reported they had sexual contact with only one partner in the month before acquiring the virus, and a median of three partners in the six months infection. These figures show that a pattern of sequential monogamous relationships can lead to HIV infection, the researchers say.

Three men said they had intentionally engaged in unsafe sexual behavior to try to become infected with HIV, because they felt depressed and excluded from their peers, many of whom had AIDS.

In another finding, even among men undergoing routine screening for HIV at four- to six-month intervals (indicating they knew they were at risk), a correct diagnosis of acute HIV infection was made in only five of 19 patients who went to their doctor with symptoms.

"The symptoms may make it difficult to differentiate from other illnesses," said Schacker. "Many patients go to one clinic for anonymous HIV testing, and to another for routine medical care. The caregiver may be ignorant of a patient's risk factors for HIV and thus not recognize or correctly diagnose symptoms.

"Health care providers need to maintain a high index of suspicion for symptoms suggestive of primary HIV," said Schacker, adding that an adequate sexual contact history should be taken when sexually active patients visit emergency rooms or clinics with fevers, sore throats or symptoms of mononucleosis or viral meningitis. "We recommend testing with a P24 antigen or HIV RNA and HIV antibody test in all high-risk patients who have symptoms compatible with acute HIV infection."

The researchers add that diagnosing recently acquired HIV infection may be important for several reasons. In the first few weeks after infection, the amount of virus in the blood (and presumably semen) is the highest it will ever be, which may make it easier to transmit the infection to others. Transmission of the virus in the period even before diagnosis was documented in several patients.

Early diagnosis can also facilitate rapid initiation of treatment, which becomes increasingly important as new therapies are developed.

The researchers give several caveats about the study. Subjects were referred to the UW research clinic conducting the study, and thus were more likely to have symptoms. It involved mostly men who acquired HIV through sexual contact, so results cannot be generalized to the entire population of HIV-infected persons. The study also does not provide insight into how HIV is acquired in women or through intravenous drug use.

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