WEDNESDAY, Nov. 27, 2002 (HealthDayNews) -- For the third reported time this year, an AIDS patient has come down with a second strain of the disease. The development gives more credence to the theory that HIV-positive people are susceptible to so-called "superinfection," even if they've kept the initial virus attack under control.
Experts fear that superinfection -- essentially, a double infection with two different types of AIDS -- could become more common if more HIV-positive people have sex with each other.
"The bottom line is that even consenting partners who are both infected should practice safe sex," said Dr. Bruce D. Walker, a researcher at Harvard Medical School, who co-wrote a letter to the editor in tomorrow's issue of the journal Nature about the double-infected patient.
According to Walker, doctors had long thought that AIDS patients could only be infected with one strain of the disease. But doctors reported two previous cases of superinfection earlier this year. With the third case being reported, "we now know that this can happen, even when the two strains are very similar," Walker said. "But we do not yet know how frequent superinfection is."
The case discussed in the letter is especially worrisome. Unlike the two earlier reports of superinfection, it occurred in a patient who was doing fairly well on drug treatment, Walker said. Also, the two other cases involved very different types of strains of HIV, the virus that causes AIDS. The new case, in which a patient was infected by similar strains, suggests that resistance to one strain won't prevent infection by a nearly identical other one.
The patient had undergone an unusual form of drug therapy in which he rotated on and off AIDS medications. Some patients can do that, but only if they start the drug treatment shortly after infection with HIV, said Michael Allerton, HIV operations policy leader for the Kaiser Permanente Health Plan in Northern California.
"It's important to distinguish this from someone who has been infected for a long period of time," Allerton said. "Once you've gone on medication (late in the infection), trying to stop [discontinue] the drugs has proven to be a dismal failure."
Even though he was doing well under his AIDS treatment, the patient was infected by another strain of HIV, one that was very similar to the one he already had.
The patient said he had a casual sexual encounter about a month before he reported a bout of fever and night sweats. Those are symptoms that are frequently signs that the body is fighting off a new HIV infection.
The findings pose more challenges for researchers who are developing an AIDS vaccine, Allerton said. If similar strains can attack one person, a vaccine that protects against one won't always be effective against the other.
People infected with HIV should consider the risks when they have sex with other HIV-infected people, even in monogamous relationships, he said.
Even if both partners are infected with the same strain of HIV, "it's not known whether you can be infected with the same strain over and over again," he said.
The patient's case also spells trouble in another way: It suggests that AIDS patients could be susceptible to superinfection by HIV strains that are immune to the drugs they're taking. Drug resistance is a growing problem among AIDS patients, forcing doctors to try a variety of medications before they can find one that works.
"Even though they might be (properly) taking their own medicines and have a virus that is fully sensitive to the drugs, through unsafe sex they could become infected with a drug-resistant virus," Walker said.
What To Do
To learn more about HIV/AIDS and treatments, visit the Centers for Disease Control and Prevention or the National Institute of Allergy and Infectious Diseases.