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Newly infected spread half of HIV
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McGill study finds high-risk people often don't know they have virus
LISA PRIEST
From Friday's Globe and Mail
Half of all new HIV transmissions occur when people are unlikely to know they carry the virus and in some cases, wouldn't test positive for it because they are so newly infected, a Canadian study says.
The study, to be published in the April edition of the Journal of Infectious Diseases, is one of the first in the world to quantify how many of the newly infected are responsible for spreading the disease to others.
And it raises troubling questions about how to deal with the problem: How can those at high risk be encouraged to come forward and undergo frequent, repeated tests when no one knows who they are? And should those at very high risk of contracting the disease be put on anti-retroviral therapy as a preventive measure?
"From the standpoint of public health, we have a major problem in Canada and North America," study author Mark Wainberg, director of the McGill University AIDS Centre at the Jewish General Hospital, said in a telephone interview yesterday.
". . . One of the things driving this entire epidemic is that people themselves are newly infected and are often the most infectious they will ever be throughout their lives and often not even know it."
Those who have just become infected with HIV are at their most infectious as the virus madly replicates, making millions of copies. The immune system responds by launching a battle on the virus and making antibodies.
Those going through this process, medically referred to as seroconversion, report flu-like symptoms, including fever and chills. Others, however, feel no differently.
Most people, after being exposed to the virus, would test positive for it two to four weeks later; others may not test positive for the virus that causes AIDS until three and as long as six months later, said Rita Shahin, associate medical officer of health with Toronto Public Health.
"This is an important study," said Dr. Shahin, who was not involved in the research. "We've always known that people who don't know their HIV status are accounting for a significant percentage of transmissions. This further narrows it down to that group who are within the first six months of infection."
She recommended testing of high-risk individuals every three to six months. Other efforts have included putting condoms in bathhouses, counselling and education.
Dr. Wainberg said those who learn of being HIV positive often modify their behaviour so as not to put others at risk.
But modifying behaviour is not necessarily an option when someone does not even know or suspect they have the disease.
At the end of 2005, an estimated 58,000 people in Canada were living with HIV infection, including AIDS. This represents an increase of about 16 per cent from the 2002 estimate of 50,000. Of those, 27 per cent would be unaware of their infection, according to Public Health Agency of Canada figures.
An accompanying editorial to the journal article, also posted online, stated it is time to evaluate the most potent intervention to treat the disease -- highly active anti-retroviral therapy -- as a form of prevention.
"HAART is no replacement for enhanced behavioural approaches to reduce transmission," the editorial says. "It is expensive, and relatively toxic, and many regions of the world still have not implemented therapy to many of their infected populations. However, we argue that the current focus on increasing HIV diagnoses through more widespread testing requires a parallel strategy for minimizing ongoing transmission."
However, the editorial goes on to say "it is now time to evaluate application of the most potent intervention to treat this disease -- namely, an anti-retroviral therapy -- to its prevention."
Dr. Wainberg agreed with the sentiment, saying that there are clinical trials under way to determine whether the drugs to treat the disease can be used to prevent transmission among very high-risk groups, such as sex workers in the developing world.
"We know through a study that came out a month ago that microbicides are not yet ready for prime time," he said in a telephone interview from Los Angeles, where he was attending a conference. "A related concept is giving them drugs orally as preventives."
He also recommended that public-health officials try to identify high-risk people and encourage them to be tested, as well as providing more rapid testing.
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