Friday, September 24, 2010

Unsafe Health Care and Risk of HIV Transmission

Frederik Joelving, in an article entitled ‘Did Doctors Jumpstart the HIV Pandemic?’, looks at the recent research which finds that public health programs carried out 50 to 80 years ago may have played a part in spreading HIV. I mentioned this research recently. But it’s interesting to hear what the scientists involved have to say to a journalist.

According to Joelving, “What is still a matter of debate is how a blood-borne disease infecting one or a few individuals in a remote area could ever spread to the more than 33 million people who were infected by 2008, and kill two million of them.”

However, Thomas Strickland, one of the researchers, says "Everybody now is getting infected from having sex”. This is not the case. HIV has never been entirely sexually transmitted and the extent to which it is sexually transmitted is not known.

Worse still, Strickland goes on to say that sexual transmission is not very efficient and that “You can have heterosexual sex ten or fifteen times without getting infected.” Heterosexual HIV transmission is far less efficient than that. Transmission risk is very contentious but estimates run into hundreds or even thousands of sex acts (Risk of transmission of HIV varies from 1 in 200 to 1 in 10 000 coital incidents, depending in part on the integrity of the vaginal epithelium.)

Strickland is right in stating that “if you get injected with a contaminated needle, the risk is much higher”, but he seems to assume that the chances of being injected with a contaminated needle nowadays are pretty low because standards of hygiene are high. Standards are not high in many countries, Kenya being just one.

It’s a pity that this research has been interpreted so narrowly but there are even narrower views. One Michael Worobey blames urbanization and prostitution for the eruption of HIV from a rare virus to a global pandemic, whereby “an infected villager made his way to the city, setting off the HIV epidemic like a spark falling on a dry savanna.” Worobey goes on: "I think a train is a much better way to get a virus to a city than a needle".

Somehow, I think a needle is of far more danger than a train when it comes to spreading viruses. As for the urbanization explanation, this just doesn’t wash. In a paper entitled ‘Spatial phylodynamics of HIV-1 epidemic emergence in east Africa’, the authors conclude that migration, population growth and warfare contribute marginally to the spread of HIV.

The authors do show that transport infrastructure was vital to the spread of HIV over long distances. But they don't show that once the virus arrives in distant places, that it must have been spread sexually.

Jacques Pepin feels that both reuse of needles and sexual transmission are compatible and that both probably contributed to the pandemic. But he argues that “single use needles are now commonplace” and that “unprotected sex is the major reason people get HIV”. Perhaps he doesn’t read publications from the WHO (though who could blame him?).

Sexual transmission is, as mentioned, not very efficient. There is a limit to the amount of sex and sexual partners a person can have. Their chances of having a HIV positive partner may increase as an epidemic spreads. But even if someone had hundreds of sexual partners a year, the risk per sex act is still low. In other words, most people will only transmit HIV a small number of times through heterosexual sex, if at all.

In contrast, if a hospital or clinic is giving injections with unsterilized equipment, the risk of infecting patients is many times higher than the risk of sexual transmission. Not only that, a single health practitioner can potentially infect many people per day, week or year. People infected through unsafe health care can also transmit HIV sexually, though they are no more likely to do so than those infected sexually. And every HIV positive person treated in a health facility that engages in unsafe practices can give rise to more HIV transmission. The potential for health care transmission is of a different order of magnitude than that for heterosexual transmission.

Research to quantify the contribution that unsafe health care makes to HIV epidemics in African countries would not require groundbreaking techniques. Normal infection control investigations should be able to establish levels of unsafe practices in hospitals and clinics and measures to reduce such practices are well known in Western hospitals. But even researchers doing groundbreaking work seem unwilling to upset the orthodoxy.


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