HIV - Treat to prevent?

posted: 06/04/2010

The use of HIV treatment for preventing HIV is a hot – and controversial – topic. Now researchers are saying people with HIV should not stop using condoms and start depending on HIV treatment to protect their partner until you have taken treatment and the viral load has been undetectable for at least 12 months.

 
Some, perhaps most, people who are taking HIV treatment, who do not have sexually transmitted infections and who have an undetectable viral load, are not infectious to their sexual partners.

Some of the research suggests that taking HIV treatment and keeping an undetectable viral load is at least as good as using condoms in preventing HIV. Not everyone agrees, and there are heated debates about this at HIV conferences.
 

The debates started about two years ago with what is now called the Swiss statement - it was followed by broadly similar statements from France, Germany and the USA.

Reliably undetectable?
Danish researchers wanted to see if people taking HIV treatment can rely on their viral load remaining undetectable. They looked at the viral load results of every person in Denmark who was taking HIV treatment. Research shows that HIV transmissions are very rare if a person had a viral load below 1000 copies/ml. So they assumed that everyone taking HIV treatment with a viral load above this is potentially infectious. They then calculated the amount of time that people taking HIV treatment had an ‘infectious’ viral load of above 1000.
 

Reliable for most

For people who reached an undetectable viral load, it stayed undetectable 99.5% of the time.
But during the first year of HIV treatment, viral load can suddenly increase to detectable levels – this happens for about 5% of the time. People won't know when their viral load has taken an upward, detectable, blip when HIV transmission becomes more likely.

The risk of transmission was especially high during the first six months of HIV therapy, when 8% of the time was spent with a viral load above 1000 copies/ml. During the next six months, viral load was at potentially infectious levels for a little over 1% of the time. After the first year viral load was only above the potentially infectious threshold for an average of 0.6% of the follow-up period. After five years, only 0.03% of the follow-up period was above 1000 copies.

Different routes of transmission do not seem to make a difference - except for injecting drug users who had a potentially infectious level of viral load 1.5% of the time. The researchers belive this is because of poorer treatment-taking among injecting drug users.

Wait until viral load stays undetectable for 12 months

They therefore think that the Swiss recommendation about using treatment for HIV prevention should be tightened. They believe people should not swop condoms for treatment until there has been an undetectable viral load for at least twelve months, twice as long as suggested in the Swiss statement.
 

Sexual Transmitted Infections and viral load

Sexually transmitted infections can cause undetectable viral loads to suddenly become detectable - especially in the genital fluids. We measure all our viral load samples from the blood but what passes on HIV is HIV in the genital fluids. Many people have undetectable HIV in the blood but can have a detectable viral load in the genital fluids - and these are the ones that transmit HIV in sex. Sexually transmitted infections cause detectable genital viral loads and make us more infectious. Some experts say that among groups of people with high rates of sexually transmitted infections, such as gay and bi men with HIV, undetectable viral load is too unreliable to judge your risk of passing on HIV.

Swiss reminder

The debate on treatment as prevention was kick-started a little over two years ago by the release of what is known as ‘the Swiss statement.’
Senior Swiss HIV doctors and researchers said that HIV-positive individuals who were taking HIV treatment were not infectious to their sexual partners if:

• Their viral load had been undetectable for at least six months.
• They took their HIV treatment properly.
• They did not have any sexually transmitted infections.

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