HIV in its early stages is less infectious than thought: study

A new study co-authored by a McMaster University researcher has found that people who have recently contracted HIV may not be as infectious as previously thought — a notion that could influence treatment plans in Third World countries.

As HIV researchers debate the best way to combat the virus's spread in sub-Saharan Africa, one phase in the virus's development poses a special challenge: the very early onset of HIV. The trouble with that phase, researchers say, is that a person who has contracted HIV in the past few weeks may not know he or she has it. It has been widely assumed that the virus is extremely contagious at that point. 

But the new study shows that previous research "substantially overestimates" how infectious that early stage of HIV is. A McMaster University infectious disease researcher is one author on the study that re-analyzes the only available direct research on infectiousness in that phase.  

We found that passing HIV to another person isn’t as likely to happen during this stage as people have been assuming for many years.- Dr. Steve Bellan, University of Texas at Austin 

The findings have implications for a popular, promising public health tool for combatting HIV's spread: "treatment as prevention." The idea is that modern antiretroviral drugs are so powerful that they can significantly drop the infectiousness of a person with HIV before it develops into AIDS, the researchers say.

There has been push back on implementing that tool widely in Africa and other places that need the help. If the early-phase infected patients are still highly infectious, they may not be getting treatment in time to curb the disease's spread, and so the costly drugs may not be worth the investment. 

But the study, led by University of Texas at Austin researcher Steve Bellan, pokes holes in the assumption of how infectious the early-stage HIV patients are. Jonathan Dushoff, a McMaster associate professor of biology at the Michael G. DeGroote Institute for Infectious Disease Research, and researchers from Yale University were also part of the study, published Tuesday in PLOS Medicine. 

"Elevated infectiousness early in infection alone is unlikely to undermine treatment-as-prevention campaigns," the study says.

Most of what we know about this phase of HIV infection comes from one study of 23 heterosexual couples in Rakai, Uganda, the study said. With the new report, researchers re-analyzed the data using new models and factors that weren't considered for that original paper.

"We found that passing HIV to another person isn’t as likely to happen during this stage as people have been assuming for many years," Bellan said in a media release. "That fact would be cause for optimism when it comes to novel interventions that aim to curb HIV’s spread."

Dushoff called the original study a "once-in-a-lifetime data set." 

"It's amazing," he said. "It's amazing that they were able to estimate this ethically."

Now Dushoff, Bellan and their team aim to get the analysis of that data "as right as possible," Dushoff said.

'A result taken for granted for a decade'

Cornell University infectious disease researcher Laith J. Abu-Raddad wrote a perspective on the new study, also in PLOS Medicine.

The new report "has shaken our faith in a result taken for granted for a decade," Abu-Raddad said.

"Bellan and colleagues’ analysis provides a cautionary tale. It took a decade to realize that the estimates of acute infectivity were inflated, and this could have been avoided."

Abu-Raddad said the study's new estimates of infectiousness in that early stage may make the promising "treatment as prevention" approach 5 per cent more cost effective.

"Such a small increment may have still significant budgetary implications," Abu-Raddad said. "It might be time to focus on [treatment as prevention] as the best strategy to get these epidemics under control, at least for the time being."

'I don't know which estimates are "true"'

One of the original Rakai study's authors, Johns Hopkins University researcher Ronald Gray, said he reviewed the new study and corresponded with Bellan before it was published. The new study's complex mathematical analysis makes it difficult for him to follow the new study's findings, he said.

"I am always skeptical of modeling studies based on secondary data analysis because they are vulnerable to error in underlying assumptions," he wrote to CBC Hamilton. "So the bottom line is that I don’t know which estimates are 'true'."

Caution is required for basing policy on the new study, Gray said, and the infectiousness of the early stage HIV is not the only roadblock to its effectiveness.

"Nevertheless, 'treatment as prevention' is being implemented, at least in high risk populations, and we will hopefully find out whether it works in the real world," Gray said. "There are a lot more potential obstacles to success than the rate of acute transmissions."