A 'Highly Virulent' HIV Strain Is 'No Cause for Alarm,' Scientists Say

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An international research team has identified a highly virulent and infectious strain of HIV that likely began circulating in the Netherlands in the 1990s and has infected more than 100 people.

Left untreated, this viral strain leads to a much higher level of virus in the blood and a doubled rate of decline in key immune cells compared with the typical HIV disease progression.  

The research team, led by scientists at the University of Oxford with key contributions from Stichting HIV Monitoring in Amsterdam, has stressed that these findings are not cause for alarm. This particular HIV strain responds well to antiretroviral treatment, which has the added benefit of blocking transmission. While the strain could still be transmitting to new people, once someone with the strain starts treatment, it is not associated with an increased risk of illness or death.

Dr. Douglas D. Richman, a clinical virologist at the University of California, San Diego, who was not involved with the study, praised the new paper, published Thursday in Science, as “the first compelling description of an HIV variant that appears to be more virulent.”

“The most important take-home lesson is, it’s not like a new omicron variant here and that we’re going to have a new wave of some terrible problem,” Richman said.

Michael Emerman, a virologist at the Fred Hutchinson Cancer Research Center in Seattle, nevertheless expressed concern about the paper’s potential impact on the popular imagination, anticipating “that it’s going to be interpreted that there’s a deadly super-HIV strain.”

There is precedent for how communicating about the HIV epidemic can cause needless public panic.

In 2005, researchers in New York City discovered that a local gay man had recently contracted an HIV strain that they believed was both highly virulent — he became sick with AIDS no more than 20 months following infection — and broadly resistant to the antiretroviral treatments available at that time. The man reported habitual crystal meth use and frequent sex without a condom with multiple partners.

Dr. Tom Frieden, an infectious disease physician who was then the commissioner of the New York City Department of Health and Mental Hygiene and was later appointed director of the Centers for Disease Control and Prevention, held a February 2005 news conference announcing the findings and warning that this man’s case could portend a grave threat to public health. The announcement ignited a global panic over the so-called superbug, a situation the authors of the new paper are keen to avert.

In the end, the virus in the New York City man responded well to treatment, and no other cases of such rapidly advancing HIV were identified.

As the Covid-19­-weary public has learned through the emergence of new coronavirus variants, viruses are always evolving. Chance mutations will at times lend a selective advantage to a virus. Then the new, mutated version can spread more widely as a result.

The authors of the new paper initially identified 17 individuals, all members of a study of people living with HIV in Europe and Uganda, who had unusually high viral loads following diagnosis. Fifteen of them were also registered in a separate cohort study based in the Netherlands, while one person lived in Belgium and another in Switzerland.

Next, the investigators cast a wider net, examining 6,706 blood samples from people with HIV participating in the separate Dutch study. There, they found an additional 92 people who, according to genetic analyses, were all living with a closely related, highly virulent HIV strain.

Signs suggest this strain might not have spread much outside the Netherlands. The researchers determined this by analyzing samples from a large study of people living with HIV in Switzerland — a cohort that covers about 90 percent of the nation’s diagnoses since 2009. There, they only found three people with the related viral strain, including the one previously identified Swiss individual.

Analyzing the pre-treatment disease trajectory of the 109 people with the related HIV strain in question, the scientists observed a viral load that was typically 3.5-fold to 5.5-fold higher compared with 6,604 other people in the wider cohort study who had the same HIV subtype but a different strain. (An HIV subtype is a broader genetic category than a strain.) The doubled rate of decline in CD4 immune cells seen in those with the especially virulent virus, a statistical analysis indicated, occurred independently of the high viral load.

Based on these findings, the investigators projected that without treatment, people with the highly virulent HIV strain would likely develop AIDS within just two to three years of diagnosis, compared with the more typical six to seven years expected in the comparison group.

The overall characteristics between the two groups were similar when it came to their age, sex, suspected mode of HIV acquisition and place of birth. This helped the investigators conclude that hundreds of mutations to the virus’s genetic code were likely responsible for the strain’s increased potency and infectiousness, not the genetics of the people who contracted the strain or environmental factors such as nutrition or other infections.

The earliest evidence of this strain was in an individual diagnosed with HIV in 1992. It would then spread silently in the Netherlands for decades before the authors of the new paper, armed with cutting-edge tools they had a hand in developing for analyzing viral genetics, would detect it.

Eric Hunter, a molecular virologist at the Emory Vaccine Center in Atlanta who was not involved in the study, said he looked forward to future research of this HIV strain that might reveal further insights into its origins and disease trajectory.

“It would be particularly interesting to understand what was the viral or molecular basis for that more rapid disease progression in these individuals,” Hunter said.

Chris Wymant, the new study’s lead author and an epidemiologist in the department of medicine at the University of Oxford, reiterated that his team’s findings are “no cause for alarm.”

Wymant noted that broadly adopted guidelines for tackling the global HIV epidemic — widespread testing and immediate initiation of treatment following diagnosis — could help identify anyone who might contract this viral strain and ensure it did not disproportionately impact their long-term health prospects.

An estimated 38 million people are living with HIV worldwide, about 1.2 million of whom are in the United States, according to the Joint United Nations Program on HIV/AIDS and the CDC. There are approximately 1.5 million HIV transmissions globally each year, including about 37,000 new U.S. cases.

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