An aggressive HIV variant silently spread in the Netherlands for 2 decades — a cautionary tale for the current pandemic

• An aggressive HIV variant has been spreading in the Netherlands since the 1990s.
• European researchers recently identified more than 100 people with the variant dating back to 2003.

European researchers recently detected something unusual about a cluster of HIV cases in the Netherlands: More than a dozen people with HIV infections had high amounts of virus in their bodies, suggesting their infections could progress quickly to AIDS if they didn't seek treatment right away.

That was just the beginning. After scouring a database of HIV patients, the researchers identified 109 people in total with identical or near-identical genetic sequences, dating back to the 1990s.

The group had all been infected with an aggressive HIV variant the researchers called "VB" in reference to the variant's lineage. The variant belongs to subtype B, a widespread group of HIV strains.

In a study published Thursday, researchers at the University of Oxford determined that VB had been lurking undetected in the Netherlands for two decades. While the first known case was diagnosed in Amsterdam in 1992, cases in the study are from 2003 onward.

"It was spreading since the 90s, just like every other strain of HIV out there. It was just spreading faster than other strains of HIV," Joel Wertheim, an associate adjunct professor of medicine at the University of California, San Diego, who wasn't involved in the research, told Insider.

The discovery of VB took so long, he added, because the cases didn't seem out of the ordinary, though they presented as more severe than many HIV infections.

"You have to sequence the viral genome and build these viral family trees and, once you do that, this variant stands out against all others," Wertheim said.

The study underscores an important lesson for the coronavirus pandemic: Any virus that's spreading can mutate, and a mutating virus can evolve to become more lethal.

"We saw the same thing with the Delta variant," Wertheim said, adding, "It was more transmissible and more virulent. There's a general mistaken assumption that, in the long term, all viruses will evolve to be benign. That's simply not true and this study stands in stark contrast to that idea."

HIV drugs still work against the variant, despite its virulence

Without treatment, VB seems to cause more severe disease in a shorter amount of time than other common HIV variants.

Most people with HIV are vulnerable to developing AIDS around six to seven years after they're diagnosed, assuming they don't seek treatment, the researchers wrote. But people with VB could develop AIDS within two to three years if the variant goes untreated.

Among men in their 30s, the variant could progress to advanced HIV just nine months after their diagnosis, the study found. By contrast, men in their 30s who contract other variants typically don't develop advanced HIV until three years after their diagnosis. Both scenarios assume the men haven't received treatment.

Fortunately, VB responds to the same virus-blocking drugs as other HIV strains.

The researchers didn't detect large differences in mortality between people who contracted the variant and those who contracted another HIV strain, most likely because people with VB started treatment shortly after their diagnosis.

However, the researchers expressed concern about areas outside the Netherlands where HIV screening is less common. In some parts of the world "the probability of reaching advanced HIV before diagnosis would be even greater," they wrote, since people could be diagnosed much later in the course of their infection.

HIV has evolved at a much slower rate than COVID-19

While the VB variant has been spreading for decades, it hasn't torn through populations quickly.

"HIV operates on a much slower time scale than, say, our current pandemic," Wertheim said. "Evolutionary change is going to happen over the course of years and decades, as opposed to Omicron, which swept through the world in a matter of months."

There's still a lot that researchers don't fully understand about the variant, though, including why it emerged in the first place.

The study's models suggest VB grew more prevalent until around 2010, then potentially started to decline, although the researchers caution there's a high degree of uncertainty about the trend.

Wertheim said there's still a question of whether VB will persist into the future.

In a paper published Tuesday, Wertheim argued that maintaining some level of virulence is crucial to HIV transmission, since virulent strains produce high viral loads, giving the virus more opportunities to transmit before a patient seeks treatment. But he noted that HIV infections have followed a different evolutionary pattern from one region to the next.

"In some places in the world, like in Uganda, HIV seems to be evolving to be less virulent," Wertheim said. "Here in the United States, we've seen over the decades, HIV seems to be getting slightly more virulent and transmissible. And now we have this example in Europe of HIV evolving [toward] increased virulence."