The discovery of a more dangerous variant of the HI virus in the Netherlands shows that pandemic viruses do not automatically become milder over time. A team led by Chris Wymant from the University of Oxford identified a group of 109 people who were or are infected with a more contagious and twice as aggressive version of HIV, the causative agent of the immunodeficiency disease AIDS. As the team reports in Science, the variant provisionally known as VB (virulent HIV subtype B) reproduces better in the body. Those affected had 3.5 to 5.5 times more virus in their blood than a comparison group infected with common versions of subtype B. The higher viral load facilitates transmission of the virus.
At the same time, the number of T cells in the patients – a measure of the severity of the disease – fell twice as fast as in the comparison group. And not just because the virus multiplies more strongly in these cells: VB is intrinsically more deadly for T cells and thus probably also for humans. If left untreated, AIDS will develop in the new variant in two to three years, instead of six to seven years as was previously the case. However, the new variant is not a public health crisis, writes the HIV researcher Joel O. Wertheim, also in “Science” – it can be easily controlled with proven measures. However, the knowledge gained is relevant for the future development of Sars-CoV-2.
The variants Alpha and Delta, like VB, proved to be both more contagious than their progenitors and cause more serious illnesses. The background here is probably the higher viral load, which makes people more contagious and sicker at the same time. How dangerous Sars-CoV-2 is in the long term depends on whether there is a correlation between improved infection and more severe diseases and what it looks like under different conditions.