Text: Bertrand Tappy

Viruses, those tireless globetrotters

From the FLU to HIV, a virus that causes the same illness is never perfectly identical everywhere on the planet. Researcher Séverine Vuilleumier devotes her time to studying the virus populations roaming around the globe and what they can tell us.

Despite all the media attention, human immunodeficiency virus (HIV) still holds many secrets for scientists and the general public. For example, did you know that there are several sub-types of the virus, which can mix with one another to form yet more strains? In fact, 72 “recombinant” forms of HIV are at the root of pandemics.

Until 1996, only two recombinant versions had been identified. And scientists were convinced that they never combined with each other. “We now know that’s false,” says Séverine Vuilleumier, a scientist from the Institute of

Microbiology at the Lausanne University Hospital. “When the viruses meet, they engage in battles, and science can learn a lot from them.”

Our knowledge about this behaviour has grown so fast thanks to the development of genomics, which can be used to map out the precise genetic code of living organisms, including viruses. “Today, we know about a wide catalogue of forms of the AIDS virus,” Séverine Vuilleumier says. “What interests my team more specifically is studying the migratory movements of these virus types and sub-types to determine their history, origin and strength. If a given form A meets another form B, who wins? What will come of that encounter? The answers to

these questions will provide precious information, for example in searching for a vaccine.”

Séverine Vuilleumier has been studying these complex migration patterns for many years. Early in her career, the biologist studied extinctions and emergences of animal species. She believed that their migration patterns could explain why some

of them disappeared. Later, the scientist began looking at viruses, which she thinks are “interesting because they evolve much faster and are easier to observe.” This research eventually caught the attention of the Faculty of Biology and Medicine at the University of Lausanne (UNIL) and the Swiss National Science Foundation, which financed the next phase of her work.

In addition to predicting the evolution of HIV around the world, this study of the migratory behaviour of viruses has already pinpointed the type of virus that was first transferred from animals to humans, and therefore the place. “Animals are rarely sick after contracting SIV [simian immunodeficiency virus, the animal form of HIV],” Séverine Vuilleumier says. “And the same goes for other viruses like Ebola, another pandemic that drove the scientific community to look into the subject. The mechanisms behind the emergence of a given version of the virus over another have yet to be discovered,” she continues. “These recombinations generally weaken the virus, but unfortunately the microorganism can also become much, much stronger. Ironically, that’s not always good news. If the virus becomes too powerful, it can kill its host and therefore bring about its own demise.”

Many of our old certainties about HIV have already been challenged by the discoveries made by these new “genomic cartographers”, including Séverine Vuilleumier and her team. The next step is to develop strategies to control or even slow the evolution of the virus and the pandemic. “I started out studying animals and ended up focusing on viruses. It’s an excellent way of moving back up from the microscopic to the human scale,” Séverine Vuilleumier says mischievously. And she seems more motivated than ever to yo-yo back and forth between the immense and the immensely small. ⁄



Group M of HIV-1 is the most common type of the virus in the world. It is responsible for the AIDS pandemic

and has infected nearly 40 million people. New recombinant forms of HIV Group M still emerge today.

Various forms of hiv throughout the world

HIV features high genetic diversity. Two major types of the virus have been identified: HIV-1, the most common strain in the world, and the less contagious HIV-2. Each type is made up of several groups, which can fur- ther be divided into sub-types.

The AIDS virus originated in primates in the Congo Basin at the beginning of the 20th century. It is believed to have spread to humans around the 1950s. HIV began to migrate in its different genetic variations to other regions of the world in the 1960s. The microbiologist Séverine Vuilleumier specialises in studying the consequences of these migratory movements of the virus.