With several dozen cases detected in humans in North America, does the H5N1 avian flu virus represent the next big pandemic threat?
The fact that this virus, which originally only affected birds, has spread to other species, including mammals, worries us. But, for the moment, there have only been transmissions from animals – cattle or poultry – to humans, and not between humans, which is reassuring. Another reassuring element is that most cases are mild. Out of 66 people infected, there were only two severe forms, in Canada and Louisiana. Certainly, this last patient died. However, it should be noted that he was over 65 years old and suffered from comorbidities.
We have also seen contamination in humans in Asia in recent years, with high fatality rates. Should we be worried?
Indeed, a resurgence of human cases of infections has been reported in Cambodia. Between February 2023 and January 2025, 20 people tested positive there, following confirmed or suspected exposure to wild birds or domestic poultry. A 28-year-old man died on January 10 after ingesting infected poultry. Note that the virus circulating in Cambodia is not the same as in the United States. We must also be careful when we talk about high case fatality rates because we do not generally identify all cases and we mainly detect those which are serious. The Cambodian authorities and the Pasteur Institute of Cambodia, in particular, are monitoring the situation very closely.
It would only take one or two mutations to the H5N1 virus which is prevalent in the United States for it to be adapted to humans and able to be transmitted between humans. How likely is this to happen?
I can’t tell you what the probability is. On the other hand, what we observed was that the severe forms in humans followed contamination by poultry, and not by cattle. In addition, more mutations were found in these people than in viruses circulating in poultry. They are thought to have originated in humans. One thing is certain: if new mutations appear that facilitate transmission between humans, it will be a considerable change. We must monitor these genetic developments very closely and in France we have research resources for this, from Anses, in Ploufragan (22), for example, or from Inrae.
We will be able to do better than for covid-19, even if we will not be perfect.
The world’s unpreparedness for the covid-19 pandemic, exactly five years ago, led to millions of deaths and cost trillions of euros. Are we better equipped today to face the next health crisis?
Even if we don’t know where the next pandemic will come from, we are better prepared than at the time of covid-19. We learned how to improve our means of surveillance, whether on humans, in the environment or on animals. Projects have been launched to identify mutations that allow viruses to pass from one species to another. There is also a whole section of innovation, with work to develop vaccines and treatments for pathogens, listed by the WHO, whose mortality potential would be significant in the event of an epidemic. With all of this, we will be able to do better, even if we won’t be perfect, that’s for sure. We still have to learn.
Is fighting against scientific disinformation, particularly on vaccines, seen as a priority in the face of the threat of a new pandemic?
Covid-19 has also taught us to think about vaccine hesitancy and projects have been launched on this subject. Furthermore, we are in the process of creating a group to work on how to counter disinformation in the context of an epidemic, what we call the “infodemic”.
A first case, in France, of the new variant of Mpox (formerly monkeypox) was detected in Brittany this month. Is there a high risk that this variant will spread?
This first case of “clade 1b”, in France, is not the first in Europe. Moderation is needed on its potential impact: the case identified in Sweden, in August 2024, did not generate an epidemic. As there is one, uncontrolled, in Central Africa, it is obvious that we will have cases here. To avoid them, it is very important that the countries of the North help countries with limited resources in the management of these epidemics.
-A new Mpox epidemic that spreads to the rest of the world, like that of 2022, is therefore not possible?
We will not wait until there is an epidemic in Europe to act. On the one hand, transmission occurs by contact, particularly sexually, which makes the fight easier than against a respiratory virus. We also have a vaccine, and a significant proportion of people at risk have already received an injection. And, when a case occurs, we can recommend that they not have close contact, and we can vaccinate those close to them, etc.
Climate change is facilitating the expansion of the tiger mosquito in mainland France. Are we at the mercy of outbreaks of the diseases it carries, like dengue, chikungunya and Zika?
We must never fall into resignation. Certainly, with global warming and globalization, the risk is increasing in mainland France, we are even starting to see cases of dengue fever. But we can always delay its arrival and fight. We have a vaccination strategy that is developing and it remains necessary to detect patients very quickly, to establish a perimeter, and to carry out mosquito control.
What other diseases do you have in your eye?
We are closely monitoring Oropouche fever, the number of cases of which has increased significantly over the past three years in the Amazon. We even had cases in Guyana. The virus is transmitted by midge bite and, most of the time, produces mildly symptomatic forms. But there remains a risk of encephalitis (inflammation of the brain) and transmission from mother to child during pregnancy, although there is currently no vaccine or treatment. We also remain vigilant about the increase in cases of chikungunya in Reunion. The Valneva laboratory has developed a vaccine (an opinion from the High Health Authority is awaited for its use). Finally, we always have an eye on potential epidemics of hemorrhagic fevers in sub-Saharan Africa, caused by the Ebola and Marburg viruses.
By focusing on new, booming diseases, are we forgetting others like AIDS? What is the latest progress recorded?
Regarding HIV, there are two major topics. On transmission, firstly, appropriation of new screening means is necessary by vulnerable populations. PrEP (preventive treatments), injectable every six months, also constitute a major advance, not yet in practice, but research projects have shown their effectiveness. With these tools, we could almost stop the transmission of HIV. Then, we must continue to work on the vaccine and on curing the disease.
The concept of “One Health” is one of the keystones of the research work coordinated by the ANRS MIE. How can human health, animal health and the environment be so interdependent and generate health crises?
There is a fairly telling historical example with the Nipah virus, in Malaysia. In this country, pig farming has expanded significantly, reaching the habitats of bats, which carry this virus. This is how the pigs became infected. Then, in large markets, pigs infected others until they reached humans. H5N1 and Oropouche are also other examples for which research resources are deployed to sequence viruses in animals and humans and explore their environment in order to see what is happening there.
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