As scientists and authorities try to curb the coronavirus epidemic, one question remains: is it possible to totally eradicate a disease like Covid-19? For the moment, only smallpox and rinderpest have been able to disappear thanks to vaccination campaigns, as the conditions to be met are numerous.

Will we be able to overcome the Covid-19? While some health professionals try to relativize the ambient “alarmism” around a possible “second wave”, a question remains: will we be able to stop the epidemic and eradicate the new coronavirus? “In our current situation, it is very unlikely that we will be able (…) to eliminate this virus”, judged on July 10 in Geneva the executive director of the World Health Organization (WHO), Michael Ryan, during a press conference *. There are some very particular environments where this can happen, island states and other places, but even these risk re-imports. [du virus]”, analyzed the epidemiologist.

We saw countries that had managed to reach zero [cas] or almost zero, re-import the virus from outside. So there is always a risk.Michael Ryan, WHO Executive DirectorWHO press conference in Geneva, July 10, 2020

Jean-Claude Manuguerra seems to share this view. For the director of the Emergency Biological Intervention Cell at the Institut Pasteur, interviewed on RMC on July 21, “we will not be able to completely eliminate the virus”, unless a particularly effective vaccination campaign is undertaken. So even beyond Covid-19, is it simply possible to permanently eradicate an infectious disease? Franceinfo gives you some answers.

First, there is a question of definition. Getting rid of an infectious disease can mean “two things”, Jean-Claude Manuguerra explains to franceinfo: either “elimination of the disease in humans “, with or without geographical restriction, either “the eradication of the virus on Earth so that it no longer circulates at all”, including in potentially affected animal species.

For this, several conditions must be met. In the first place, “The virus must no longer have an animal or environmental reservoir, otherwise reintroductions could happen at any time. It is for example illusory to remove all the birds to make the flu disappear”, says this expert. “We can therefore eliminate the disease in humans, but not eradicate it on the planet.”

Other necessary condition: “The virus must be genetically stable. If a virus mutates all the time, we will not be able to have immunity for the entire population. (…) The fewer variants of the virus, the better we can fight against him”, indicates the researcher. The latter recalls that, each year, the vaccine against the seasonal flu is updated according to the nature of the viral strains in circulation.

Fighting an infectious disease also requires the ability to identify and trace infections. According to the WHO *, only 5 to 10% of the 1.7 billion people infected with Koch’s bacillus (the bacterium responsible for tuberculosis) are led to develop the disease, making its eradication a priori impossible in the current state. knowledge. And it is precisely there that is a crucial point in the fight against a virus. To eliminate it, “you need a very effective vaccine”, “inexpensive and easy to administer to practically all of the world’s population “, or to the animals concerned, says the virologist.

Should we still have the means to do it, emphasizes Jean-Claude Manuguerra. “We eliminated rabies from French territory by vaccinating domestic animals and also foxes, man being a dead end [il n’y a pas de transmission interhumaine du virus]. But in the rest of the world, rabies causes 59,000 deaths per year [principalement en Asie et en Afrique].” Ending this virus is proving difficult to do, analyzes Anne-Marie Moulin, emeritus research director at the CNRS. “Eradicating rabies would mean controlling all sectors, including lesser-known animals”, precise, circumspect, the philosopher and doctor.

So with so many conditions to be met, have we already eradicated infectious diseases? Yes, but in only two cases: smallpox and rinderpest. Still, the virus responsible for smallpox exists “at least in two laboratories”, indicates Anne-Marie Moulin, more specifically the Centers for Disease Control and Prevention in Atlanta (United States) and the National Center for Virology and Biotechnology Research in Novosibirsk (Russia), as reported Le Figaro. “One of the questions is whether we should not destroy the virus permanently in the laboratory, even if we know its complete sequence and there are other viruses of the same family in nature”, nuance the research director.

A real scourge that would have killed 300 million people in the twentieth century alone, recalls the BBC *, smallpox (also called “smallpox”) was declared as eradicated by the WHO in 1980 * after a major vaccination campaign and surveillance program (at a cost of $ 300 million *), launched thirteen years earlier.

For its part, rinderpest only affected, as its name suggests, cattle, and had major economic consequences for the affected regions, particularly in sub-Saharan Africa. It was declared eradicated in 2011 *, again after a vaccination campaign.

While no other infectious disease has officially disappeared, several appear to be close to extinction. The International Task Force for Disease Eradication (ITFDE), hosted by the center of former US President Jimmy Carter, identified in 2008 * (PDF) seven infectious diseases to target as a priority: measles, mumps, rubella, poliomyelitis (or polio), dracunculiasis, lymphatic filariasis as well as tæniasis.

But in 2020, these infectious diseases are still circulating. International programs are behind schedule, such as the polio virus, two out of three types of which have now been eradicated. The WHO even fears the appearance of 200,000 new cases per year in the next ten years if its elimination fails. As for dracunculiasis, the scientific journal The Lancet* reports that its planned eradication date has been pushed back several times because it could not be met.

To explain such difficulties, Jean-Claude Manuguerra points out “pockets of resistance, especially in developed countries, due to a lack of scientific culture and the spread of false news against the use of vaccines, in addition to religious opposition.” In 2019, in the face of anti-vaccine movements, the German Federal Parliament had made the vaccination of children against measles compulsory.

There are also questions of “the state [inégal] country health systems “ and some “political stability”. “These massive eradications, which require a lot of money and goodwill, require peace”, underlines Anne-Marie Moulin, who recalls that, in the 1960s, the success of the eradication of smallpox in Afghanistan by American teams could have been quite different in the context of the civil war that followed.

Should we therefore resign ourselves? For the historian Patrice Bourdelais, from the Ecole des Hautes Etudes en Sciences Sociales (EHESS), author of a column in The world on the character “unrealistic” of these eradications, “In the 1970s there was a kind of blind faith in the progress of science and medicine. We imagined eradicating all infectious diseases one by one.”

Even if we eradicate the diseases that exist, there are always diseases that reappear. This became clear as emerging or re-emerging diseases circulated, such as AIDS, Ebola, Mers or SARS.Patrice Bourdelaisto franceinfo

What about Covid-19? For now, there are only unfinished vaccine projects, two of which appear to be showing conclusive results. Impossible, therefore, to completely eradicate the virus even if it is possible to curb the epidemic. Especially since, as Jean-Claude Manuguerra reminds us, the Sars-CoV-2 crisis had a starting point “zoonotique” (with animal-to-human transmission) and non-human. Its exact origin is still unclear. “In any case, we will not eradicate [tous] coronaviruses. There are probably thousands “, adds the researcher.

This is what prompted 18 Canadian health experts to write an open letter to Prime Minister Justin Trudeau, claiming that “preventing or containing every case of Covid-19 is simply no longer viable at this stage of the pandemic “ and has social costs. According to the British data site Our World in Data *, on July 28, Canada had 699 new cases of Covid-19. “We have to accept that Covid-19 will be part of our daily life for some time and find ways to deal with this situation”, write the specialists.

For Jean-Claude Manuguerra, it would indeed be “too complicated (…) to eradicate the virus by strictly sanitary measures” in the absence of vaccine. “You have to live with it, but still protect yourself”, says the virologist, who recalls that, for HIV, there too, “barrier measures” were put in place when the epidemic occurred, such as wearing a condom. An observation that Patrice Bourdelais completes: “The longer this epidemic will last, the more our behavior will change. (…) People may realize that wearing a mask is not that embarrassing and is very effective, not only against Covid-19. ”

* These links refer to pages in English.