Three years ago, the Covid-19 upset the planet. The pandemic is not over and researchers warn that other epidemics are to be expected, drawing lessons from the crisis it has generated to better prepare for them. “We are not yet” at the end of the epidemic, warned the World Health Organization (WHO) in early December.
While at least 90% of the world’s population has some form of immunity, “gaps in surveillance, testing, sequencing and vaccination continue to create the perfect conditions for the emergence of a concerning new variant that could cause significant mortality, ”warned its director general Tedros Adhanom Ghebreyesus.
From pandemic to endemic virus
The WHO declares the end of a pandemic. “It is always an extremely important moment, often subject to controversy”, noted Philippe Sansonetti, microbiologist, during a symposium on Wednesday at the Institut Pasteur, judging that the organization was probably not ready to “whistle the end” of the pandemic.
What experts anticipate is a gradual transformation of the pandemic into an endemic virus, continuing to circulate and causing regular resurgences of the disease. This is the case today with measles or the seasonal flu.
The Covid and its “bad cases”
The SARS (severe acute respiratory syndrome) epidemic, which broke out worldwide in 2003 and claimed almost 800 lives, was stemmed by isolation and quarantine measures. A virus, smallpox, was already declared “eradicated” in 1980 thanks to a WHO vaccination campaign. But this scenario remains extremely rare.
“To eradicate a virus, it is necessary that the disease is clinically visible, that there is no animal reservoir, and to have a very effective vaccine, which protects for life. Covid-19 ticks all the wrong boxes,” said Philippe Sansonetti. Some of the carriers of Covid-19 are indeed asymptomatic, which affects isolation measures. And, unlike smallpox, the virus is transmitted to animals and could continue to circulate among them and reinfect humans. Finally, vaccines provide good protection against severe forms of the disease but little against reinfections, and booster doses are still necessary.
Humans promote the transmission of viruses
For Etienne Simon-Lorière, Director of the Evolutionary Genomics Unit for RNA Viruses at the Institut Pasteur, “today we allow the virus to circulate far too much”: each time it infects a person, mutations can appear. and are likely to cause it to evolve into more or less severe forms. “Even if it would suit us all to believe that, we have no reason to think that he will become more sympathetic,” he warned.
In addition, other respiratory viruses could emerge: since the appearance of Sras, Mers, and Sars-Cov2, “a good dozen coronaviruses have been found in bats which could potentially infect [l’humain] “, noted Arnaud Fontanet, specialist in emerging diseases at the Institut Pasteur. About 60%/70% of emerging diseases are of zoonotic origin, that is, they are naturally transmitted from vertebrate animals to humans and vice versa. By occupying larger and larger areas of the globe, by travelling, by intensifying their interactions with animals, humans contribute to disrupting the ecosystem and favoring the transmission of viruses.
Anticipate rather than react
For Arnaud Fontanet, “much can and must be done at the start of an epidemic” to prepare for it. Thus, in 2020, Denmark decided on confinement very early, which allowed it to get out of it more quickly, he argued. Another imperative: “to have the capacity to develop very early tests”, at the start of an epidemic, so as to isolate patients very quickly. “Unfortunately, today we are still in the reaction, not in the anticipation”, regrets the researcher.
At the international level, the “one health” concept, which appeared in the early 2000s, which promotes a global approach to health issues with close links between human health, animal health and the environment, is new emphasis. A draft global agreement on the management of pandemics was also under discussion last week in Geneva, in the hope of avoiding the mistakes that marked the fight against Covid-19.