Zero. The Spanish government’s announcement on Monday of the first day without coronavirus death left a lasting impression. If it must be taken with caution, it symbolizes a strong trend in Europe, that of a drastic drop in the number of deaths. An inevitable fall in the curve which continues despite the deconfinement. Only the United Kingdom, which took drastic measures later, still experiences very high mortality.
"What is reassuring is that there is no rebound," notes Mircea Sofonea, lecturer in epidemiology and evolution of infectious diseases at the University of Montpellier. If it had taken place, it would have been visible last week. However, we did not observe it ”.
Good news for which it is difficult to find a single reason. "There is a conjunction of factors linked to the virus and to humans, but also to the environmental situation," summarizes Daniel Camus, of the Institut Pasteur in Lille. It is then a virtuous circle that begins: less virus, therefore fewer sick people, therefore fewer possibilities of circulation ”.
Physical distance maintained
With the widespread use of the mask, the first of the effects of slowing the number of deaths is the continued application of barrier gestures by Europeans. "People have kept their reflexes and have not yet resumed their former life in France," notes Antoine Flahault, epidemiologist and director of the Institute of Global Health at the University of Geneva. But in Switzerland or Austria where deconfinement is wider and where wearing a mask is not compulsory anywhere, we do not observe more rebounds of the epidemic.
"There is still everywhere in Europe the maintenance of restrictions, which will be lifted gradually," adds Mircea Sofonea. There is also special attention paid to vulnerable and at risk people. This vigilance did not exist in recent months. The last aspect is the maintenance of the prohibitions on large gatherings, which are very important triggers for a restart of the epidemic. For the moment, the virus is circulating, but not enough to initiate an epidemic rebound. ”
Immunity on the rise
"There is also the acquisition of group immunity," explains Daniel Camus. First, the natural one that we develop throughout our lives, to which is added that of the population affected by the virus. Men also fight better against a virus or bacteria during periods when the duration of daily light is longer. ”
The fact remains that studies have not yet settled the question of the threshold at which the population would be protected from the epidemic. "This is the most complex hypothesis, because we are talking about cross immunity or lower level than initially envisaged because of the heterogeneity of the spread of the virus, estimates Antoine Flahault. But there are still many unknowns on this subject. "
The seasonal effect
"It seems more and more likely that this factor plays a role." For Antoine Flahault, the seasonal brake, with the arrival in Europe of hot and dry weather, remains the main element of the fall in the spread of the virus. "He is known for the flu and many other respiratory viruses," said the doctor. It is currently observed in temperate zones of the northern hemisphere that the Covid-19 epidemic is declining. While it is exactly the opposite that occurs in countries with temperate climates of the southern hemisphere. Southern Brazil, Chile, Argentina and South Africa are experiencing fairly strong epidemic outbreaks as they enter their winter and have not experienced them in recent months. "
"The mild weather creates an appetite for outdoor activities, especially after weeks of confinement," continues Mircea Sofonea. By leaving closed and poorly ventilated environments, people actually move away from conditions favorable to propagation. ” Could summer be a respite? "The return of winter, during which the virus will regain more favorable conditions and humans will lose immune defenses, may give the opportunity for a resumption of the epidemic". The game is not yet won against the Covid-19.