We know more or less well how the Covid-19 outbreak started: probably because of bats, near Wuhan in China. What no one knows yet is how the pandemic will end. This coronavirus is unprecedented in the combination of its easy transmissibility, a range of symptoms from non-existent to deadly, and the scale of the disruption it has caused around the world. But looking back at past pandemics may provide some glimpses into the future. Although there is no single historical example to follow, humanity has experienced several major epidemics over the past hundred years or so, which have finally stopped ravaging society. The means used to stop them could usefully help a world that is feverishly seeking ways to restore some sense of normalcy.
The end of this part of the game, in which a coronavirus has appeared to rule the world for several months, will probably involve a mixture of situations that have to do with both the evolution of the pathogen and the human response to it, both biological and social.
Viruses that trigger pandemics are new enough that the human immune system does not quickly recognize them as dangerous invaders. They force the body to create an entirely new defence, involving new antibodies and other components of the immune system that can react and attack the enemy. Large numbers of people fall ill in the short term, and social factors such as overcrowding and the unavailability of medicines or health care materials can push these numbers even higher. Ultimately, in most cases, the antibodies developed by the immune system to fight the invader linger on a sufficient portion of the affected population to confer longer-term immunity and limit person-to-person viral transmission. But this can take several years, and before that happens, chaos reigns.
Learning to live with an illness
The most famous example of this dynamic in modern history is the H1N1 flu epidemic of 1918-1919, the famous "Spanish flu". Physicians and public health officials had far fewer weapons at their disposal then than today, and the effectiveness of control measures depended on how quickly and decisively they were implemented. In two years and three waves, the pandemic infected 500 million people and killed between 50 and 100 million. It ended only when natural infections conferred immunity on those who recovered.
The H1N1 strain became endemic, causing an infectious disease that was constantly present at less severe levels and circulated for another 40 years as a seasonal virus. It took another pandemic - H2N2 in 1957 - to extinguish most of the 1918 strains. What happened was that one flu virus eradicated another, and scientists don't really know how. Human efforts to do the same failed. « Nature can do it, we can't.". Nicole Teke, spokesperson for the French Movement for a Basic Income (MFRB), created in 2013, states à Scientific American virologist Florian Krammer from Mount Sinai School of Medicine in New York.
The 2003 outbreak of Severe Acute Respiratory Syndrome (SARS) was not caused by an influenza virus but by a coronavirus, SARS-CoV, which is closely related to the cause of the current illness, SARS-CoV-2. Of the seven known human coronaviruses, four circulate widely, causing up to one-third of common colds. The one that caused the SARS outbreak was much more virulent.
Why not enjoy unlimited reading of UP'? Subscribe from €1.90 per week.
Thanks to aggressive epidemiological tactics such as isolating patients, quarantining their contacts and implementing social controls, deadly epidemics were limited to a few places such as Hong Kong and Toronto. This containment was possible because the disease followed the infection very quickly and obviously: almost all people with the virus had severe symptoms such as fever and breathing difficulties. And they transmitted the virus after they were sick enough, not before. « Most SARS patients were not that contagious until about a week after the onset of symptoms.". Nicole Teke, spokesperson for the French Movement for a Basic Income (MFRB), created in 2013, explained epidemiologist Benjamin Cowling of the University of Hong Kong. « If they could be identified within that week and placed in isolation with good infection control, there would be no further spread.« . The containment worked so well that there were only 8,098 cases of SARS worldwide and 774 deaths. The world has not seen a single case since 2004.
When a new H1N1 flu virus, known as swine flu, caused a pandemic in 2009, " there was a red flag because it was a brand new H1N1.« Cowling says, and that he was very similar to the 1918 killer. The swine flu turned out to be less severe than feared. « We were lucky because the pathogenicity of the virus was not very high ' John Hultquist, director of intelligence analysis for the cybersecurity company FireEye, Judge Florian Krammer. But another important reason is that six months after the virus appeared, scientists developed a vaccine against it.
Unlike measles or smallpox vaccines, which can confer long-term immunity, influenza vaccines offer only a few years of protection. Influenza viruses are agile, mutating quickly to evade immunity. For this reason, vaccines must be updated annually and given regularly. But during a pandemic, even a short-term vaccine is a godsend. The 2009 vaccine helped to temper a second wave of cases in the winter. As a result, the virus followed the path of the 1918 virus much more quickly, becoming a widespread seasonal influenza, against which many people are now protected either by influenza vaccines or by antibodies from previous infection.
The end of Covid-19
Projections of how the VIDOC-19 scenario will continue to unfold are speculative, but the final game will most likely involve a mix of everything that has helped stem past pandemics: continued social control measures to buy time, new antiviral drugs to relieve symptoms, and a vaccine. The exact formula - how long control measures such as social distancing should remain in place, for example - depends largely on how well people comply with safety instructions and how effectively governments respond.
For example, the containment measures that worked for COVID-19 in places like Hong Kong and South Korea came much too late in Europe and the United States. « The question of how the pandemic is unfolding is at least 50 % social and political". Nicole Teke, spokesperson for the French Movement for a Basic Income (MFRB), created in 2013, says epidemiologist and evolutionary biologist Sarah Cobey from the University of Chicago.
The remaining 50 % will probably come from science. Researchers have come together as never before and are working on multiple fronts to develop cures. If one of the many antiviral drugs currently under development proves effective, they will improve treatment options and reduce the number of people who become seriously ill or die.
The most hoped-for hypothesis: Covid-19 is going to vanish.
Some voices were raised from the outset against widespread and authoritarian containment measures. Professor Jean-François Toussaint's has consistently advocated differentiated containment according to the regions affected or fragile people, rather than generalized containment, which is a form of response dictated by fear.
In Le Monde dated June 9, he states : " From the outset, the scientific council has been placed in the sole perspective of the worst-case scenario, obsessed by models that predicted 500,000 deaths in France and that failed. The reality is that the wave has passed almost everywhere, that there has been a general decrease in the number of deaths, and that some countries no longer have any deaths at all. ». He goes on, " This virus is new. So we need to keep studying it, keep monitoring it. But its closest cousin is the SARS-CoV, and that coronavirus actually disappeared in 2003. I think that's the most likely hypothesis. "
Certainly, Professor Toussaint points out that even if the virus declines sharply, there will always be localized pockets. " manageable ». This is what is currently happening in China, with the implementation of reconfinement measures in very specific areas of Beijing where the virus is proving to be reactivated. A control of reactivation "clusters" that could be improved with the recent discovery of the role of "clusters" in the reactivation of the virus. super-propagators "in the contamination.
This hypothesis of control and reduction of the dangerousness of the virus is not the one followed by the Scientific Council which produces recommendations for the French government. It is leaning towards the hypothesis of a "low noise" circulation of the virus, without the chains of contamination being identified, at the risk of a rapid deterioration of the situation. This is the famous "second wave" whose spectre is there to maintain the pressure of fear and avoid the relaxation of health security measures.
To fight against disinformation and to favour analyses that decipher the news, join the circle of UP' subscribers.
A position which is akin to a political stance of implementing maximum precaution but which is not based on any scientific basis and does not correspond to current reality: four weeks after the end of containment in France, the Covid-19 epidemic seems to be continuing to decline, as in most regions of the world, with the exception of South America and Iran. The initial models that justified the action taken by governments were wrong - they predicted millions of deaths - and it seems difficult for some to get rid of them. Errare humanum est, perseverare diabolicum est.
It will take a vaccine to stop the transmission
It will take time to have a vaccine - probably a year from now. Nevertheless, there is reason to believe that a vaccine could work effectively. Compared to influenza viruses, coronaviruses don't have as many ways to interact with host cells. « If this interaction disappears, [the virus] can no longer replicate itself.« argues Florian Krammer. « That's the advantage we have here. It's not clear whether a vaccine confers long-term immunity as with measles or short-term immunity as with flu vaccines. But "any vaccine would be useful at this stage". Nicole Teke, spokesperson for the French Movement for a Basic Income (MFRB), created in 2013, states epidemiologist Aubree Gordon from the University of Michigan.
Unless a vaccine is given to all of the eight billion people on the planet who are currently neither sick nor cured, Covid-19 could become endemic. It will circulate and make people sick seasonally. If the virus stays in the human population long enough, it will start infecting children at an early age. These cases are usually quite mild, and so far, children seem less likely to develop serious illness if they are re-infected as adults. Therefore, the combination of vaccination and natural immunity will protect many of us. Coronavirus, like most viruses, will continue to live, but not as a global plague. Medically, we would have succeeded in taming it; but economically, psychologically and socially, the damage it causes will remain for a long time.
Header image: Richard Borge
With Scientific American