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TThe world is beginning to loosen the restrictions that have been put in place to limit the spread of Covid-19. Country, state and city leaders are discovering that they have little choice but to return to economic activity long before there is an effective vaccine or treatment for the disease. This means that secondary outbreaks are almost a certainty.
What is unclear is how devastating future increases in infection will be. If they are sporadic and kept under control, mortality rates will remain low and life may return to normal. If they are large, countries and regions may need to return to shutdown mode, spreading the economic damage of the pandemic.
Unfortunately, many of the factors that will determine what comes next are beyond anyone’s control.
That does not mean that countries are completely powerless over their destinies. Areas that open gradually and with widespread testing and contact tracking programs will be easier to detect and interrupt outbreaks. But nature will also play an important and unpredictable role, starting with the weather.
The coronavirus that causes Covid-19 could behave like the common coronaviruses that cause many mild respiratory infections. They spread more easily in colder, drier environments and have a harder time infecting people when the weather is hot and humid. (They are helped by the way people crowd inside during cold weather.) In the USA In the USA, these viruses generally peak in November and December and drop to a minimum from February to May.
Medical scientists have yet to determine to what extent seasonal trends apply to Covid-19. But any decrease in warm weather this year is likely to come late and not too much. After all, the disease did not appear in many parts of the world until late winter. While there is some evidence that this coronavirus does not care for heat, most transmissions have occurred indoors. And the existence of outbreaks in warmer countries (Thailand and Singapore, for example) and the virulence of Covid-19 suggest that dramatic summer suppression is unlikely.
However, seasonality can at least limit the size of any post-close bounce. New outbreaks in the Northern Hemisphere this summer could be smaller, and that would buy valuable time to advance testing, developing treatments, and strengthening health systems. On the other hand, it could also mean that the virus begins to spread more rapidly in the southern hemisphere and that subsequent outbreaks in the fall and winter will be especially severe in places where people do not take adequate precautions.
Theoretically, the coronavirus could also disappear, as viruses do, if populations acquire immunity and run out of people to infect. While most countries in the world have adopted social distancing or have aggressively invested in containment, Sweden has imposed only minor restrictions. Its objective is to reduce the economic impact of the pandemic. Running towards “collective immunity” is not an explicit policy objective, according to the country’s chief epidemiologist, but it is a useful threshold that he believes could be achieved in Stockholm in a matter of weeks.
The problem with this strategy, beyond its potentially high human cost, is that scientists know little about acquired immunity to Covid-19. Contracting a virus generally leads to future protection, as the body’s immune system remembers the mistake and is prepared with antibodies for the next fight. However, the duration and strength of this immunity varies depending on the disease, the intensity of the person’s infection, and other factors. There have been reports of people infected with the Covid virus twice, although this could reflect testing problems. But resistance to seasonal coronaviruses has been known to fade within a year. And while the antibodies to SARS, a cousin of Covid-19, have lasted longer, the SARS outbreak was extinguished before researchers had a chance to see if they generally prevent reinfection. Month-long studies of individuals with positive antibodies are needed to learn about acquired immunity to Covid-19.
Therefore, Sweden is taking a risk. And it’s not clear that it would be a good idea for any country to issue “immunity passports” for people who test positive for Covid-19 antibodies.
If immunity turns out to be easily gained and long-lasting, infection rates should decrease over time. If it is transitory and unreliable, the world could face annual or biennial outbreaks in the coming years. A model of Covid-19’s future transmission dynamics suggests that the size of outbreaks will vary dramatically depending on the seasonality of the virus and the duration of people’s immunity.
In the future, countries have experience and, having flattened the curve, more time to prepare. However, when the cold weather returns in the fall, they may face a new challenge: the simultaneous return of Covid-19 and the flu. This could sow confusion and tests of tension and hospital capacity. Robert Redfield, director of the US Centers for Disease Control and Prevention. In the US, he noted that a Covid-19 winter outbreak could be more troublesome even if it’s smaller than the one we have now.
It will help if more of the world’s population is vaccinated against the flu. In an average year, however, less than half of American adults do so.
Scientific advances could also steer Covid-19’s trajectory: the discovery of an effective treatment would greatly reduce suffering and strain in healthcare systems. The news Wednesday that Gilead Sciences Inc’s remdesivir accelerated recovery for some hospitalized patients in a placebo-controlled trial is welcome, even though it’s not the game changer that’s needed. And by fall, scientists should have data on laboratory-grown antibodies that could prevent and treat the disease. However, the treatments and vaccines that are now being worked on are targeting the version of the coronavirus that is currently spreading. Any significant mutation could undermine progress.
Faced with so many unknowns, countries and companies have no choice but to approach the reopening with all possible caution.
Also read: How China tries to prevent a second wave of infections
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