One assumption, made by doctors in Italy, is that the coronavirus may weaken as it spreads. By viral mutation, Sars-Cov-2 could lose its potency and become milder or less infectious. But coronaviruses have proven to be a remarkably stable type of virus. There is no evidence to support this type of mutation occurring in a few years, let alone weeks. Rather than viral mutations, the improvement in survival rates in Italy is probably linked to better clinical management of Covid-19, as doctors learn to treat patients in hospital more effectively.
Another point of view is that the number of people susceptible to this virus is smaller than expected, either because a large part of the population has already been exposed to it, or because it has developed cross-immunity against other similar viruses. This scenario also seems unlikely. The first serological tests estimated that only 17% of Londoners and 5% of the British population had been exposed to the virus at the end of May. This means that there is still a large percentage of the population who have not yet had a chance to develop immunity, an image that corresponds to serological studies from France, Spain and Sweden, which gave similar results.
But the picture could be more complex. A recent study found that people who had never been exposed to Sars-Cov-2 still had T cells that respond to the virus, another key component of the body’s immune response. The study authors suggested that previous exposure to common cold coronaviruses could mean that the body is able to detect proteins from the Sars-Cov-2 virus. While this finding may be promising, there is still no evidence that antibodies or T cell reactivity would lead to the development of immunity against Sars-Cov-2.
A third approach, which has been deliberately adopted in Sweden, is to let the virus run its course and spread through the population. This treats Covid-19 much like the flu virus; until a vaccine becomes available or enough people are exposed for collective immunity to develop, the virus will be unstoppable.
But the cost of allowing the virus to spread through the population until it develops collective immunity is that many people will fall ill or die as a result of the capture of Covid-19. And without confirmation of the duration of immunity, this approach offers no certainty as to the possibility of re-infecting people after a few months or years – leading to a second wave of infections.
In my opinion, we can avoid a second wave if governments aggressively contain the virus by testing, tracing and isolating carriers, and encouraging good hygiene, such as hand washing and environmental disinfection, supported by physical distance where it is needed. The goal is to reduce the number of cases to a low level so that transmission is limited to discrete and containable epidemics with the ultimate goal of elimination.
Think about that like a series of small, constantly emerging fires that need to be put out quickly before it turns into an uncontrollable fire. South Korea and Germany have effectively followed this approach, deploy mass testing and tracing strategies, isolate carriers of the virus and set up surveillance systems to map its spread.
But the focus on deaths from a second wave may miss the true toll of the virus: the long-term damage it can cause to the lungs, heart, kidneys, brain and even blood vessels among those who recover. This emerges as one of the horrors of Covid-19. We often forget that Covid-19 is a completely new virus, completely different from the flu, and that it could have longer-term health effects that will only be identified in months or years.
If coronavirus is the polio of our generations, we could look to the approach taken by Pacific governments. New Zealand has eliminated the coronavirus and Australia is moving closer to that goal. With border controls in place, people living in these countries can resume a normal life. Sports matches are taking place in New Zealand, schools have reopened, weddings are booked and people can see parents safely.
The successes of New Zealand and Australia could force other countries to rethink their own strategies and the possibility of eliminating the virus within their borders. Instead of living with a constant threat from Covid-19, people could start asking their own governments – why not try to get rid of it completely?
• Professor Devi Sridhar is President of Global Public Health at the University of Edinburgh