As soon as a new coronavirus was identified in China at the end of last year, the world’s scientists set about investigating the threat it posed.
Each week we bring you a round-up of the progress they’ve made in understanding the spread of Covid-19 – and developing the vaccines, treatments and preventative measures that will bring it under control.
Immunity puzzle
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If epidemiologists could choose to uncover just one key insight about the Covid-19 outbreak, it would probably be a reliable count of how many people have already had the virus.
This figure would help governments “determine when it is safe to lift the lockdowns that have curtailed their citizens’ personal lives and had a devastating effect on businesses and the global economy”, the Financial Times reports.
A flurry of research papers published this week suggest the figure may vary sharply from place to place:
- in a study of 3,000 people, 21.2% of New York City residents and 13.9% of people across New York State tested positive for Covid-19 antibodies, suggesting they have had the virus
- in Los Angeles, tests carried out on a representative sample of 846 people found that only 4% of people had antibodies
- in the Netherlands, only 3% of blood donors are testing positive for Covid-19 antibodies. The sample size hasn’t been made public, but Dutch authorities have been aiming to test 10,000 blood samples a week since the end of March.
The findings indicate that even areas with high levels of infection are unlikely to have reached the point of herd immunity. “You would have hoped for 45% or even 60% positive,” Mark Perkins of the World Health Organization (WHO) told the American Association for the Advancement of Science.
“That would mean that there is lots of silent transmission, and a lot of immunity in the population. It now looks like, sadly, that’s not true.”
Australia’s ABC News reports that in Sweden – where mathematical modelling suggests that about a quarter of the population of Stockholm will have been infected by 1 May – epidemiologist Anders Wallensten has warned that being infected with the virus may not protect people against contracting it again.
“We don’t know that much about immunity yet,” he told a press conference. “We will know more as more people are tested for antibodies, but also if more accounts of reinfection are reported.”
This message has been echoed by other researchers.
“There’s a risk of really serious misinterpretation here,” William Hanage, associate professor of epidemiology at Harvard University, told NBC News. “But the most basic conclusion – that quite a large number of people may have been infected and are not turning up in the official case counts – that’s extremely plausible and something we have been suspecting all along.”
Over the next year, the UK plans to test a representative sample of 300,000 people for coronavirus infection and immunity.
Blood plasma treatment
Despite Donald Trump’s enthusiasm for injecting disinfectant into coronavirus patients, doctors are focusing their efforts on treatments using blood plasma. Hospitals in both the UK and the US are giving blood donated by people who have recovered from Covid-19 to patients seriously ill with the virus.
“The hope is that the antibodies they have built up will help to clear the virus in others,” the BBC reports. A trial is already under way in New York, where “hundreds and hundreds of donors” have come forward to help.
“We’re hearing interesting positive case reports,” Dr Michael Joyner, who is leading the project, told MarketWatch. However, he warned, “nobody tells you about your bad cases”.
Results from the study will provide more comprehensive information about the success rate.
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A Cornell University study has suggested that one way of lifting the lockdown while minimising the risk of infections would be for people to limit themselves to contact with a small group of people but no one else.
“While social distancing measures clearly do flatten the curve,” the paper concluded, “strategic reduction of contact can strongly increase their efficiency, introducing the possibility of allowing some social contact while keeping risks low.
“Limiting interaction to a few repeated contacts emerges as the most effective strategy,” the authors say.
