Coronavirus: the week explained

Welcome to our weekly roundup of developments in the coronavirus pandemic that continues to spread around the world. As the outbreak passed the 100-day mark and many countries extended their lockdowns, others moved to relax restrictions wary that cases may take off again.

Scientists shed light on immune response to coronavirus

On Monday, a team at Fudan University in Shanghai reported the first detailed analysis of the immune response in patients with coronavirus. Tests on the blood of 175 patients who had been discharged from hospitals in Shanghai revealed that neutralising antibodies – those that can wipe out the virus – usually arose 10 to 15 days after the onset of illness and targeted three different parts of the “spike” protein on the virus’s surface.

While older patients produced the highest levels of neutralising antibodies, many patients had low levels and 10 did not appear to generate them at all. If the findings hold up – the study has yet to be reviewed and published – they have widespread implications. The more robust immune response from older people suggests their blood plasma may work best in trials that are assessing whether convalescent plasma infusions can help seriously ill patients overcome the virus. But the findings may frustrate efforts to manufacture an accurate antibody test for the virus if many people have low or even non-existent levels of neutralising antibodies. This week it emerged that none of the antibody tests purchased by the UK government were good enough to roll out.

The work also has implications for “immunity passports”, which could allow people to return to normal life if blood tests showed they had developed immunity to the virus. Nearly 6% of the recovered patients had no neutralising antibodies, suggesting that other parts of the immune system had cleared the infection, without producing long-term immunity.

Not everyone agrees on wearing face masks

Whether or not to don a face mask in public became a matter of debate and confusion. After a review of new evidence, the World Health Organization maintained its view on Monday that while people who have cough, fever and difficulty breathing should wear a mask and seek medical help, there was no need for healthy people to wear face masks in public. The organisation conceded that people without symptoms can spread the virus, but only recommended healthy people wear face masks when they were caring for a coronavirus patient and in the same room. The masks can help prevent infections by catching large virus-laden droplets that are expelled from patients when they cough and sneeze, but David Heymann, who chairs the WHO’s risk committee, said face masks can give people a false sense of security if they do not combine an effective one with eye protection and adopt strict hand hygiene measures.

The UK has a similar stance to the WHO and does not recommend healthy people wear masks in public. But the US Centers for Disease Control and Prevention (CDC) not only advises people to wear face masks outside, but offers guidance on how to make “cloth face coverings” too. On Tuesday, US government scientists argued the case for face coverings after preliminary research showed people spray out thousands of tiny saliva droplets when they speak simple sentences such as “stay healthy”. Adriaan Bax at the US National Institutes of Health, who led the work, found a damp homemade cloth face mask “dramatically reduced droplet excretion”.

Some countries look towards easing lockdowns

Following in the footsteps of China, a number of countries announced plans to relax restrictions they had put in place to stop the spread of the virus. On Wednesday, China, lifted its 11-week lockdown in Wuhan where the outbreak began. The following day, the Czech Republic allowed bicycle shops and DIY, hobby and hardware stores to reopen. After the Easter break, Austria will let small shops, DIY stores and garden centres return to business, while Denmark plans to reopen kindergartens and primary schools. But with the virus still present and large numbers of people still vulnerable to infection, health officials are watching closely for cases to surge again. As Denmark’s prime minister, Metter Frederiksen, commented: “It’s like walking a tightrope.”

Related: Wuhan ends coronavirus lockdown – in pictures

The British prime minister, Boris Johnson, was admitted to intensive care for several days but returned to a ward on Thursday after he improved without needing mechanical ventilation. In his absence, the foreign secretary, Dominic Raab, scotched hopes for an early end to the UK lockdown and refused to be drawn on exit strategies until the country was beyond the peak of the epidemic. But discussions are underway in Whitehall where options range from a “youth first” policy that would allow young workers to return to their jobs, to a staggered sector-by-sector approach. To find out more about how to lift the lockdowns, listen to Adam Kucharski, associate professor at the London School of Hygiene and Tropical Medicine and author of The Rules of Contagion on the latest episode of our Science Weekly podcast.

New York’s epidemic was fuelled by travel back from Europe

Scientists have found that the coronavirus outbreak in New York was largely fuelled by US citizens bringing the infection back from Europe. President Trump imposed restrictions on travellers from China at the end of January but only blocked travel from most European countries in mid-March. Separate teams at the Icahn School of Medicine at Mount Sinai in New York City and New York University reached similar conclusions after studying the genetic code of viruses obtained from patients in the region. The scientists traced the origins of the outbreak by analysing patterns of mutations that accumulate in viruses as they spread. “The majority is clearly European,” Harm van Bakel, a geneticist from one of the teams, told the New York Times. The same approach was used last month to trace the coronavirus back to infected bats.

Related: How coronavirus spread across the globe - visualised

And finally…

As streets emptied out and factories closed their doors, scientists at the British Geological Survey noticed their sensitive earthquake-detecting seismometers had stopped twitching as much. Closer inspection of the charts revealed that the lockdown has changed how the Earth moves beneath our feet: there are fewer vibrations from human noise passing through the planet.

Related: Climate crisis: in coronavirus lockdown, nature bounces back – but for how long?

The fall in background noise, particularly around urban seismometers, has left scientists wondering if they might detect earthquakes that are smaller than normal, or at distances that are normally beyond their range. With lockdowns easing around the world, they do not have long to look. As Brian Baptie at the BGS conceded: “We may not get anything in the short term.”