World in lockdown.

Around a fifth of the global population is in lockdown as covid-19 cases continue to rise, reports Jessica Hamzelou.

THE covid-19 pandemic is speeding up, the World Health Organization's director general has warned. As New Scientist went to press, 382,000 cases of the disease had been confirmed, although the actual number is likely to be much higher. More than 16,500 people have died.

“It took 67 days from the first reported case to reach the first 100,000 cases, 11 days for the second 100,000 cases and just four days for the third 100,000 cases,” Tedros Adhanom Ghebreyesus told journalists at a press briefing on Monday. “The virus is accelerating.”

On the same day, the UK government announced that everyone should stay at home, leaving the house only for basic necessities like food and medicine, to meet the medical needs of themselves or others, to travel to and from work if necessary and for one form of exercise per day. For at least the next three weeks, non-essential shops and venues will be closed and public gatherings of more than two people are banned. Those who don't comply face fines or dispersal by the police.

While Hubei province in China, where the outbreak started, plans to lift its travel restrictions, a similar lockdown came into effect in New York City on Sunday, when New York state accounted for half of the confirmed US covid-19 cases.

On Monday, South Africa's president, Cyril Ramaphosa, announced a 21-day national lockdown, set to begin on 26 March. On Tuesday, India reported 519 confirmed cases and 10 deaths. It has imposed a three-week lockdown on its 1.3 billion people.

Strict measures do seem to slow the spread of infection. A team in Singapore has used modelling to show that measures including isolating infected people and quarantining their relatives, closing schools and encouraging people to work from home would significantly reduce the number of infections. Assuming a starting point of 100 infected people, these measures would cut the number of cases by 99.3 per cent over an 80-day period in Singapore, the model found (The Lancet Infectious Diseases, doi.org/dqfh).

These measures could ease the strain on health services by slowing the outbreak, but the only way to truly control outbreaks is to test suspected cases, properly isolate them and trace all of the people they have come into contact with, the WHO's director general has repeatedly said.

Despite this, the approach to testing suspected cases varies wildly between countries. The UK is still only testing people who are hospitalised. It is reported that just nine of the 2700 passengers that disembarked the Princess Ruby cruise ship in Sydney on 8 March were tested, despite reports of 158 passengers feeling unwell while onboard. Since then, 133 of the passengers have tested positive for covid-19, and one person has died.

In the meantime, researchers are starting to learn more about the virus, how it infects us and who is vulnerable. Until 22 January, only one case of infection had been reported in children in mainland China. A 24 February report covering 44,672 cases found that children under the age of 10 made up less than 1 per cent of cases and no deaths (JAMA, doi.org/ggmq43).

Since then, more cases of children hospitalised with the infection have come to light. Based on reports from a handful of hospitals in China, one team estimates that, by 22 January, around 1105 children were receiving hospital treatment for covid-19 in the city of Wuhan alone (medRxiv, doi.org/dqfg). If there were this many severe cases, tens of thousands of children were likely to have had mild cases, the authors say.

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