Coronavirus: the week explained

Welcome to this week’s roundup of developments from the coronavirus pandemic. As lockdowns continue to ease in countries around the world, scientists have been reflecting on why some groups have been harder hit than others, and which strategies have proved most successful in tackling the virus.

Soul searching in Sweden

The Swedish approach to tackling the coronavirus has been described as “light touch”, with shops, gyms and restaurants allowed to stay open, and the public simply asked to avoid non-essential travel or venturing out if unwell – measures in sharp contrast to the strict lockdowns of neighbouring countries including Norway and Denmark.

Now Sweden’s chief epidemiologist, Anders Tegnell, has said the country could have done better, agreeing on Swedish Radio that too many people had died from Covid-19 and adding that the country should have adopted a stance somewhere between the Swedish approach and that of other countries.

While Sweden’s per million death rate from Covid-19 is lower than those of the UK, Italy or Spain, it is far higher than that of Norway or of Denmark. And over the seven days to 2 June, it appears Sweden’s death rate per capita was the highest in the world.

But Tegnell has maintained that the government took the right steps. “Based on the knowledge we had then, we feel we made the appropriate decisions,” he told a Swedish newspaper.

Hydroxychloroquine remains in the limelight

The drug hydroxychloroquine, promoted by an enthusiastic Donald Trump, has once again been thrown into the spotlight after concerns were raised by the Guardian and scientists over the data on which an influential study into the drug was based.

The study, which was published in the journal the Lancet, drew on hospital data from around the world and concluded that hydroxychloroquine was associated with an increased risk of death or heart problems in people with Covid-19.

However, the Guardian revealed serious problems in how the data was collected, finding it was provided by a tiny US-based company called Surgisphere, and had clear errors. The Guardian also found Surgisphere’s employees did not appear to have a medical background; indeed one seems to be a science fiction writer.

Related: Hydroxychloroquine: how an unproven drug became Trump’s coronavirus 'miracle cure'

The Lancet has now retracted the study, while the World Health Organization, which had suspended its work on the drug because of the research, has said it will resume its clinical trials. The New England Journal of Medicine has also retracted a paper based on the Surgisphere data.

However, this week a randomised control trial – the “gold standard” for medical research – was published that found no sign that hydroxychloroquine is better than placebo in protecting individuals against infection with the coronavirus.

While experts have welcomed this study, they have said more research is needed since the trial was small, involving 821 participants, 107 of whom developed Covid-19. Further trials are under way, including one involving more than 40,000 healthcare workers.

Concerns over a second wave

A number of countries and regions are experiencing upticks in coronavirus cases after seeing infections fall, including Iran. The country has reported a rise in cases after easing lockdown restrictions in April.

Related: The first wave of Covid-19 is not over – but how might a second look?

The health minister, Saeed Namaki, said that if people did not stick to social distancing, the ramifications could be dire.

“My colleagues and the deputies of the ministry of health are working around the clock and travelling to one province every day to control this epidemic, but we are dealing with local issues and behaviours that could lead to the return of the peak of the disease,” he said.

Science Weekly podcast

In this week’s edition of Science Weekly, Ian Sample talks to Prof Carl Heneghan about the uncertainties in predicting future outbreaks of Covid-19 and what we can do to prevent them

Obesity warnings over Covid-19

Experts have warned that obesity increases the risk of death from Covid-19, and have said more needs to be done to help people reduce their weight, including by offering treatments such as gastric balloons.

According to Prof John Wilding, the president of the World Obesity Federation, obesity doubles the chances of death from Covid-19, while data from the European Centre for Disease Prevention and Control has revealed that almost three-quarters of patients critically ill with Covid-19 across a collection of European countries, including Italy, Spain and Sweden, are obese.

Doctors say among the reasons why obesity is a problem with Covid-19 is that it is harder to ventilate such patients, while severe obesity is known to affect the immune system.

Shaw Somers, a consultant bariatric surgeon, said: “With severe obesity, your immune system is working overtime. What we know from Covid is those who do badly have an exaggerated inflammatory response that comes on after seven to 10 days. Their immune system goes berserk and kills them. And we think that obesity just amplifies it and just makes it much worse.”

Experts say even being a few stone overweight could reduce the body’s resilience to illnesses, including Covid-19.