COVID-19: Top science stories of the week, including new diabetes link and the latest Beijing outbreak

China releases genome of latest viral outbreak in Beijing

China has released genome sequencing data from samples taken in Beijing, amid the latest outbreak in the capital.

Virus genome sequencing is a vital and rapidly-developing tool in the diagnosis of COVID-19 and in understanding the spread and control of the new coronavirus as it moves around the globe.

The latest genome sequencing – which has been shared with the World Health Organization (WHO) and the Global Influenza Data Initiative (GISAID) – has identified a European strain of the virus, according to Chinese officials. But the WHO said that further investigation was needed to understand the origin of the latest outbreak.

Evidence suggests coronavirus might trigger diabetes

Diabetes is a known risk factor for developing severe COVID-19 and people with the condition are more likely to die. Now, some researchers are also pursuing the idea that diabetes doesn’t just make people more vulnerable to the coronavirus, but that the virus might also trigger diabetes in some.

Early evidence from tissue studies and some people with COVID-19 shows that the new coronavirus damages insulin-producing cells, which are important for regulating blood sugar levels.

A handful of COVID-19 patients have spontaneously developed diabetes and dozens more have arrived in hospital with extremely high levels of blood sugar and ketones, which are produced from fatty deposits in the liver. When the body doesn’t make enough insulin to break down sugar, it uses ketones as an alternative source of fuel.

New findings from experiments on miniature lab-grown pancreases also suggest that the virus might trigger diabetes by damaging insulin-producing cells.

However, in order to prove a causal link between the virus and the onset of diabetes, researchers will need to conduct well-constructed epidemiological cohort studies as well as further lab experiments.

Young people shielded from infection by close contacts

People under the age of 20 are much less likely than their elders to catch the new coronavirus from an infected household member, according to new research led by scientists at the University of Florida and the Center for Disease Control and Prevention in China.

The team analysed viral transmission between infected people in the city of Guangzhou in China and those who’d had close contact with them. After public-health officials enforced isolation of infected individuals and quarantine of their contacts, people under the age of 20 had a 5.2% risk of being infected by a member of their household, compared with a 14.8% risk for people aged 20–59 and an 18.4% risk for people aged 60 and above.

The researchers also found that people with COVID-19 were at least as infectious before their symptoms started as after, adding to the evidence of asymptomatic and pre-symptomatic viral spread.

Majority of infected people never show classic symptoms

More than two thirds of people infected with coronavirus in Lombardy – the epicentre of the outbreak in Italy – did not display symptoms, according to new unpublished research.

Researchers studied people in Lombardy who had had close contact with an infected person. Roughly half of these 5,484 contacts became infected themselves. Of those, 31% developed respiratory symptoms or a fever and only 26% of those under the age of 60 did so.

As a person’s age increased, so did their odds of experiencing symptoms and becoming ill enough to require intensive care, or to die.

Possible higher risk for blood group A

Genome-wide association studies are a relatively new way for scientists to identify genes involved in human disease. This method searches the complete set of genes – known as the genome – for small variations that occur more frequently in people with a particular disease than in people without the disease.

A genomewide association study involving 1,980 patients with Covid-19 at hospitals in the Italian and Spanish epicentres of the European pandemic, reveals that people with blood type A have an elevated risk compared to non-type A individuals.]