PARIS • An estimated 1.7 billion people - more than 20 per cent of the world's population - risk becoming severely infected with Covid-19 due to underlying health problems such as obesity and heart disease, an analysis showed yesterday.

The coronavirus, which has killed around 440,000 people globally, adversely affects those suffering from co-morbidities.

A team of experts from the London School of Hygiene and Tropical Medicine analysed global data sets of illnesses including diabetes, lung disease and HIV, and used these to estimate how many people are at heightened risk of serious Covid-19 infection.

They found that one in five people have at least one underlying health problem putting them in greater danger.

While not all of those would go on to develop severe Covid-19 symptoms if infected, the study said 4 per cent of the global population - or around 350 million - would likely get sick enough to require hospital treatment.

"As countries move out of lockdown, governments are looking for ways to protect the most vulnerable from a virus that is still circulating," said Dr Andrew Clark from the London School of Hygiene and Tropical Medicine and a contributor to the study.

"This might involve advising people with underlying conditions to adopt social distancing measures appropriate to their level of risk."

Dr Clark said that the findings could help governments make decisions on who should receive a Covid-19 vaccine first when one becomes available.

Consistent with other studies, the authors found that seniors are in greater danger of becoming seriously unwell from the virus.

Less than 5 per cent of people aged under 20 have an underlying risk factor, compared with two-thirds of those aged over 70.

Countries with younger populations have fewer people with at least one underlying condition but risks vary globally, according to the study.

For example, small island states like Fiji and Mauritius have among the world's highest rates of diabetes, a known Covid-19 risk factor.

And countries with the highest prevalence of HIV/Aids also need to be vigilant, said authors of the research, which is published in The Lancet.

In Europe, more than 30 per cent of people have one or more health conditions, it showed.

Writing in a linked comment, Ms Nina Schwalbe from Columbia University Mailman School of Public Health said the study showed "it is time to evolve from a one-size-fits-all approach to one that centres on those most at risk".

AGENCE FRANCE-PRESSE