COPENHAGEN, Denmark (AFP) — A senior World Health Organization official on Thursday urged national authorities to make a priority of understanding the long-term consequences of coronavirus infections as some people show worrying symptoms months later.

“It’s a clear priority for WHO, and of the utmost importance. It should be for every health authority,” Hans Kluge, regional director for WHO Europe, told a press conference.

While some studies are beginning to shed light on the illness, it is still unclear why some patients with COVID-19 continue to show symptoms for months, including tiredness, brain fog, and cardiac and neurological disorders.

“The burden is real and it is significant. About one in 10 COVID-19 sufferers remain unwell after 12 weeks, and many for much longer,” Kluge said.

Noting that reports of long-term symptoms came soon after the disease was first discovered, he said that some patients were “met with disbelief or lack of understanding.”

Kluge stressed that those patients “need to be heard if we are to understand the long-term consequences and recovery from COVID-19”.

WHO Europe called on European countries and institutions to “come together as part of an integrated research agenda,” harmonising data collection tools and study protocols.

The regional director also said he would bring together the 53 member countries of the WHO’s European region, including several countries in Central Asia, “to set out a regional strategy”.

In early February, WHO organised the first virtual seminar devoted to so called “Long COVID,” in order to properly define it, give it a formal name and harmonise methods for studying it.