LONDON - Thousands of COVID-19 patients continue to suffer serious, debilitating and lingering symptoms many months after their initial bout of infection, with major social, health and economic consequences, European health experts said on Thursday.Publishing a World Health Organization-led guidance report on the condition, often referred to as "long COVID" or "post-COVID syndrome," experts said around one in 10 COVID-19 patients are still unwell 12 weeks after their acute infection, and many suffer symptoms for far longer."This is a condition that can be extremely debilitating. Those suffering from it describe a varying combination of overlapping symptoms... (including) chest and muscle pain, fatigue, shortness of breath ... brain fog (and) many others," said Martin McKee, a professor at the European Observatory on Health Systems and Policies who led the report. Hans Kluge, the WHO's European regional director, said long-COVID could have "severe social, economic, health and occupational consequences.""The burden is real and it is significant," he said.He urged health authorities to listen to patients' concerns, take them seriously, and establish services to help them.Growing evidence from around the world points to many thousands of people experiencing long-COVID. The condition appears not to be linked to whether a patient had a severe or mild infection. An initial report by Britain's National Institute for Health Research last year suggested long-COVID may be not one condition, but multiple syndromes causing a rollercoaster of symptoms affecting the body and mind.Kluge noted that as with any new disease, much remains unknown about COVID-19."We need to listen and ... understand. The sufferers of post-COVID conditions need to be heard if we are to understand the long-term consequences and recovery from COVID-19," he said. "This is a clear priority for WHO (and) it should be for every health authority."