STOCKHOLM, Nov. 24 (Xinhua) -- Over 50,000 Swedes are estimated to suffer from long-COVID, Swedish Television (SVT) reported on Thursday.

Since 2020, 9,225 individuals in Sweden have been diagnosed with the condition at hospitals. However, as most sufferers instead seek help through primary care, the real number is believed to be considerably higher.

According to statistics from one of the Swedish regions, up to 50,000 people may be affected.

Some critics have alleged that the extreme fatigue that characterizes long-COVID may in fact be an imagined condition. However, Petter Brodin, a pediatrician and professor of immunology at the Karolinska Institute, told SVT that was not the case.

"What we know from all our studies of ... the more difficult cases, is that this is not delusional. It is very clearly caused by various physiological systems that have derailed and do not function as they should after this infection," Brodin said.

The plethora of symptoms of the disease means it can take time to diagnose long-COVID, he added. Brodin believes the real number of cases is "many many more" than those diagnosed by hospitals.

In September, the European Union launched the research project NEUROCOV to investigate neurological and neuropsychiatric complications following COVID-19 infections. Scientists from Belgium, Finland, Germany, Italy, Israel, the Netherlands, and Sweden were involved in the research.

"Different universities have different areas of competence and will attack this in different ways," said Anne-Marie Fors Connolly from Umea University, leader of Swedish research for the project.

"In Umea, we will use population data for the Swedish population to map risk factors and symptomatology for long-COVID."