Three researchers at the Wuhan Institute of Virology in China applied for hospital treatment in November 2019. The case emerges from a U.S. secret intelligence report obtained by the Wall Street Journal.

According to the report, the researchers had similar symptoms to the coronavirus disease and the common seasonal flu.

According to the Wall Street Journal, the intelligence report includes information on the number of researchers affected, the timing of their illness, and hospital visits.

According to the magazine, intelligence agencies familiar with the report expressed mixed views on the strength of the report’s evidence.

One unnamed source said more research and confirmatory evidence is needed.

According to another source, the intelligence is very high quality and accurate.

However, he noted that the document does not explain why the researchers fell ill.

The information from the intelligence report came to light just before the WHO leadership is scheduled to meet to discuss the next step in the investigation into the origins of the Covid-19 virus.

A spokesman for the U.S. National Security Council declined to comment on the Wall Street Journal, but said the Joe Biden administration still has serious questions about the early stages of the corona pandemic.

According to the Biden administration, the WHO and international experts should study all plausible theories about the origin of the virus.

Many experts believe that the Covid-19 virus began to spread in November 2019 in Wuhan City.

According to China, the first confirmed corona case was detected in December 2019.

An international team of experts led by the WHO visited Wuhan early in the year and published a report on its research in March.

The report found that the virus is most likely to have spread to humans from bats through another animal.

However, the United States and the European Union, among others, have called for more transparent research into the origin of the virus and better access to research data and samples from early coronavirus cases.

To date, the Wuhan Virological Institute has not shared information from its extensive study on the presence of coronavirus in bats.

China has repeatedly denied the virus has spread from its laboratories.

The Chinese Foreign Ministry commented to the Wall Street Journal on Sunday that a WHO research team investigating the origin of the virus visited the Wuhan Institute in February and considered it highly unlikely that the virus had spread from the laboratory.