WUHAN, China — The Huanan seafood market in the Chinese city of Wuhan, believed by many to be the origin of the COVID-19 pandemic, is sealed behind a blue perimeter fence. A large team of security staff chases away anyone who lingers. “We are just doing our job,” said a guard in black who ordered a Reuters reporter to delete footage recorded near the market’s main gates. He identified himself as a worker from the city government’s epidemic prevention and control team.