Until January, these markets sold animals such as live civets, wolf pups and pangolins kept in small cages, often in filthy conditions, where they incubate diseases that can spill into human populations.
Wild animals have always carried viruses, but a global wildlife trade worth billions of dollars, agricultural intensification, deforestation and urbanisation have all brought people closer to wildlife.
Some 70 per cent of emerging infectious diseases in humans are of zoonotic origin, scientists say, and nearly 1.7 million undiscovered viruses may exist in wildlife.
Previous global epidemics, including severe acute respiratory syndrome (Sars) and Ebola, were linked to viruses transmitted by animals to people.
The letter calls on the WHO to recommend to governments worldwide that they bring in permanent bans on live wildlife markets and act to close down or limit trade in wildlife to reduce the threat to human health.
The letter was co-ordinated by the wildlife charity Born Free and its Lion Coalition partners, and is backed by organisations including the Bat Conservation Trust, International Fund for Animal Welfare and the Zoological Society of London.
Dr Mark Jones, head of policy at Born Free, said: "Once Covid-19 is hopefully behind us, returning to business as usual cannot be an option."
The United Nations' biodiversity chief said she supported such a global ban on wildlife markets. Elizabeth Maruma Mrema said there were clear links between the destruction of nature and new human illnesses.
Dr Anthony Fauci, America's top infectious diseases expert and the face of the national response to the pandemic, has said that the world community should pressure China and other nations that host such markets to shut them down.
"It just boggles my mind how - when we have so many diseases that emanate out of that unusual human-animal interface - that we don't just shut it down," Fauci told Fox News.
A survey by the wildlife charity WWF, which was conducted in March among 5000 participants from Hong Kong, Japan, Burma, Thailand and Vietnam, found 93 per cent supported action by their governments to eliminate illegal and unregulated markets.
Marco Lambertini, director general of WWF International, said: "Taking action now, for humans as well as the many wildlife species threatened by consumption and trade, is crucial for all of our survival."
