Health experts issued an ominous warning about a coronavirus pandemic 3 months ago. Their simulation showed it could kill 65 million people.

Eric Toner, a scientist at the Johns Hopkins Center for Health Security, wasn't shocked when news of a mysterious coronavirus outbreak in Wuhan, China, surfaced in early January.

A coronavirus

Less than three months earlier, Toner had staged a simulation of a global pandemic involving a coronavirus.

Coronaviruses typically affect the respiratory tract and can lead to illnesses like pneumonia or the common cold. 

A coronavirus was also responsible for the outbreak of severe acute respiratory syndrome in China, which affected about 8,000 people and killed 774 in the early 2000s.

"I have thought for a long time that the most likely virus that might cause a new pandemic would be a coronavirus," Toner said.

The outbreak in Wuhan isn't considered a pandemic, but the virus has been reported in Thailand, Japan, South Korea, Taiwan, Vietnam, Singapore, and Saudi Arabia.

 The US reported its first case on Tuesday: a man in his 30s living in Washington's Snohomish County, north of Seattle, who recently visited China.

So far, the virus has killed 18 people and infected more than 630.

"We don't yet know how contagious it is. We know that it is being spread person to person, but we don't know to what extent," Toner said. "An initial first impression is that this is significantly milder than SARS. So that's reassuring. On the other hand, it may be more transmissible than SARS, at least in the community setting."

Toner's simulation of a hypothetical deadly coronavirus pandemic suggested that after six months, nearly every country in the world would have cases of the virus. Within 18 months, 65 million people could die.