Coronavirus may be the 'Disease X' WHO cautioned about years ago

The World Health Organization cautioned years ago that a mysterious “disease X” could spark an international contagion. The new coronavirus, with its ability to quickly morph from mild to deadly, is emerging as a contender.

From recent reports about the stealthy ways the so-called Covid-19 virus spreads and maims, a picture is emerging of an enigmatic pathogen whose effects are mainly mild, but which occasionally — and unpredictably — turns deadly in the second week. In less than three months, it’s infected about 77,000 people, mostly in China, and killed more than 2,200.

“Whether it will be contained or not, this outbreak is rapidly becoming the first true pandemic challenge that fits the disease X category,” Marion Koopmans, head of viroscience at Erasmus University Medical Center in Rotterdam, and a member of the WHO’s emergency committee, wrote on Wednesday in the journal Cell.

The disease has now spread to more than two dozen countries and territories. Some of those infected caught the virus in their local community and have no known link to China, the US Center for Disease Control and Prevention said.

“We are not seeing community spread here in the United States yet, but it’s very possible — even likely — that it may eventually happen,” Nancy Messonnier, director of the CDC’s National Center for Immunization and Respiratory Diseases, told reporters on Friday.

Unlike SARS, its viral cousin, the Covid-19 virus replicates at high concentrations in the nose and throat akin to the common cold, and appears capable of spreading from those who show no, or mild, symptoms. That makes it impossible to control using the fever-checking measures that helped stop SARS 17 years ago.

Spreading surreptitiously

A cluster of cases within a family living in the Chinese city of Anyang is presumed to have begun when a 20-year-old woman carried the virus from Wuhan, the outbreak’s epicentre, on January 10 and spread it while experiencing no illness, researchers said Friday in the Journal of the American Medical Association.

Five relatives subsequently developed fever and respiratory symptoms. Covid-19 is less deadly than SARS, which had a case fatality rate of 9.5 per cent, but appears more contagious. Both viruses attack the respiratory and gastrointestinal tracts, via which they can potentially spread.

While more than 80 per cent of patients are reported to have a mild version of the disease and will recover, about one in seven develops pneumonia, difficulty breathing and other severe symptoms. About 5 per cent of patients have critical illness, including respiratory failure, septic shock and multi-organ failure. “Unlike SARS, Covid-19 infection has a broader spectrum of severity ranging from asymptomatic to mildly symptomatic to severe illness that requires mechanical ventilation,” doctors in Singapore said in a paper in the same medical journal Thursday.

“Clinical progression of the illness appears similar to SARS: patients developed pneumonia around the end of the first week to the beginning of the second week of illness.” Older adults, especially those with chronic conditions, such as hypertension and diabetes, have been found to have a higher risk of severe illness. Still, “the experience to date in Singapore is that patients without significant co-morbid conditions can also develop severe illness,” they said.