Spread of the New Coronavirus in the Year of the Rat

When the Middle East Respiratory Syndrome (MERS) was first identified as a coronavirus in 2012, the case fatality rate was very high at 35 percent; but thankfully there was very low human-to-human transmission. Such transmission happened in healthcare settings, or to a much lesser extent in households where people caring for an infected person had close contact. 

Camels were identified as a “reservoir host” for MERS, with infection primarily caused through direct contact with camel fluids. As evidence of very low human-to-human transmission, there were no MERS cases reported in either the 2012 or 2013 Hajj pilgrimage to Mecca, although an Indonesian couple may have caught MERS in the 2014 Hajj.

In China, there is an even larger annual migration tied to the lunar calendar – as the lunar New Year starts on Saturday, January 25. This is normally a time of happiness and celebration during family reunions. This year, there will be fear and foreboding over the new coronavirus, which emerged in December from a seafood market in Wuhan, Central China. On January 21, Chinese health authorities confirmed human-to-human transmission of the coronavirus. Fortunately, the case fatality rate seems to be quite low, just a few percent.

The best protection against infection is isolation: but this is the worst weekend for isolation. Wuhan is in lockdown, all transport networks – including rail, bus, underground and ferries – have been suspended in Wuhan, and all residents have been ordered to wear masks in public places and at work. With three billion trips taken over the Chinese New Year period, even a tiny infection rate of one in a million trips would escalate the number of infections by an order of magnitude.

Prof. Neil Ferguson, one of the world’s leading epidemiologists and an advisor on the RMS infectious disease model, reckons that pre-New Year official Chinese figures on the number of cases are likely to be an underestimate. This view is corroborated by infectious disease experts at Hong Kong University, who estimate about 1,500 infections in China, mostly in the city of Wuhan (pop. ~11 million), but some cases in twenty other Chinese cities. 

An emergent contagious coronavirus is inevitably a global threat. Given the international scale of Chinese mass tourism, it would not be surprising for cases to be identified in many more countries in Asia, besides Thailand, South Korea and Japan, as well as for cases to be confirmed on other continents.   

From Wuhan Airport, there are flights to over a hundred destinations in twenty countries. These include London, Moscow, Paris, Rome, New York, San Francisco, Bangkok, Tokyo and Seoul. Airport screening has been established to identify fevered flyers, but already a Seattle resident has returned from Wuhan harboring the coronavirus.

Surveillance is vital for control of this emergent threat and preventing a global health crisis. An indicator of the scale of the risk posed by the new coronavirus is an accurate tally of cases and fatalities at the beginning of February.

Rather inauspiciously, the Chinese New Year is the year of the rat. New Year greetings should hope for health and resilience against the latest lethal human disease to emerge from contact with animals.