Saturday, May 3, 2014

First US MERS case announced

Photo: MERS-CoV particles as seen by negative stain electron microscopy. Virions contain characteristic club-like projections emanating from the viral membrane.Yesterday the first case of Middle East respiratory syndrome (MERS) observed in the US was announced. The case is a man who flew to Chicago, Illinois from Riyadh, Saudi Arabia by way of London, England. After landing in Chicago, he took a bus to Indiana. He arrived in the US on April 24 and began experiencing shortness of breath, coughing, and fever on April 27. He presented to a community hospital in Munster, Indiana, on April 28; because of his symptoms and travel history, the man was tested for the MERS coronavirus.

Understandably, the story is being covered widely in the press. One can learn more about MERS from several sources. The ECDC MERS-CoV epidemiological update as of April 30 is an excellent summary of MERS globally, and additional resources can be found at the CDC MERS Website. UPMC has also published a nice summary of the global situation. 

It would be interesting to utilize mathematical modeling to estimate where, assuming the patient was infectious while on the bus and planes, new cases might be likely to develop, geographically speaking. Such analysis could be helpful for instituting intensified surveillance in the places most likely to have such cases; using models, it may be possible to forecast the most likely cities. A rich set of methods, spanning the 1960s to the present, has been developed to understand the spatio-temporal spread of influenza and those could probably be adapted for such purposes if data on domestic bus, rail, and air travel since the plane landed is available. And while it's true that significant uncertainties in latency and incubation periods, transmission rates, and other epidemiologic parameters exist, there are techniques that allow us to estimate the effects of such uncertainties on model results.

Gathering the data, especially the transportation data, may be difficult. A NYT article this morning noted
The typical incubation period for MERS is five days, and the patient is not known to have infected anyone else. Airline passenger lists will be used to contact everyone who sat near him.

But because bus companies often do not know who bought tickets or who sat where, “that bus ride may be a challenge,” said Tom Skinner, a C.D.C. spokesman.
Information on rail passengers may be similarly difficult.

The time to develop adaptable modeling capabilities and gather such data is before new diseases emerge and spread. Of course, it's not possible to anticipate specific details about a new disease prior to emergence, but we do have some data on MERS already, plus lots of insight into how respiratory diseases spread in general. 

Regardless of models, it will be interesting to watch the MERS situation develop globally in the coming months.

(image source: CDC)

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