Saturday, January 25, 2020

Wuhan Coronavirus

[ See update: COVID-19 Notes or use the search label Epidemics.]

The Wuhan coronavirus outbreak (see WHO resource) caused me to look back at a paper I wrote in 2003 with A. Zee. We were motivated at the time by the recent SARS outbreak. Some results in the paper may be relevant today.

For Wuhan coronovirus the important parameters such as R0 (average number of secondary cases caused by a single infected individual) and lethality are still to be determined.
Global Spread of Infectious Diseases (ArXiv)

S. Hsu, A. Zee

We develop simple models for the global spread of infectious diseases, emphasizing human mobility via air travel and the variation of public health infrastructure from region to region. We derive formulas relating the total and peak number of infections in two countries to the rate of travel between them and their respective epidemiological parameters.
From the conclusions:
One interesting conclusion from our models is that typical international mobility – the probability per unit time of international travel for a given infected individual, estimated at mi→j ∼ 10−5 per week – is still sufficiently small that a country with well-developed public health infrastructure (effectively, a negative eigenvalue λ) can resist an epidemic even when other more populous countries experience complete saturation. In the quasi-realistic simulation 1 (figures (1),(2)), of order 10^5 infections occur in country 2, even though the disease has swept completely through country 1. In reaching this conclusion, we kept the mobility parameter fixed during the outbreak, and did not assume any draconian quarantine on international travelers arriving in country 2. Such measures would reduce the number of infections in country 2 considerably. Of course, this conclusion assumes that the public health infrastructure in country 2 remains robust during the outbreak. In the nonlinear simulation 3 (figures (6), (7)), we see that a breakdown in the medical system can lead to grave consequences.

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