The coronavirus epidemic has understandably caused much anxiety throughout the world. Uncertainty about what the new disease portends has wreaked havoc on the cruise ship industry and the airlines. The stock market which is always twitchy is still uncertain as to whether it should take a swan dive which is appropriate as COVID-19, as the virus has been named, is a classic black swan. In the immortal words of the Monty Pythons: “Nobody expects the Spanish Inquisition.” The entire planet is on edge about something that no one was aware of just a few months ago.
The Journal of the American Medical Association has released two articles about this new pathogen to its online site. The first: Clinical Characteristics of 138 Hospitalized Patients With 2019 Novel Coronavirus–Infected Pneumonia in Wuhan, China is a report from the medical center, Zhongnan Hospital of Wuhan University, in Wuhan where the virus first surfaced. Given that the paper originated in China, where censorship is so prevalent that a cautious interpretation is always required, it seems to be an accurate description of the epidemiologic and clinical characteristics of COVID-19.
As everyone now knows, the disease was recognized in December of last year in Wuhan. It started as a cluster of acute respiratory illness. The best current explanation for its start in humans is that the virus jumped to humans from animals sold illegally in the Hunan Seafood Wholesale Market. The viral genome was rapidly sequenced. It is a distinct form of betacoronavirus related to those that cause human acute respiratory syndrome (SARS) and Middle East respiratory syndrome (MERS).
The Wuhan patients had a mean age of 56. Thus far the disease seems to spare children under 15 for reasons that are not clear. Typical symptoms included fever and dry cough. Imaging showed patchy ground glass opacity in the lungs. Remember, these are patients hospitalized with pneumonia and thus reflect only the severe end of the disease spectrum. The median time from first symptom to dyspnea was 5 day, to hospitalization 7 days, and to Acute Respiratory Distress Syndrome 8 days. Of the 138 patients, 6 died. No effective specific treatment for this disorder yet exists. Similarly, a vaccine against the virus has yet to be developed. But we’re only about 2 months into this disease.
A second paper in the online JAMA, Preparation for Possible Sustained Transmission of 2019 Novel Coronavirus, considers the possible transmissibility and severity of COVID-19 infections. Neither the SARS nor MERS epidemics had the combination of both high transmissibility and severity that seems to be the case for the new virus. Transmissibility is measured by R0; it is the basic reproduction number. If it is less than 1 the infection will likely eventually spontaneously fade away. A value greater than 1 indicates the potential for sustained transmission.
Both the SARS and MERS viruses caused severe disease, but were of low transmissibility and thus did not cause a worldwide catastrophe. It is too soon to tell if COVID-19 has the bad combination of these two variabilities such that a deadly pandemic may result. Early estimates of this new virus’s R0 place it at more than 2. The WHO has said that 14% of COVID-19 infections are severe, but as the authors of this second JAMA paper linked above observe, early estimates of severity are usually higher during the first phase of an epidemic.
Modeling for a severe epidemic in the US that might result from COVID-19 infection, should it gain from purchase here, suggest a worst case scenarios of more than 4 million hospitalizations and as many as half a million deaths. About 60,000 ventilators would be needed and perhaps 7 billion surgical masks. Obviously, it’s better to prevent an epidemic here than to deal with it.
Plans for containing an influenza epidemic in the US are in existence which could be used to combat COVID-19. These plans presumably would be implemented if it appears that COVID-19 infection threaten to achieve epidemic proportions in the US. “Effective prevention and and control will not be easy if there is sustained transmission and will require full attention of public health, federal and local governments, the private sector, and every citizen.” This conclusion is an understatement.