Lots of discussion today on the future of the coronavirus outbreak (2019_nCoV) on social media. The R_0 estimates reported yesterday, see, raised interesting comments. Some, apparently, thought that the end was near, where others criticized modelling if based on few cases only. Terms as “irresponsible” science were posted. The opposite is true.
Predicting the faith of a new outbreak is essential for a proper public health response. Establishing an opinion (and response) on just looking at the data as they come in, is as good as hand waving. Mathematical modellers establish their estimates on a mechanistic model, reflecting key characteristics of the disease, and on observed data and explicitly formulated assumptions where data are lacking. Everything is (or should be) transparent and can be reproduced by others. The mathematical parts may not be understandable to all physicians (including me), but so are the technological parts of an MRI scan or deep-sequencing (that we blindly trust). If you don’t trust mathematics ask an expert for help. The other important aspect of modelling is that the uncertainties are quantified, and that the robustness of estimates of, for instance R_0, can be tested with sensitivity analyses for parameters where uncertainty is large. Modellers (usually) are fully aware of these uncertainties and extensively discuss them. If ignorant readers communicate the results without the nuances, shoot the messenger, not the modeller!
So, back to the model estimates of today. There was an update by the MRC Centre for Global Infectious Disease Analysis from Imperial College of London (@MRC_outbreak), a team few would not consider to be highly authoratative. Their R_0 estimate of the day was 2.6 (95% CI 1.5-3.5). That may seem less dramatic than 3.6 (the catch of yesterday, by others), but would still require that infection control measures must block well >60% of transmission to be successful.
So far, the case-fatality rate seems low, and many subjects have mild symptoms. That sounds good, but could also be bad news if the latter are capable to transmit the virus. To me (and the modellers, I hope), that is the big unknown yet. The family history published in Lancet yesterday is not reassuring. One of six family members had no disease symptoms at all, but appeared to have similar pulmonary CT abnormalities as the others when tested on requested of the– worried – family members. The presence of 2019_nCoV in respiratory samples was not tested in this asymptomatic subject. Therefore, no proof of transmissibility in the absence of symptoms, but negative tests would have been more reassuring.
Interesting times, to be continued.