Early Transmission Dynamics in Wuhan, China, of Novel Coronavirus–Infected Pneumonia
Analysis of first 425 confirmed cases in Wuhan conducted to determine epidemiologic characteristics of novel coronavirus (2019-nCoV)–infected pneumonia found evidence that human-to-human transmission has occurred among close contacts since the middle of December 2019.
Source:
New England Journal of Medicine
SPS commentary:
The study found that the majority of cases (55%) with onset before January 1, 2020, were linked to the Huanan Seafood Wholesale Market, as compared with 8.6% of the subsequent cases. The mean incubation period was 5.2 days, with the 95th percentile of the distribution at 12.5 days. In its early stages, the epidemic doubled in size every 7.4 days.
An editorial notes that for the third time in as many decades, a zoonotic coronavirus has crossed species to infect human populations, and like outbreaks caused by two other pathogenic human respiratory coronaviruses (severe acute respiratory syndrome coronavirus [SARS-CoV] and Middle East respiratory syndrome coronavirus [MERS-CoV]), 2019-nCoV causes respiratory disease that is often severe.
Another study in the Journal has sequenced the viral genome, and these results in conjunction with other reports show that it is 75 to 80% identical to the SARS-CoV and even more closely related to several bat coronaviruses. It can be propagated in the same cells that are useful for growing SARS-CoV and MERS-CoV, but notably, 2019-nCoV grows better in primary human airway epithelial cells than in standard tissue-culture cells, unlike SARS-CoV or MERS-CoV.
The editorial highlights that much still needs to be learned about this infection. Most important, the extent of interhuman transmission and the spectrum of clinical disease need to be determined. A second key question is identification of the zoonotic origin of the virus. Given its close similarity to bat coronaviruses, it is likely that bats are the primary reservoir for the virus. It suggest tjat transmission of 2019-nCoV probably occurs by means of large droplets and contact and less so by means of aerosols, on the basis of experience with SARS-CoV and MERS-CoV. Public health measures, including quarantining in the community as well as timely diagnosis and strict adherence to universal precautions in health care settings, were critical in controlling SARS and MERS, thus institution of similar measures will be important and, it is hoped, successful in reducing the transmission of 2019-nCoV.
A Perspective in the journal highlights key questions for impact assessment and a letter describes importation and human-to-human transmission of a novel Coronavirus in Vietnam in one family cluster originating from a Chinese man.