Since mid-December 2019, several cases of a pneumonia-like disease (with symptoms including fever, difficulty in breathing, cough and invasive lesions on both lungs) of unknown cause have emerged in the central Chinese city of Wuhan (WHO). Chinese authorities made a preliminary determination that the causative agent is a novel coronavirus (2019-nCoV), and other respiratory pathogens have been ruled out as the cause (WHO). A consortium of researchers, government agencies and institutes released six sequences of the coronavirus associated with the outbreak in Wuhan on and on Global Initiative on Sharing All Influenza Data (GISAID). Phylogenetic analysis indicated that the new virus clusters with the severe acute respiratory syndrome (SARS)-related coronavirus clade, and the virus has since been isolated.

So far ~400 confirmed infections with the new coronavirus as well as several deaths have been reported in China (Nature), although scientists at Imperial College in London estimated that the number of cases in Wuhan was likely to be closer to 1,700. In addition, the virus has spread to Thailand, Japan, South Korea and the United States, and additional cases in other countries are likely.

Coronaviruses comprise a large family of viruses that cause respiratory and intestinal infections in animals and humans, including Middle East respiratory syndrome (MERS) and SARS. SARS first emerged in the Guangdong province, China, causing the 2002–2003 epidemic. The virus spread rapidly among humans, affecting ~8,000 individuals in more than 30 countries and causing the death of ~800 patients. SARS and MERS coronaviruses likely originated in bats and have been transmitted directly to humans from market civets and dromedary camels.

On the basis of initial epidemiological investigations, the pneumonia-like cases in Wuhan have been linked to a seafood and animal market, which might point to a zoonotic origin of the new coronavirus (CDC). The market has since been closed for environmental sanitation and disinfection, and environmental specimens from that and other markets are being collected and tested. The UN health agency has urged China to continue the efforts to identify the source, reservoirs and possible intermediate hosts of the new virus. The Wuhan Health Commission reported that “the possibility of limited human-to-human transmission cannot be ruled out” and infections of the health-care workers as well as infections of family members suggest that person-to-person spread is occurring (Nature).

Response measures have been implemented in Wuhan, and ongoing investigations are focussing on understanding the epidemiology, the source, clinical manifestation, transmission routes, global risk assessment and the development of diagnostic tests(Science; WHO).The WHO has called a meeting to decide whether to declare a public-health emergency of international concern (The Washington Post).