Epidemiology and Pathogenesis 

All ages are susceptible. Infection is transmitted through large droplets generated during coughing and sneezing by symptomatic patients but can also occur asymptomatic person and before onset of symptoms. Studies have shown higher viral loads in the nasal cavity as compared to the throat with no difference in viral burden between symptomatic and asymptomatic people. Patients can be infectious as long as the symptoms last and even on clinical recovery. Some people may act as super spreaders; a UK citizen who attended a conference in Singapore infected 11 other people while staying in a resort in the French Alps and upon return to the UK. These infected droplets can spread 1-2 m and deposit on surfaces. The virus can remain viable on surfaces for days in favourable atmospheric conditions but are destroyed in less than a minute by common disinfectants like sodium hydro chlorite, hydrogen peroxide etc.

Infection is acquired either by inhalation of these droplets or touching surfaces contaminated by them and then touching the nose, mouth and eyes. The virus is also present in the stool and contamination of the water supply and subsequent transmission via aerosolization/feco oral route is also hypothesized. As per current information, trans placental transmission from pregnant women to their fetus has not been described. However, neonatal disease due to post-natal transmission is described. The incubation period varies from 2 to 14 days [median 5 days] Studies have identified angiotensin receptor 2 (ACE2) as the receptor through which the virus enters the respiratory mucosa.

The basic case reproduction rate (BCR) is estimated to range from 2 to 6.47 in various modelling studies. In comparison, the BCR of SARS was 2 and 1.3 for pandemic flu H1N1 2009.