How dangerous is the virus?

A pathogen’s harmfulness is determined by the combination of its transmission rate (Ro, reproductive number) and its case fatality rate (CFR), so we'll examine these two parameters below.

How contagious is the Wuhan Coronavirus? (Ro)

The attack rate or transmissibility (how rapidly the disease spreads) of a virus is indicated by its reproductive number (Ro, pronounced R-nought or r-zero), which represents the average number of people who will catch the disease from a single infected person.

For the Wuhan Coronavirus, this parameter is estimated to be between 2.0 and 3.1, according to preliminary studies ^[5][6], with one study providing an estimate of 2.6 with an uncertainty range of: 1.5-3.5^[7]. The WHO noted on January 23 that human-to-human transmission was occurring and a preliminary Ro estimate of 1.4-2.5^[13]. Based on these numbers, on average every case of Wuhan Coronavirus would create between 2 and 3 new cases. An outbreak with a reproductive number of below 1 will gradually disappear.

For comparison, the Ro for the common flu is 1.3 and for SARS it was 2.0.

Fatality Rate (case fatality ratio or CFR) of the Wuhan Coronavirus

See full details: Wuhan Coronavirus Fatality Rate

The novel coronavirus' case fatality rate is currently estimated at around 2%, according to the WHO ^[16] on January 29, 2020. A prior estimate ^[9] had put that number at 3%, between 2% and 4%). Fatality rate can change as a virus can mutate, according to epidemiologists.

Once the province Hubei (where the epicenter Wuhan is situated) is removed from the calculation, the national (China) mortality rate drops to 0.3%. Within the Hubei province, the mortality rate is about 1% when excluding the city of Wuhan (where it is 5.5%).

For comparison, the case fatality rate with seasonal flu is less than 0.01% (1 death per every 10,000 cases)^[8]. Mortality rate for SARS was 10%, and for MERS 34%.

Incubation Period (how long it takes for symptoms to appear)

The Wuhan novel coronavirus appears to be contagious before symptoms appear, as it is estimated to have an incubation period of 10 to 14 days, according to Ma Xiaowei, the director of China’s National Health Commission^[11].

The United States' CDC estimates the incubation period for 2019-nCoV to be between 2 and 14 days ^[10].

This means that symptoms of the novel coronavirus (2019-nCoV) may appear in as few as 2 days or as long as 14, during which the virus is contagious but the patient does not display any symptom (asymptomatic transmission).

Age and conditions of Coronavirus cases

According to the WHO Situation Report no. 7 issued on Jan. 27:

• The median age of cases detected outside of China is 45 years, ranging from 2 to 74 years.
• 71% of cases were male.

The WHO, in its Myth busters FAQs, addresses to the question: "Does the new coronavirus affect older people, or are younger people also susceptible?" by answering that:

• People of all ages can be infected by the new coronavirus (2019-nCoV).
• Older people, and people with pre-existing medical conditions (such as asthma, diabetes, heart disease) appear to be more vulnerable to becoming severely ill with the virus.

Worldometer is conducting further research on case and deaths demographics and will update soon with its findings.

WHO Risk Assessment: Global Emergency

See full details: WHO coronavirus updates

On January 30, the World Health Organization has declared the coronavirus outbreak a Global Public Health Emergency.

For more information from the WHO regarding novel coronavirus: WHO page on Novel Coronavirus (2019-nCoV)