In late December 2019 a number of severe cases of pneumonia were reported in Wuhan, China. Testing quickly ruled out the known SARS and MERS coronaviruses (commonly referred to as SARS-CoV and MERS-CoV, respectively). But on 8 January 2020, sequencing of the virus showed that it belonged to this same family of viruses.

Estimated numbers by 2 February were over 17,000 and 361 deaths in mainland China. Other cases have occurred in Australia, Cambodia, Canada, Finland, France, Germany, Hong Kong, India, Italy, Japan, Macau, Malaysia, Nepal, Philippines, Russia, Singapore, South Korea, Spain, Sri Lanka, Sweden, Taiwan, Thailand, the US, the United Arab Emirates and Vietnam. The UK has two confirmed cases to date.

This is a fast-moving issue and should be read as correct at the time of writing.

Where did the virus come from?

Many people among the early reported cases had visited the Wuhan Seafood Market, which sells a large number of live animals. The virus genome suggests that it evolved from an animal coronavirus. Further analysis suggests it is related to bat coronaviruses. It is also likely that both MERS- and SARS-coronaviruses came from bats. Reports of connections with snakes are very early and research has not yet been replicated.

Does the new coronavirus spread human-to-human?

Initially it did not seem to be passing from one human to another. But on 23 January, the World Health Organization’s (WHO) Emergency Committee noted that transmission was occurring. In epidemiology an ‘R0’ value is the number of people infected by each new carrier or case. Current estimates for the virus’s R0 vary from 1.4 to 3.8. This suggests that a carrier of the virus can infect on average up to four people. This is similar to SARS-CoV and MERS-CoV. Also like in the case of SARS and MERS, some novel coronavirus carriers are “super-spreaders” and can infect more than 10 close contacts.

How is the new coronavirus transmitted?

This has not yet been confirmed. SARS-CoV and MERS-CoV spread via droplets of saliva, urine, faeces and blood. Transmission can be from direct contact with these or contaminated surfaces. Therefore, new coronavirus cases need to be promptly isolated with good infection control practices. 

What is the mortality rate?

Epidemiologists use the case-fatality rate (CFR) when talking about the deadliness of an infection. CFR is hard to estimate early in an epidemic because many patients have not yet, and may not, recover. Current estimates in China are that 21% of patients get severely ill and 3% die. The first 17 people who died were aged 48–89 years, with an average age of 73. Many of them had underlying health conditions. 

What did we learn from the SARS-CoV outbreak?

The risk of transmission of SARS-CoV during the outbreak in 2003 was highest after five days of symptoms – early isolation and infection control was therefore highly effective. One study suggests that the new coronavirus can spread before symptoms (fever and cough) take hold. At the time of writing, this is unconfirmed but would make its control much more difficult. 

Much can also be learnt from how Toronto dealt with the SARS-CoV outbreak in 2003. The response included closing schools and restricting public transport. Hospitals were also closed to elective patients and cases were isolated in dedicated wards. The staff and visitors of those patients were also quarantined for the duration of the outbreak. While these were effective measures, they cost Toronto about $1 billion and severely disrupted normal life for residents.

How can the UK public be protected?

There have been no confirmed cases of the new coronavirus in the UK. Recognition and diagnosis of infected cases is very important. Our experience of coronaviruses is that many infections are sub-clinical – they don’t produce symptoms for most people. Current models estimate that only 5% of cases in Wuhan have been diagnosed. Key to control is therefore surveillance and early isolation of cases. The R0 value means that 60–70% of transmissions must be prevented using control measures.

GPs and hospitals in the UK have already been given advice by Public Health England. Previous experience with coronaviruses has taught us that spread in healthcare facilities is a high risk. Patients should be isolated from others, with anyone entering the room needing to wear respirators and protective gowns, gloves and eye protection. Only essential visitors should be allowed in. Waste and specimens should be processed in a way that avoids any transmission.

Enhanced monitoring is in place for all direct flights from Wuhan to the UK to check whether anyone feels unwell. Models suggest that the travel restrictions that China has put in place will have a moderate impact. A 99% reduction in travel will reduce the size of the epidemic by around 25%. 

How do we prevent emerging infections?

The source of many emerging infections are animals. We therefore need to be able to detect viruses capable of transmission to humans from an animal before they jump species. Since the SARS-CoV pandemic, there has been a focus on global health security. Through this, local public health surveillance systems have been strengthened. However, much of the attention has focused on humans and less on animals. Wildlife trade continues to be a threat to both human health and biodiversity. More regulation of wildlife trade and animal health is needed to protect humans and the environment.

About the author: Grant Hill-Cawthorne is Head of the Parliamentary Office of Science and Technology (POST).

POST provides balanced and accessible overviews of research from across the natural, physical and social sciences, engineering and technology, placing findings in a policy context for MPs and Lords. See our latest infection-related publications on reservoirs of antimicrobial resistance, reducing UK use of antibiotics in animals, antimicrobial resistance and immunisation, and climate change and vector-borne disease in humans.