When it comes to emerging infectious diseases – those newly recognized in humans or in new locations – it is not only what we know that matters but also what we do not know.

An outbreak of a new coronavirus first reported in Wuhan, China, which has so far led to more than 500 confirmed cases and multiple deaths across five countries (and two continents) has prompted the question from several corners of the world: Should we be worried?

Although expert teams coordinated by the World Health Organization (WHO) are working on key questions to get answers as soon as possible, the level of uncertainty is still high.

We do not yet know exactly how deadly the disease is, how best to treat those who get sick, precisely how it is spreading, nor how stable the virus is. It is thought that the virus spread from an animal source, but the exact source is yet to be confirmed and the disease is now in human populations and appears to be spreading from human to human.

It is such uncertainty, inherent in emerging infectious disease outbreaks, that warrants concern. Until they are resolved, it is appropriate for the world to be concerned. It is useful to remember that most established scourges of humanity such as HIV, influenza and tuberculosis likely started as emerging infectious diseases that jumped the species barrier from animals to humans.

Shortly after the Chinese authorities reported the first cases of ‘mystery pneumonia’ in Wuhan, China, to WHO, the virus causing the disease was isolated and identified as being part of the coronavirus family. It belongs to the same virus family as SARS, a highly contagious and life-threatening coronavirus that caused a nine-month epidemic in 2003 that affected 26 countries and resulted in more than 8,000 infections and nearly 800 deaths.

A second novel coronavirus that emerged in 2012 and persists today – MERS, or Middle East Respiratory Syndrome – is less contagious (spread by close contact rather than coughing and sneezing).

The differences between the SARS coronavirus and the MERS coronavirus highlight that, despite belonging to the same virus family, pathogens do not necessarily behave in the same way. It is as yet unknown whether the new virus is, or will turn out to be, more like SARS or MERS, or neither. 

Chinese authorities have confirmed that there is human-to-human transmission. However, it is not yet established whether it is sustained, which would make the outbreak more difficult to control. As of 23 January, the number of cases range from 500 confirmed cases up to an estimated 1,700 cases, according to a disease outbreak model by Imperial College London.

Likewise, we do not know to what extent the virus is able to mutate and if so, how rapidly. Generally, coronaviruses are known to be able to mutate, with the risk that a less contagious form of the virus becomes highly contagious. This could have an impact not only on the transmission pattern and rate but also the death rate. The virus could change in either direction, to become either more or less of a threat.

It is important to take a precautionary approach while uncertainty persists. It is also important not to overreact and for measures to be scientifically sound. Concern over this outbreak is due, but panic is not.

Three virtual networks of experts supporting the response – one of virologists, one of epidemiologists and one of clinicians – are working on the key pieces of the jigsaw puzzle: watching the virus, watching the transmission patterns, and watching the people who have been infected. It is crucial to maintain the ongoing investigation of the disease, stay focused on the science and to keep sharing the necessary information.

Professor Heymann, who previously led the World Health Organization’s response to SARS and has been advising the organization on its response to the coronavirus, outlines the key facts relating to this outbreak and reflect on the challenges it poses. 

An outbreak of a new coronavirus first reported in Wuhan, China has so far spread to dozens of countries, led to tens of thousands of confirmed cases and almost 2,000 deaths. The World Health Organization has declared the situation a global health emergency thereby prompting questions from around the world about how worried the public should be and how can governments, media, civil society and the global health community best tackle new infectious disease outbreaks?

What do we know – and what do we not know – about this coronavirus at the moment? What lessons learned from previous outbreaks have been applied – and not applied – to this outbreak? How can governments and the media balance public awareness and the risk of panic? And what measures can be taken to reduce the risk of stigma and discrimination of populations during this and other outbreaks?

When it comes to emerging infectious diseases – those newly recognized in humans or in new locations – it is not only what we know that matters but also what we do not know.

An outbreak of a new coronavirus first reported in Wuhan, China, which has so far led to more than 500 confirmed cases and multiple deaths across five countries (and two continents) has prompted the question from several corners of the world: Should we be worried?

Although expert teams coordinated by the World Health Organization (WHO) are working on key questions to get answers as soon as possible, the level of uncertainty is still high.

We do not yet know exactly how deadly the disease is, how best to treat those who get sick, precisely how it is spreading, nor how stable the virus is. It is thought that the virus spread from an animal source, but the exact source is yet to be confirmed and the disease is now in human populations and appears to be spreading from human to human.

It is such uncertainty, inherent in emerging infectious disease outbreaks, that warrants concern. Until they are resolved, it is appropriate for the world to be concerned. It is useful to remember that most established scourges of humanity such as HIV, influenza and tuberculosis likely started as emerging infectious diseases that jumped the species barrier from animals to humans.

Shortly after the Chinese authorities reported the first cases of ‘mystery pneumonia’ in Wuhan, China, to WHO, the virus causing the disease was isolated and identified as being part of the coronavirus family. It belongs to the same virus family as SARS, a highly contagious and life-threatening coronavirus that caused a nine-month epidemic in 2003 that affected 26 countries and resulted in more than 8,000 infections and nearly 800 deaths.

A second novel coronavirus that emerged in 2012 and persists today – MERS, or Middle East Respiratory Syndrome – is less contagious (spread by close contact rather than coughing and sneezing).

The differences between the SARS coronavirus and the MERS coronavirus highlight that, despite belonging to the same virus family, pathogens do not necessarily behave in the same way. It is as yet unknown whether the new virus is, or will turn out to be, more like SARS or MERS, or neither. 

Chinese authorities have confirmed that there is human-to-human transmission. However, it is not yet established whether it is sustained, which would make the outbreak more difficult to control. As of 23 January, the number of cases range from 500 confirmed cases up to an estimated 1,700 cases, according to a disease outbreak model by Imperial College London.

Likewise, we do not know to what extent the virus is able to mutate and if so, how rapidly. Generally, coronaviruses are known to be able to mutate, with the risk that a less contagious form of the virus becomes highly contagious. This could have an impact not only on the transmission pattern and rate but also the death rate. The virus could change in either direction, to become either more or less of a threat.

It is important to take a precautionary approach while uncertainty persists. It is also important not to overreact and for measures to be scientifically sound. Concern over this outbreak is due, but panic is not.

Three virtual networks of experts supporting the response – one of virologists, one of epidemiologists and one of clinicians – are working on the key pieces of the jigsaw puzzle: watching the virus, watching the transmission patterns, and watching the people who have been infected. It is crucial to maintain the ongoing investigation of the disease, stay focused on the science and to keep sharing the necessary information.