Novel coronavirus – comment from David Murdoch

Professor David Murdoch, Dean and Head of Campus, University of Otago, Christchurch, comments:

"There are still many gaps in our knowledge about this novel coronavirus and, like everywhere else in the world, we are learning more each day about the virus and the infection it causes. Although there is still a lot we don’t know about the virus, the broad context of this outbreak is one with which we have some familiarity. Existing knowledge about similar viruses and their behaviour help us a lot.

"Respiratory viruses typically cause illnesses ranging from the common cold at the milder end of the spectrum through to infection of the lung tissue itself (pneumonia), which can be life-threatening. We are still working out where the novel coronavirus fits on this spectrum. Some coronaviruses that we encounter every year rarely cause anything more than the common cold, while SARS and MERS coronaviruses were responsible for outbreaks that caused pneumonia in a relatively high proportion of cases.

"An early report from China on 41 people admitted to hospital with novel coronavirus infection indicated that all had pneumonia and one third had other underlying medical problems. However, it is important to note that this report only includes cases who were unwell enough to be admitted to hospital. It is also important to bear in mind that we tend to hear more about the most severe cases in the early stages of a new disease, as these are the cases first brought to our attention. We still do not know the full spectrum of disease, including what proportion of those infected have mild or no symptoms at all.

"The proportion of cases who die is one marker of disease severity, and the information we have to date indicates that the known case fatality associated with infection with the novel coronavirus (~2% with current data) is less than with the SARS epidemic in 2002-2003. We still do not know why some people die from this new infection and some people do not. In general, those with more severe disease caused by respiratory viruses tend to be people with underlying medical problems and/or with impaired immune systems.

"Other critical information that helps develop prevention and control plans include an understanding of how easily the virus is transmitted between humans, the duration of transmission in humans, the mode of transmission, and potential sources of infection.

"Early information is that between 1.5 and 3.5 people will be typically infected by each case - similar to influenza, but much less than measles. There have also been reports of potential transmission while a case was without symptoms, but this has yet to be substantiated. Based on our understanding of the evolution and natural history of other respiratory viruses, including SARS and MERS, there is every expectation of non-human animal sources of infection, and we are already starting to hear speculation in this regard.

"While these details are becoming known and with greater certainty, public health authorities are justified in taken a cautious approach to prevention and control strategies, and have the challenge of making big decisions in the face of key knowledge gaps and rapidly changing information."

No conflict of interest.