Coronaviruses: What We Know Now

This transcript has been edited for clarity.

This is Paul Auwaerter with Medscape Infectious Diseases, speaking from the Johns Hopkins University School of Medicine. The new year has brought a new infection to the landscape, and that is the novel coronavirus first described in December 2019 in Wuhan, China, where it caused respiratory illness and pneumonia.

As with any new infection, we are learning much about its epidemiology, the scope of illness, and impact on a day-to-day and week-to-week basis. It appears to be a member of the coronaviruses, which many of us have probably experienced as a cause of bronchitis or a common chest cold. But this family of viruses also includes those that have caused serious outbreaks (SARS and MERS, which is still ongoing sporadically in Middle Eastern countries), with fairly high mortality rates among those who are very ill and hospitalized.

Coronaviruses have often made the jump from circulating among animals to introducing new strains to humans, and it appears that this virus has done that. It was originally thought to be limited to people exposed to animals in Wuhan city, but it's very clear now that this virus can cause person-to-person transmission.

Initial indications from China were that it mainly afflicted elderly men, but deaths have now been described in relatively healthy younger people and also in healthcare workers. None of this is really surprising.

What We Know and What Remains Unclear

Exactly how severe the illness is and whether it might mutate remain unknown. It does seem, at least for those who are hospitalized, to have a lower mortality rate than SARS or MERS, perhaps under 5%. But realize that there may be people who do not seek medical care and have mild illness, so the mortality rate could honestly be much lower.

Unfortunately, there are currently no therapeutic interventions, even with MERS. Vaccines have been studied but none have been deployed yet. What we do know about it is that there can be up to a 14-day incubation period, with an average of about 8 days between being exposed to an index case and acquiring illness. Leukopenia (ie, a low white blood cell count) has been seen in patients who are more ill, and molecular diagnostic tests have already been developed.

Here in the United States, there have already been at least four cases as of the recording of this video. [Editor's note: The number as of the publication date is 5.] And there will probably be more, given what we know about this spread so far and the frequency of domestic and international travels that aid and abet such viral spread. I think the Centers for Disease Control and Prevention (CDC) has taken a prudent approach, asking anyone with travel to China to be screened (this has been carried out in airports), and patients with respiratory illness who come to the hospital or healthcare facilities are also being queried about recent travel. But that may not hold for very long if this is a more easily transmitted virus.

Lessons to Learn From MERS

There are lessons to learn from the MERS coronavirus, which led to a number of healthcare workers becoming ill early on. The key lesson is that promptly identifying patients and using respiratory droplet precautions and standard healthcare protections dramatically reduce the ability of the virus to be transmitted. CDC is recommending droplet contact precautions with airborne isolation if feasible. That's what we do for tuberculosis patients. Obviously, those types of rooms are relatively limited. I think that, as with MERS, droplet or contact precautions are probably sufficient.

This is the type of infection that I think any infectious disease physician is following with great interest. SARS sort of died out very quickly after a tremendous effort to follow patients, quarantine them, and prevent transmission. MERS is still ongoing sporadically in countries such as Saudi Arabia and others in the Middle East.

What will happen here remains unclear, but there are many coronaviruses circulating all the time, and it's unclear which side this particular one will fall on. I think many of us will be following this very carefully. Looking at the CDC page for frequent updates can help if you have any questions about testing protocols or how to handle patients who are suspected of illness. Thanks very much for listening.

Paul G. Auwaerter, MD, is a professor of medicine at the Johns Hopkins University School of Medicine and clinical director of the division of infectious diseases. His areas of clinical expertise include Lyme disease, Epstein-Barr virus, and fever of unknown origin. He has been a Medscape contributor since 2008.

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