The outbreak of the 2019 novel coronavirus (2019-nCoV) infection has prompted a precautionary approach from Australian medical authorities but most people with the virus are experiencing mild disease according to the World Health Organization.
However about 20% of patients appear to progress to severe disease, including pneumonia, respiratory failure and in some cases death, a WHO situation report said.
“Clinical care of suspected patients with 2019-nCoV should focus on early recognition, immediate isolation (separation), implementation of appropriate infection prevention and control (IPC) measures and provision of optimized supportive care,” the WHO report recommended.
In Australia, there have been seven confirmed cases to date. Chief Medical Officer Professor Brendon Murphy has said there has been no local transmission of the virus and the concern is mostly for people returning from Hubei Province in China, where the outbreak started in Wuhan. A number of resources including information sheets for GPs and EDs are available on the Department of Health website.
Respiratory physician Professor Grant Waterer from the University of Western Australia told the limbic that respiratory physicians are unlikely to be inundated with affected patients and at present, coronavirus seems no worse and probably milder than seasonal influenza in its severity.
“Therefore I would expect the vast bulk to be dealt with in general practice but we will see some inpatients, especially those with pre-existing respiratory disease more vulnerable to respiratory decompensation.”
“In general most new viral infections tend to become less virulent over time with serial passage through human hosts with the worst outcomes in those infected when the virus first makes the jump from the animal source.”
While there were exceptions – notably the 1918 pandemic – there were few examples of new viral infections getting progressively worse over time, he said.
“…so it is exceedingly unlikely we are facing anything worse than the equivalent of an out of season influenza outbreak.”
Professor Waterer, who has a special interest in pulmonary infectious diseases, reiterated advice from the Chief Medical Officer that regularly hand washing was the most effective form of personal protection.
“Masks are good for cough hygiene, but won’t protect you from fomites on your hands.”
Early reports from China
A report on human-to-human transmission of 2019-nCoV in China, published in NEJM, found that the mean incubation period was 5.2 days, and in its early stages, the epidemic doubled in size every 7.4 days.
“With a mean serial interval of 7.5 days the basic reproductive number was estimated to be 2.2,” the report authors said.
In the Lancet the first report of clinical features in 41 patients admitted to hospital in Wuhan in December with 2019-nCoV infection showed that all were adults with an average age of 49 years and 73% male. Almost a third (32%) were admitted to ICU for high-flow nasal cannula or higher level oxygen support.
Patients with underlying cardiovascular disease and COPD were over-represented in the sub-group admitted to ICU compared to the whole group (23% v 15% CVD; 8% v 2% COPD).
“In this cohort, most patients presented with fever, dry cough, dyspnoea, and bilateral ground-glass opacities on chest CT scans. These features of 2019-nCoV infection bear some resemblance to SARS-CoV and MERS-CoV infections,” the study authors said.
“However, few patients with 2019-nCoV infection had prominent upper respiratory tract signs and symptoms (eg, rhinorrhoea, sneezing, or sore throat), indicating that the target cells might be located in the lower airway.”
The mortality rate in the cohort was high at 15%.
One of The Lancet Comment articles said deaths were often overrepresented in the early stages of emerging infections as “case detection was skewed towards the more severe cases”.
“Nevertheless, the 1918 influenza pandemic is estimated to have had a case-fatality ratio of less than 5% but had an enormous impact due to widespread transmission, so there is no room for complacency,” the authors said.