In a press briefing in Geneva, WHO Director-General Tedros Adhanom Ghebreyesus told reporters of the higher mortality estimate based on reports coming in from around the world, according to an article on CNBC.com. Novel coronavirus causes the disease COVID-19.

The estimate of COVID-19's higher mortality estimate represents a significant escalation of the health risk posed in the event that coronavirus infections spread significantly. Concern about the coronavirus outbreak has already resulted in the cancellation or postponement of public events scheduled for March, such as the American Physical Society meeting in Denver.

By point of comparison, the mortality rate from the seasonal influenza virus is around 0.1% in the U.S., according to published sources.

In the press briefing, WHO officials said that much of the difficulty in estimating the health impact of the novel coronavirus comes from the fact that the virus behaves differently from the flu virus, and the mechanisms by which it is transmitted aren't fully understood, according to the CNBC report.

On the positive side, they said that in countries that have put in place "strong measures" to contain outbreaks, virus transmission can be suppressed.