Is the coronavirus outbreak as bad as SARS or the 2009 influenza pandemic? A biologist explains the clues

The severity and mortality of a novel emerging virus, which we scientists in this case are calling 2019-nCoV, are very difficult to judge when new data are coming in on a daily basis. During the 2009 influenza pandemic, the earliest reports listed 59 deaths from approximately 850 suspected cases, which suggested an extremely high case fatality of 7%. However, the initially reported information of 850 cases was a gross underestimate. This was simply due to a much larger number of mild cases that did not report to any health system and were not counted. After several months – when pandemic data had been collected from many countries experiencing an epidemic wave – the 2009 influenza turned out to be much milder than was thought in the initial weeks. Its case fatality was lower than 0.1% and in line with other known human influenza viruses.