How dangerous is the new coronavirus?
The fast spread of a new coronavirus in China has prompted global alarm, with neighboring states closing their borders, global airlines suspending flights, and some governments barring entry to foreign nationals who have recently been to the Asian country.
The rapidly spreading virus, which is thought to have originated in the central city of Wuhan in late December and has since been detected in more than two dozen countries, has infected at least 74,576 people and killed some 2,118 in mainland China. Two people in Hong Kong, one in the Philippines, three in Japan, one in France, one person in Taiwan, one person in South Korea, and two people in Iran have also died from the virus, known as COVID-19.
In a bid to limit its spread to countries with weak health systems, the World Health Organization (WHO), on January 30, declared the new outbreak a public health emergency of international concern.
A transmission electron microscopy image of the first isolated case of the coronavirus © Courtesy of IVDC/China CDC via GISAID/Reuters COVID-19 is transmitted much more readily between humans than its closest relation, Sars, which caused outbreaks of severe disease in a few countries in 2003. The new coronavirus is, however, less dangerous to most people it infects than Sars. Computer modeling suggests that each new COVID-19 case affects 2.5 other people on average when no effort is made to keep people apart. The Chinese authorities have significantly reduced this “reproduction number” through drastic action to isolate cases and trace their contacts — and the rest of the world is rapidly introducing social distancing measures. The virus has caused severe respiratory disease in about 20 percent of patients and killed more than 3 percent of confirmed cases. Sars shot 10 percent of infected individuals. Older people, whose immune defenses have declined with age, as well as those with underlying health conditions, are much more vulnerable than the young. But fatality rates are hard to estimate in the early stages of an epidemic and depend on the medical care given to patients. For example, ventilators save lives by enabling people with pneumonia to breathe. Most experts believe the current fatality rate is exaggerated by serious under-diagnosis of mild cases; the best current estimate is that COVID-19 will kill around 1 percent of those infected in a population with excellent healthcare. For comparison, seasonal flu has a mortality rate below 0.1 percent, but it affects so many people that it results in about 400,000 deaths a year worldwide. Spanish flu infected an estimated 500m people and killed 50m worldwide in 1918-19. Hypothetically, if COVID-19 affected half the world’s current population over a year with a 1 percent fatality rate, the death toll would be 35m — substantially increasing the number of deaths worldwide, which is around 60m for all causes in a typical year
