The coronavirus spreading through China has affected nearly 8,000 people worldwide and killed more than 100—and scientists are racing to find out just how contagious and deadly the disease actually is.
About the new coronavirus
Reports of the new coronavirus first surfaced in early December 2019 among people in Wuhan, China. According to the World Health Organization (WHO), the main symptoms of the virus, called 2019-nCoV, are fever and lesions in both lungs. Some patients also have reported difficulty breathing, WHO said.
Officials in China said there have been 170 reported deaths, all occurring in China, linked to the virus. As of Wednesday, Chinese officials and the World Health Organization had reported 7,711 confirmed cases of the virus. Reported cases involve patients in Australia, Cambodia, Canada, China, France, Germany, Japan, Korea, Macau, Malaysia, Nepal, Singapore, South Korea, Sri Lanka, Taiwan, Thailand, Vietnam, and the United States. In the United States, officials have confirmed five cases of the new coronavirus, and CDC is monitoring at least 110 people across 26 states for possible infection.
How contagious is the virus?
One key area of focus for scientists seeking to contain the virus is understanding how contagious the disease is. To do that scientists use the disease's R0, or "R naught," Vox reports. An R0 shows the average number of people someone infected with the disease could likely infect. A higher R0 represents a more contagious disease—and anything above a one means the disease "can cause sustained transmission in humans" since its R0 is above one, according to Maia Majumder, from Boston Children's Hospital.
For example, measles, which is the most contagious virus known, can have an R0 as high as 18 if the exposed people aren't vaccinated, Vox reports. Meanwhile Ebola, which is much less contagious, typically has an R0 of two.
It's important to note that R0 is not "something that is fixed," according to Marion Koopmans, head of the department of virology at Erasmus Medical Center, as diseases often act different in different environments and some people are more contagious than others.
WHO estimated that a person infected with the new coronavirus has spread the virus to between 1.4 to 2.5 other people on average, giving it an R0 that is less than SARS' R0 of three, but higher than that of the seasonal flu, which has an R0 of 1.3, Vox reports.
Other estimates from epidemiological modeling labs, such as the one at Boston Children's or the University of Bern in Switzerland, estimate the R0 of the new coronavirus to be between two and 3.8, meaning the virus could potentially be more contagious than SARS.
How deadly is the virus?
Another key question scientists are trying to answer is how deadly is the disease? To determine that, researchers need to calculate its case fatality rate (CFR), meaning the number of deaths within a certain group of people with the disease, Vox reports.
The problem is, to get a good grasp on the CFR, researchers need to know how many people in a certain population have the virus and how many of those people die, two things that are often unknown at the early stages of outbreaks, Vox reports.
To get an accurate CFR for the new coronavirus, scientists would need to survey the Chinese people to determine who has antibodies for the coronavirus, according to Majumder. The task would also entail counting those who were asymptomatic.
"Until we've done [that]—and I'm sure it'll happen sometime in the future—there are going to be some people that have mild infections or are asymptomatic infections that we're not picking up," Majumder said.
As a result, it will be some time before we have an accurate idea of how many people have been infected by the virus and how many people have died from it.
HHS Secretary Alex Azar has said the virus is a "potentially very serious public health threat" but added that Americans "should not worry for their own safety right now."
Similarly, CDC has said that "the immediate health risk of this new virus to the general public is low in our nation."
All of which means that "you're probably more likely to be catching flu than you are to be getting coronavirus," according to Devi Sridhar, chair of global public health at the University of Edinburgh in Scotland (Belluz, Vox, 1/28; Hernandez, Roll Call, 1/28; Kenen, Politico, 1/28; Sheikh/Thomas, New York Times, 1/28; Sun/Bernstein, Washington Post, 1/28; New York Times, 1/30).