The active impact of the new corona virus is very different in China, where tens of thousands of people are sick than in the rest of the world, with just a few dozen scattered cases. But data from both environments help scientists as they work to understand the virus and the disease it causes.
“With a large number of cases, you get a better idea of how the virus behaves on average in a community,” says Caitlin Rivers, senior associate at the Johns Hopkins Center for Health Security. “In a place with fewer cases, you can spend more time investigating each case.”
In the past week, researchers have published reports on large groups of coronavirus patients in China. One described how the disease affected 138 patients in Zhongnan Hospital at Wuhan University and discovered that about a quarter of them had to be cared for in intensive care and that some patients had atypical symptoms such as diarrhea and nausea. The study, published in the Journal of the American Medical Association, it turned out that hospital patients passed on the virus to 40 health professionals. Another team analyzed 1,099 patients from more than 500 hospitals in China. Of those, fever and cough were the most common symptoms and about 15 percent developed severe pneumonia. The data was that published as a preprint, has not yet been assessed by peers or published in a journal.
These studies and other studies give researchers a greater picture of the outbreak. “It tells us a lot about what happens when you have many overwhelmed hospitals,” says Angela Rasmussen, research scientist at the Center for Infection and Immunity at Columbia University Mailman School of Public Health. That helps public health officials in countries like the US prepare for what they can see if the virus continues to spread outside of China.
However, like all data from within an active epidemic, the information comes with some reservations: usually only the most serious cases of an illness come to the attention of the public health authorities and are admitted to hospital during an active crisis. So the cases included in these reports may be more extreme examples of illness.
Doctors in China are also focused on treating patients and stopping the spread of diseases, and they do not collect exhaustive data on individual cases. In places with just a few cases, such as the US, researchers have time to do more specific clinical evaluations of each patient.
“When you look at large groups, you sometimes miss some subtleties that you could investigate in one person,” says Rasmussen. “In a crisis situation, that type of data is often not collected because the priority is to care for people who are really ill.” ways a person could respond to an infection.
Individual case studies have their own limitations – no scientist would say they have conclusive evidence from just one data point – but detailed details about individual cases help them understand how infections unfold. A recent one case report about an American patient in Washington state, for example, a daily description of his symptoms and temperature. It also included all his laboratory results, such as his white blood cells and potassium counts. Another report, published this week, also followed the temperature of a Nepalese patient over time and contained images of his lungs.
With only a few patients to be treated, public health officials in countries without major outbreaks can also focus on tracking down anyone with whom a sick patient has come into contact. “In theory you could find all new infections,” says Rivers. The Centers for Disease Control and Prevention (CDC), for example, keeps a close eye on the close contacts of all American cases and records new symptoms and tests them for the virus if necessary. This helps to understand how the virus is transmitted from person to person and how many additional people infect sick patients.
These anecdotal case reports and epidemiological studies of large groups are costly for researchers because they are trying to learn how dangerous the new coronavirus is, says Rasmussen. “All different studies are important.”