Coronavirus outbreak: Death rate likely overestimated as many infected are yet to be diagnosed, say experts
While scientists are still trying to figure out how bad the new coronavirus outbreak will be, experts now say the current death rate might have been overestimated.
Experts reason that many more people are likely to have been infected by the virus, but not suffered severe enough symptoms to go to a hospital, and so have not been counted. Further, there could be cases that are yet to be confirmed as tests are being conducted.
During a media briefing on February 4, China’s National Health Commission said the national mortality rate is 2.1% of confirmed cases. Judging from the analysis of death cases, Chinese experts said the national mortality rate was stable currently. It was 2.3% at the beginning of the epidemic, “which can be said to have decreased slightly,” they added.
Dr Amesh Adalja, a senior scholar at the Johns Hopkins University Center for Health Security, estimates that the current fatality rate — the percentage of people with the new coronavirus who die from it — is 1%.
“In an outbreak, you really have to interpret fatality rates with a very skeptical eye, because often it’s only the very severe cases that are coming to people’s attention. It’s very hard to say those numbers represent anything like the true burden of infection,” Adalja told Reuters.
Several people told Reuters that in Wuhan, some patients with milder symptoms have been turned away from hospitals in recent weeks because of the strain on resources, while others have decided to self-isolate.
According to the latest figures released by China’s National Health Commission, there have been 563 deaths in China and 28,018 reports of confirmed cases within the country.
“There still remained 24,702 suspected cases. 26,302 patients were being quarantined for treatment (including 3,859 in serious condition). So far, 282,813 people have been identified as having had close contact with infected patients. 186,354 are now under medical observation,” they said.
As on February 4, the case fatality rate of confirmed cases in Hubei Province was 3.1%, while in the epicenter — Wuhan — it was 4.9%.
“The cumulative number of confirmed cases of pneumonia of the new type of coronavirus infection nationwide was 20,438 (calculated according to the mortality rate of confirmed cases, as of 24:00 on February 3), and the cumulative death rate was 425. Based on this figure, the national mortality rate is 2.1% of confirmed cases,” said Chinese medical experts, according to a statement released by the Commission.
“The fatality rate in other provinces is 0.16%. Therefore, from this group of figures, we can see that the main death is still in Hubei, and it is mainly concentrated in Wuhan. For other provinces in the country, although the number of cases is not small, the case fatality rate is actually quite low. From this point of view, we are still confident that most of our cases are still mild cases, so there is no need to panic,” the statement read.
Explaining why the fatality rate in Wuhan was so much higher than in other provinces across the country, the Chinese experts said early-stage critically ill patients were mainly admitted to three designated hospitals, where there was a shortage of resources, with just 110 critical care beds. The rest of the country was also grappling with shortages in beds, protective equipment, among others, which are being addressed. Based on the measures being taken, the experts said that it will "not take long for this effect to show up, and the fatality rate in Wuhan should gradually decrease.”
Officials also said that while the absolute number of fever outpatients in Wuhan is increasing, the growth rate has slowed in the recent period.
Dr Tom Inglesby, director of the Johns Hopkins Center for Health Security, also expects the case fatality rate to drop. He explained that in every outbreak like this, the most serious cases get recognized first. They are the ones that are sickest in the hospital, including people who die from the illness.
“There is always going to be a skew toward seeing those people first. But we know, at least from past outbreaks — and we have every reason to believe in this outbreak—that there is a wide range of illnesses and that in this case, the majority of people who are infected with this novel coronavirus seem to have mild illness and full recovery. It is a small fraction of the people who are getting severe or critical illness or dying from it,” said Inglesby, an expert in infectious disease, pandemics and public health preparedness.
He added, “And we know during every new outbreak, over time we're going to see much milder or even completely asymptomatic cases as part of the larger tally. And what that will do is it will show us that the case fatality rate will likely be much lower.”
Inglesby explained that while on the one hand, it is alarming to have case numbers go up, on the other hand, when more with the illness are diagnosed, there is a broader understanding of the range of severity. “We may also learn that for an increasing number of people, it is not a life-threatening illness. That's the hope, and there's a scientific rationale for believing that,” he added.
Inglesby said most disease modelers are not modeling too far out beyond a short period of time — a week or two weeks — because there is a lot of unpredictability given the lack of data.
“The other thing that scientists are reluctant to model is the overall case fatality rate. When things really settle out or become clear, there's a widely shared view that the case fatality rate will continue to come down, but how far it comes down, people aren't yet ready to say,” he said.