‘Tip of the iceberg:’ Why Covid-19 deaths will keep rising even as the coronavirus outbreak wanes
As signs emerge that China’s coronavirus outbreak may be moderating, a morbid reminder of the disease’s toll is expected to persist, or even rise, in the days to come.
While new cases reported in China appeared to decline after a Feb. 4 peak, the number of dead has grown to around a hundred a day — double the daily count of just a few weeks ago.
But those deaths aren’t a sign the virus is getting more deadly, according to experts.
“Deaths are a lagging indicator,” said Marc Lipsitch, an epidemiologist at Harvard University, who is modeling the outbreak. Once people are infected, “it takes around three weeks on average for someone to die.”
On Thursday, the Hubei province where the outbreak is centered issued a revised count of cases and deaths, using a new methodology. The new method adds 13,332 new cases and 135 deaths to the total in the province — infections that were diagnosed using medical imaging but not a lab test.
Across China, more than 1,300 people have died from the virus and more than 59,000 have been infected, according to authorities. Outside experts have said the number of cases is likely far higher, and Hubei’s announcement that it was counting thousands of new cases in its total will likely add to that analysis.
As of Wednesday, there were 8,204 patients classified as severe cases, according to numbers released by Chinese officials. New confirmed cases have fallen to about 2,000 a day, down from a peak more than 3,500 daily cases last week.
“If cases only plateaued a week ago, we might expect numbers of new deaths to continue to rise for some time yet,” said Steven Riley, professor of infectious disease dynamics at Imperial College London’s MRC Centre for Global Infectious Disease Analysis.
The chaotic nature of the outbreak combined with limited access by international experts to Hubei province, where it began, has made it hard to know the full extent of the epidemic. Bloomberg and other news outlets have reported on a health-care system overwhelmed by the disease, with some severe patients turned away and sent home — making a final count of deaths far more difficult.
“It may be by far that the vast majority of people are those who died at home,” said Michael Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota’s medical school. “We may never know how many people have died from this disease in China. I don’t think we ever will.”
Health experts have been working to estimate the deadliness of the disease. A crude analysis done by dividing the number of deaths by the number of confirmed cases yields a mortality rate of about 2%. Other estimates that attempt to account for undiagnosed, milder cases have put it closer to 1%.
“It’s dropping every day as the number of tested patients is going up,” Soumya Swaminathan, chief scientist of the World Health Organization, said in an interview.
Making matters more confusing, the crude mortality rate mixes together a wide variety of disparate populations.
“We are seeing the tip of the iceberg, and it is a very large iceberg,” said Harvard’s Lipsitch.
There are people who were hospitalized for other conditions in Wuhan and who then acquired the infection from coronavirus patients in the same facility. The numbers also include severe cases in Hubei province and other parts of China who were diagnosed early, precisely because of the gravity of their illness. And there is a large swath of healthier patients with mild cases, who are more likely to recover but less likely to ever be diagnosed.
“You are seeing case fatality rates in different populations being glommed together,” said David Fisman, an infectious disease doctor at the University of Toronto. The coronavirus death rate in vulnerable patients may not be relevant to healthy people who get the virus through everyday contact, he said.
While many people want to compare the outbreak to SARS, a coronavirus outbreak from 2002 and 2003 that infected more than 8,000 people and killed almost 800, a better comparison is seasonal influenza, said Anthony Fauci, head of the NIH’s National Institute of Allergy and Infectious Diseases.
Seasonal flu kills about 0.1% of those infected, while pandemics in 1957 and 1968 had mortality rates closer to 1%. The catastrophic 1918 contagion, known as the Spanish flu, had a 2% mortality rate, similar to what’s seen now in Chinese hospitals, Fauci said.
“It’s very different from influenza, but it would be acting like a really bad influenza season,” he said.
The uncertainly about how nasty the virus will turn out to be is a problem for public health officials trying to prepare for its potential spread around the world.
The death rate “is a number that we really can’t nail down at the moment,” said Ian Mackay, a virologist at the University of Queensland in Australia. “It is hard because we need that number to know how much to prepare.”
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