Officials on Thursday announced an additional 15,152 cases of the new coronavirus after broadening their criteria for identifying new cases of the virus. The increase marks the largest single-day jump in cases since the outbreak was first reported.
Our analysis: The 'recurring themes' of disease outbreaks
About the outbreak
Reports of the new coronavirus first surfaced in early December 2019 in Wuhan, China. According to the World Health Organization (WHO), the main symptoms of the virus, which WHO on Tuesday officially named COVID-19, are fever and lesions in both lungs. Some patients also have reported difficulty breathing, WHO said.
On Thursday, health officials reported 15,152 new cases of the virus, bringing the total number of reported cases globally to more than 60,000. The vast majority of those cases have occurred in China, with most of the cases occurring in the Hubei province, which includes Wuhan. Officials on Thursday said 14,840 of the newly confirmed cases were in the Hubei province, bringing the total number of reported cases in the province to 48,206.
WHO on Thursday said there have been a total of 441 confirmed cases of the new virus reported in 24 countries outside of China. There have been 14 confirmed cases of the virus in the United States—including the latest case that CDC confirmed on Wednesday, which involves an American who was evacuated from Wuhan.
Officials said as of Thursday there have been at least 1,367 reported deaths linked to the virus. All but three of the deaths have occurred in mainland China, and 1,310 deaths occurred in the Hubei province.
According to USA Today, the latest data suggest the morality rate for COVID-19 is 2.3%. Data also suggest about 82% of COVID-19 cases—including all 14 cases confirmed in the United States—have been mild, and patients required little or no medical care, the Washington Post reports.
What caused the spike in reported cases?
Officials said the spike in reported cases mostly stemmed from the way officials in China's Hubei province are identifying new cases of the virus. Officials in the province now have begun reporting both confirmed cases and "clinical cases" of the virus, which include patients who exhibit all the symptoms of the virus but who either have not yet been tested or had a negative test for the virus, NPR's "Goats and Soda" reports. According to the Los Angeles Times, Hubei officials are considering clinical cases as confirmed based on patients' symptoms and a CT scan of patients' lungs.
Wang Chen, dean of the Chinese Academy of Medical Sciences, on Thursday said Hubei officials had to change requirements for confirming COVID-19 because of accuracy concerns about lab tests used to detect the new virus. He said, "Many patients who appeared to be [infected with COVID-19] based on their epidemiological history, contact history and clinical symptoms were not able to test positive on the nucleic acid test, and were listed as 'suspected cases.'"
Experts also said Hubei likely is experiencing a shortage of lab testing kits for the virus.
Hubei so far is the only province that has changed how it is reporting cases of the new virus, with other provinces in China reporting only cases confirmed by lab tests, "Goats and Soda" reports. According to the New York Times, Hubei's reporting change could help officials in deciding how to distribute resources and evaluate treatment options.
'A moving target'
However, some experts said the change could create confusion about how to diagnose COVID-19 and the outbreak's scale.
Peter Rabinowitz, co-director of the University of Washington MetaCenter for Pandemic Preparedness and Global Health Security, said, "It makes it really confusing right now if they're changing the whole way they screen and detect," and turns calculating cases of the virus into "a moving target."
According to the New York Times, experts noted that although it's common for scientists to change diagnostic requirements for new diseases as they learn more about them, it's difficult to make week-to-week comparisons about a pathogen's spread once those criteria have changed.
William Schaffner, an infectious disease specialist at Vanderbilt University, said, "It sounds simplistic, but it's so very important—what numbers are you counting?"
But other experts said the reporting change could provide a more accurate depiction of COVID-19's severity.
Matthew Frieman, a virologist at the University of Maryland School of Medicine, said data suggest COVID-19 is more akin to a "bad, heightened cold." He added, "[I]t's in the middle between SARS and the common cold," though he noted that shouldn't "diminish its importance."
Jennifer Nuzzo, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health's Center for Health Security, said the fact that most cases of the virus are mild could make it more challenging to contain, because "[m]ost of our surveillance is oriented around finding people who require medical intervention."
In addition, the Post reports that COVID-19 "can be quite severe" among older people and individuals with certain chronic conditions, such as diabetes, heart disease, and others.
Nuzzo said, "It could be that some people have an immune response that results in severe illness and some people don't," adding, "It is common … in coronaviruses that there is a spectrum of illness" (Su, Los Angeles Times, 2/13; Feng/Neuman, "Goats and Soda," NPR, 2/13; James/Stanglin, USA Today, 2/13; Caryn Rabin, New York Times, 2/13; Leng et al., Reuters, 2/13; Shih/Taylor, Washington Post, 2/13; Bernstein/Johnson, Washington Post, 2/12).