A Chinese study, claiming that an incubation period of the new coronavirus (COVID-19) could be as long as 24 days, lacked scientific evidence, experts said.
A Chinese research team, led by Zhong Nan-shan at Guangzhou Institute of Respiratory Health, released a report, titled “Clinical characteristics of 2019 novel coronavirus infection in China,” on the medical journal on-line site, medRxiv. The report claimed that the incubation period of the new coronavirus could be as long as 24 days, with the median incubation period at three days.
The research team analyzed the data of 1,099 confirmed patients at 552 hospitals in 31 provinces/provincial municipalities and found that only 1.18 percent of the patients had direct contact with wildlife. Thirty-one percent had been to Wuhan, and 71.8 percent had contact with people from Wuhan.
The patients’ most common symptoms were fever (87.9 percent) and cough (67.7 percent). Only 43.8 percent showed fever during a medical examination. Diarrhea (3.7 percent) and vomit (5 percent) were uncommon.
However, Korean experts of infectious diseases said the study lacked evidence to change the incubation period of the new coronavirus, which is set at 14 days.
Kim Woo-joo, a professor of the Infectious Disease Department at Korea University Guro Hospital, said people should pay attention to the median incubation period at three days.
“If we line up the 1,099 patients who participated in the study, we can say that the median incubation period for the 550th patient is three days. Many of the patients had a short latent period,” Kim said. “Saying the incubation could last for 24 days is a significant deviation from the median.”
Most of the patients’ incubation periods were between zero and 14 days, and only a small number of patients had a 24-day latent period, he noted.
“The paper did not elaborate on this part. Patients who had a 24-day incubation period could have contacted other patients. So, there should be a thorough epidemiological study to find the exact incubation period,” Kim added.
However, he pointed out that only 80 percent of the Chinese patients had fever and cough and that some Korean confirmed patients had cough only, without fever. Thus, physicians should not exempt patients from the new coronavirus test just because they do not show fever, he said.
The Korea Centers for Disease Control and Prevention (KCDC) also said there was no reason to change the incubation period, although it belatedly confirmed the 28th patient.
Some critics said the recent Chinese report and the late diagnosis of the 28th patient, who was an acquaintance of the third patient, might signal that the new coronavirus could be latent for a maximum of 24 days instead of 14 days.
However, the KCDC brushed off such a possibility.
The KCDC said as the 28th patient had been taking anti-inflammatory painkillers regardless of the new coronavirus, the patient might have missed symptoms of the new coronavirus.
A single report is not enough to change the incubation period, the agency added.
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