Wuhan coronavirus: Human-to-human transmission in China started as early as mid-December, says new study
Human-to-human coronavirus transmission among close contacts took off much earlier than thought, say scientists who studied the first 425 infected Wuhan patients.
This new evidence adds to the growing uncertainty over the Wuhan coronavirus. The new findings, published in the New England Journal of Medicine, suggest that coronavirus began spreading between closely-related people from the middle of December, while Chinese authorities had confirmed this on January 20, almost a month later. Another Lancet study indicated that human-to-human transmission in China began on January 2.
"Although the majority of the earliest cases were linked to the Huanan Seafood Wholesale Market and the patients could have been infected through zoonotic or environmental exposures, it is now clear that human-to-human transmission has been occurring and that the epidemic has been gradually growing in recent weeks," write scientists in the study.
Wuhan — a large city of 11 million people in central China — has been in the news since December 31, when China alerted the World Health Organization (WHO) of a pneumonia-like illness circulating in the city.
Since then, the number of infected patients has increased, even overtaking the SARS outbreak. Currently, the virus has sickened over 9,692 people and killed 213 others. By comparison, SARS infected 8,422 people. Still, the virus continues to remain a mystery.
What does the study say?
The new study tries to provide answers to one such mystery: the nature of the virus and how it transfers between people.
So the team of scientists collected data from 425 patients after interviewing infected patients and those who have interacted with them, including relatives, close contacts, and health care workers.
During the interview, the team asked these participants to recall when they fell sick, their visits to clinical facilities and subsequent hospitalizations if any. The team also gathered information about possible contact with others showing similar symptoms, all of which were then vetted.
The Wuhan coronavirus cases have been doubling in size approximately every 7.4 days in Wuhan at this stage. "Human-to-human transmission among close contacts has occurred since the middle of December and spread out gradually within a month after that," say the researchers.
From the analysis of the 425 patients, the team found that children were less likely to contract the infection and if they did, the children showed milder symptoms. It is notable that few of the early cases occurred in children, and almost half the 425 cases seemed to appear in adults over 60 years or older, explain the authors of the study.
Their analysis found that on average each patient has been spreading the infection to 2.2 other people, which falls in the range estimated by others and the WHO. However, others have come up with different estimates, with some estimating that one infected person can spread the infection to 3.5 other people or more. By comparison, SARS was estimated to be around 3.
These findings could uncover more mysteries of the virus. "Our findings provide important parameters for further analyses, including evaluations of the impact of control measures and predictions of the future spread of infection," write the authors.