New data from the Chinese COVID-19 epidemic reveal important clues as to how the outbreak unfolded – and how it is subsiding earlier than expected.
Bruce Aylward, a Canadian physician and epidemiologist, led the World Health Organization's COVID-19 mission to China. This week, he showed reporters epidemic curves, or epicurves, of the Chinese outbreak COVID-19 to illustrate how the chains of transmission – people who spread the infection to others – were stopped.
An epicurve is a graph that shows the frequency of new cases over time based on new infections per day. In many cases, an epicurve follows the curve of a bell, constantly rising to a peak and then decreasing as the outbreak burns when the virus runs out of people susceptible to infection.
For epidemiologists – scientists who study diseases in populations – the curve shape reflects the source of the outbreak: it would vary according to the existence of a single common source, such as contaminated food or multiple sources of infection as sick people in the general public.
China data showed that the increase was halted.
"What you see is that this is going up and suddenly it is dull," said Aylward. This is an image that suggests that some kind of measure was taken to mitigate the outbreak, which the team estimated in China between January 23 and February 2.
"It is a unanimous assessment by the team that they changed the course of this outbreak. It was a rapidly escalating outbreak. It hit the plateau and is falling earlier than expected," said Aylward.
The report was released in English on Friday.
"When you look at the difference between what the curve may have looked like and what it really looks like, it probably represents hundreds of thousands of Chinese who have benefited from this tremendous effort."
China's unprecedented measures to stop the respiratory pathogen included outdated public health tools that Aylward said were applied "vigorously":
- Find infected people and track their contacts, as family members.
- Quickly hospitalize those who were seriously ill.
- Restrict movements by closing schools and businesses, suspending public transport and banning mass meetings – measures that have also been described as draconian.
"We are at the highest level of alertness and the highest in terms of dissemination and impact. But this is not to alarm or scare people," said Dr. Mike Ryan, executive director of the WHO emergency program.
"People need to do a reality check now and really understand a government, a society-wide approach is needed," Ryan told reporters on Friday.
WHO officials said the biggest lesson of their mission in China: speed is everything.
Dr. Maria Van Kerkove, technical leader of the WHO emergency program, joined Aylward's mission in China. She gave other examples where the containment approach has worked so far: Singapore, Vietnam and Nepal.
"These are examples of where countries have managed to contain this," Van Kerkove said in a press interview on Friday. "But the point is that … the sooner we act and with what intensity, especially in the initial cases, they will determine whether you are dealing with multiple cases, one case or a small cluster, or if you are dealing with hundreds or thousands."
In China, Aylward said, officials are not letting their guard down and are continuing to build hospitals and buy fans, should the virus reoccur as blockages are eased.