Detailed research just published by the Chinese Centre for Disease Control (CCDC) into the first 44,600 confirmed cases of Covid-19 in China gives us our first solid indication of how lethal and how infectious the novel virus might be.
Some 81 per cent of cases were mild, with a clear majority (86 per cent) of confirmed cases occurring in people from 30-79. About 14 per cent of patients had a severe illness including those with pneumonia, while some 5 per cent became critically ill, with respiratory failure, septic shock, and multi-organ failure.
The overall case fatality rate was 2.3 per cent; most of those who died were over 60 or had underlying medical conditions such as heart disease, diabetes or chronic respiratory problems. For people over 80, the death rate was almost 15 per cent. And there have been relatively few cases of the illness in children.
While the authors estimate that the epidemic peaked between January 23rd and 26th, this conclusion has been challenged by the World Health Organisation (WHO).
Director general Tedros Adhanom Ghebreyesus said the report’s indication of a fall in cases should be interpreted with caution.
“Trends can change as new populations are affected,” he said. “It’s too early to tell if this reported decline will continue. Every scenario is still on the table.”
So what can we say with any certainty about the new coronavirus in the light of the latest data? It is about 20 times deadlier than the regular seasonal flu. But it is less lethal than previous coronaviruses like Mers- CoV, which kills about 35 per cent of people who become infected, and Sars, which killed about 10 per cent.
How easily can the new coronavirus spread from person to person? Data is less complete on infectivity, but it is estimated that each person with the new bug could infect somewhere between 1.5 and 3.5 people. In comparison, people with influenza tend to infect, on average, 1.3 others.
Disease severity and infectiousness are some of the key indicators of how extensive an infectious disease outbreak will be. A high severity and low transmissibility is the “ideal” combination that works towards limiting how long an epidemic will last. The indication so far is that Covid-19 has lower severity and a roughly similar infectiousness to Sars.
How these factors, and containment efforts, play out in the coming weeks will determine the global health and economic effects of Covid-19.
