The Hunt for Patient Zero in Covid—19 has suggested that the original source of the outbreak was not the Huanan Seafood Market in Wuhan, China, in December, and now researchers are trying to identify the real source of the infection.
In fact, documents have suggested the earliest case of covid-19 may have been a 55-year-old person from Hubei province who seems to have contracted the virus on 17 November.
The first cases to be flagged, in December, were reported by Wuhan doctors using a surveillance protocol designed to pick up pneumonias with unknown causes. The system was set up after the 2002-2003 SARS outbreak, to detect new viruses.
Following this, New Scientist understands that early efforts by Chinese authorities to identify covid-19 cases focused only on people with viral pneumonia who had traceable links or contact with the Huanan market.
This focus on pneumonia may mean that many milder early cases were missed. By December, infections had probably already spread outside Wuhan. A study of six children who contracted the covid-19 virus identified a girl who developed symptoms on 2 January (NEJM, doi.org/ggpxpr). She and her family live in Yangxin, more than 150 kilometres from Wuhan. None of them had travelled outside the county for a month before she became ill, and the researchers weren’t able to identify how she became infected.
One explanation for this could be that the virus has jumped into humans from animals several times. Bats are thought to be the reservoir of the covid-19 virus but a more probable scenario is that other animals may have acted as intermediaries, amplifying the virus and enabling it to infect multiple humans in a method of trial and error.
Identifying the source of the outbreak is crucial, given that three coronaviruses – the SARS, MERS and covid-19 viruses – have all emerged since 2002. “In evolutionary terms, that’s in microseconds,” says Richard Kock at the Royal Veterinary College in London. “The risk of these things happening has enormously accelerated. We have to get a grip on that.”