Also known as an index case, patient zero is a term used to describe the first human infected by a viral or bacterial disease in an outbreak. Advances in genetic analysis now make it possible to trace back the lineage of a virus through those it has infected. Combined with epidemiological studies, scientists can pinpoint individuals who may have been the first people to start spreading the disease and so trigger the outbreak.
Identifying who these people are can help address crucial questions about how, when and why it started. These can then help to prevent more people from getting infected now or in future outbreaks. Do we know who patient zero is in the Covid-19 coronavirus outbreak that started in China? The short answer is – no.
Chinese authorities originally reported that the first coronavirus case was on 31 December and many of the first cases of the pneumonia-like infection were immediately connected to a seafood and animal market in Wuhan, in the Hubei province.
This region is the epicentre of the outbreak, with almost 82% of the 75,000-plus cases registered so far in China and globally are from here, according to statistics complied by Johns Hopkins University. (Read more about the global fight against coronavirus.)
However, a study, by Chinese researchers published in the Lancet medical journal, claimed the first person to be diagnosed with Covid-19, was on 1 December 2019 (a lot of earlier) and that person had "no contact" with the Huanan Seafood Wholesale Market.
Wu Wenjuan, a senior doctor at Wuhan's Jinyintan Hospital and one of the authors of the study, told the BBC Chinese Service that the patient was an elderly man who suffered from Alzheimer's disease. "He (the patient) lived four or five buses away from the seafood market, and because he was sick he basically didn't go out,” Wu Wenjuan said.
She also said that three other people developed symptoms in the following days – two of whom had no exposure to Huanan either. However, the researchers also found that 27 people of a sample of 41 patients admitted to hospital in the early stages of the outbreak "had been exposed to the market".
The hypothesis that the outbreak started at the market and could have been transmitted from a living animal to a human host before spreading human-to-human is still considered the most likely, according to the World Health Organization (WHO).
(Blogger's notes: Some Chinese I know used to joke that one can't even fart in Communist China without local Party bosses knowing it. Is it believable that the Chinese Communist Party still does not know who and where the patient zero of the Wuhan Virus Outbreak is? Rumours and innuendos are the natural weapons of the oppressed to counter the blatant concealment and outright lies of the oppressive ruling class.)
Acknowledgements This work is supported by the National Natural Science Foundation of China (11772133, 11372116).
Declaration of interests: All authors declare no competing interests.