Covid-19: Five days that shaped the outbreak

By 30 December, several people had been admitted to hospitals in the central city of Wuhan, having fallen ill with high fever and pneumonia. The first known case was a man in his 70s who had fallen ill on 1 December. Many of those were connected to a sprawling live animal market, Huanan Seafood Market, and doctors had begun to suspect this wasn't regular pneumonia.

Samples from infected lungs had been sent to genetic sequencing companies to identify the cause of the disease, and preliminary results had indicated a novel coronavirus similar to Sars. The local health authorities and the country's Center for Disease Control (CDC) had already been notified, but nothing had been said to the public.

Although no-one knew it at the time, between 2,300 and 4,000 people were by now likely infected, according to a recent model by MOBS Lab at Northeastern University in Boston. The outbreak was also thought to be doubling in size every few days. Epidemiologists say that at this early part of an outbreak, each day and even each hour is critical.

Read more