New study compels US and Britain to ramp up responses

A scientific paper on the new coronavirus published this week has been credited for influencing the British and American governments' response to the pandemic.

Following the report's advice, British Prime Minister Boris Johnson urgently imposed unprecedented peacetime measures on the population after earlier holding them off. American officials said the report also shaped the White House's response, prompting the authorities to strengthen their social distancing measures.

What did this scientific paper say that so compelled the authorities to act, and why was it so influential?

The paper, titled "Impact of non-pharmaceutical interventions to reduce Covid-19 mortality and healthcare demand", was published on Monday. The study was led by epidemiologist Neil Ferguson and compiled by 31 members of Imperial College London's Covid-19 response team.

Professor Ferguson advises the British government's Scientific Advisory Group for Emergencies, which is helping to coordinate the country's coronavirus response. Prof Ferguson said yesterday that he was in self-isolation after developing a dry cough and a fever.

The report referred to the Covid-19 disease as the most serious public health threat seen in a respiratory virus since the 1918 Spanish flu pandemic. The 1918 pandemic killed between 50 million and 100 million people around the world.

The researchers studied the potential effectiveness of several public health strategies to counter the virus, dividing their aims into two broad categories: mitigation and suppression. Mitigation focuses on slowing, but not necessarily stopping epidemic spread. Suppression aims to disrupt transmission so dramatically that each case generates less than one additional infection and the disease is stopped in its tracks.

They concluded that suppression was the "preferred policy option".

The major challenge of suppression, the British scientists concluded, is the length of time that intensive interventions would be needed, given that "we predict that transmission will quickly rebound if interventions are relaxed".

The authors said mitigation policies alone - isolating people suspected of having the virus at home, quarantining their contacts and separating the most vulnerable people from others - might reduce the peak demand on the healthcare system by two-thirds and deaths by half if applied for three months. But that would still result in hundreds of thousands of deaths and in health systems "overwhelmed, many times over", they said.

The researchers analysed data from Italy and China to mathematically model how the spread of the coronavirus would affect Britain and the United States in an uncontrolled social environment. The study predicted that 81 per cent of the British and American populations would be infected, with 510,000 deaths in Britain and 2.2 million in the US. The death rate was expected to peak after three months.

Prof Ferguson told BBC on Tuesday that there was no other way than to adopt the suppression strategy, and that it was becoming increasingly clear that the study's predicted death rate is "the most likely scenario".

A report in The New York Times has argued that it was probably not so much about what the report said but who was saying it. Imperial College London has ties to the World Health Organisation, and has advised the British government in several epidemics, including severe acute respiratory syndrome (Sars), avian flu and swine flu.