Coronavirus is not under control in much of the US, according to a report from scientists at Imperial College London, who warn that relaxing the lockdowns further now could result in another surge in deaths.
Around half of all states still have reproduction rates above one, the report warns, meaning that each coronavirus patient is infecting more than one other. Any reproduction rate above one means the virus spreads exponentially.
The findings come as almost every state and territory in the US has begun to ease restrictions on movement, despite many not having hit the milestones set by the US Centers for Disease Control and Prevention for doing so. Robert Redfield, the head of the US Centers for Disease Control and Prevention, told the Financial Times this week that he expected a second wave of cases this winter.
Axel Gandy, professor of mathematics at Imperial, said: “What this shows is that the epidemic has not passed. The numbers have come down, and the efforts are showing results. But continuous efforts are needed.”
The report estimated the reproduction rate in each of the 50 states, based on the number of reported deaths and mobility statistics as measured by Google. It found that in half of those, the rate is probably above one, with the highest rates recorded in states including Texas, Arizona and Colorado.
The Imperial model is being used by New York to track the virus’ spread across the state. It shows that New York, which has been hit harder by the disease than any other state, initially had a reproduction rate around five, but is now significantly below one.
It also models what would happen to the daily death rates in different parts of the country should people return to anything like normal patterns of behaviour.
A return to 40 per cent of previous mobility, for example, would mean deaths in New York would most likely return to the previous peak of about 1,000 a day and could jump as high as 3,000. The same could happen in Florida, the report warns, where the previous peak was around 80 deaths per day.
Mr Gandy said however that those numbers could lower if people’s behaviour changed while travelling, for example by wearing masks, keeping their distance from other travellers and washing their hands frequently.
But he added: “It could be a very significant mistake if you relax too much. We need to keep the R-number under one, and at the moment it seems most states are not very far below that.”
The findings will bolster the warnings being made by many public scientists in the US about the loosening of restrictions.
Speaking last week to members of Congress, Anthony Fauci, one of the most senior scientists on the White House coronavirus task force, warned of “suffering and deaths” if the states relaxed their curbs too quickly.
Donald Trump, the US president, however, has been pushing state governors to begin reopening their economies as soon as possible, with most beginning to follow suit. Oklahoma, for example, has reopened its nightclubs; Florida has reopened its gyms.
Mr Trump has hit out at the warnings being made by his own administration’s health experts, saying for example that Dr Fauci’s admonitions showed he was trying to “play all sides”.
Nevertheless, Mr Redfield has said he expects another wave of US infections later this year as the virus is reimported from the southern hemisphere.