How long will Americans be fighting the coronavirus?
WASHINGTON (AP) — In a matter of days, millions of Americans have seen their lives upended by measures to curb the spread of the new coronavirus.
Normally bustling streets are deserted as families hunker down in their homes. Many of those who do venture out try to stay a safe distance from anyone they encounter, even as they line up to buy now-precious commodities like hand sanitizer. Parents juggle childcare as schools close, perhaps for the rest of the school year. And restaurants and bars sit empty as more and more convert to delivery-only options.
How long will this last? Scientists say there isn’t a simple answer.
“In many ways, this situation is unprecedented – we’re trying to take some actions to curb the spread and timing of this pandemic,” said Stephen Morse, a disease researcher at Columbia University in New York.
Yes, there have been past disease outbreaks that scientists can draw some lessons from but, in those cases, the disease was largely allowed to run its course. "So those models don’t precisely apply,” Morse said.
On Monday, President Donald Trump said the U.S. may be managing the outbreak through July or August. And New York Governor Andrew Cuomo said the state’s number of coronavirus cases may peak – not end – in 45 days.
The overall message is that the country will be fighting the virus outbreak for a matter of months, at least, not days or weeks.
Each model of how the disease could spread relies on data and assumptions about population dynamics, demographics, health care capacity and other factors, said Rebecca Katz, a public health expert at Georgetown University.
The challenge for designing models of what will happen next in the U.S. is that limited testing for COVID-19 means researchers don't know what the starting point is — how many people are already infected.
In simplest terms, scientists say that the epidemic will slow when people with infections don't pass the virus on to others.
“Basically, if I infect one other person or more ... then the epidemic can take off. If I infect less than one person and everybody infects less than one person, then the epidemic will decline," said Elizabeth Halloran, a disease researcher at the University of Washington.
Based on data from China and from cruise ships, scientists estimate that unless measures are taken to limit the spread, each infected person will infect about 2 or 3 others, leading to an exponential growth of the virus.
If the virus makes a jump to new person every two to five days, as scientists calculate, then a single infected person could lead to 4,142 total infections within a month — assuming nothing is done to break chains of transmission.
Unless such measures are put in place, scientists estimate that between 40 and 80% of the global population could become infected. Based on an analysis of data from China, scientists found that the majority of new infections are transmitted by people with mild symptoms who may not even know they're ill, said Jeffrey Shaman, a public health expert at Columbia University.
Even if most people recover and only a fraction of total infections are severe enough to require hospitalization — about 14%, scientists estimate — the sheer scale of the epidemic will put enormous strain on hospitals, healthcare workers and other patients who may see unrelated procedures delayed.