Perhaps you’ve wondered why everything is getting canceled when 54 people have died from the coronavirus in the United States as of Saturday night, according to the Johns Hopkins Coronavirus Resource Center, compared to an estimated 34,200 deaths from influenza last flu season, according to the Centers for Disease Control and Prevention.

Perhaps you’ve thought that “the media” is overreacting or creating hysteria.

Or if neither of those statements applies, you’ve surely heard them expressed by a friend or family member, or on social media or in a comments section online.

What scientists know about the differences between COVID-19 and the flu, how the virus spread in China, and hospital capacity — along with what they don’t know — explain why government officials and private entities have taken such drastic measures.

The response is not just about what’s already happened, but also about what public health and medical experts forecast will happen.

Biostatistics researchers at the University of Massachusetts Amherst have conducted four weekly surveys of infectious disease modeling researchers, and the 21 experts surveyed March 9-10 believe nationwide hospitalizations won’t peak until May.

Overall, the experts believe that only 13% of all COVID-19 infections were reported to the CDC as of March 9. Their answers ranged from 4% to 30%, implying there were between 1,410 and 10,575 undiagnosed infections across the U.S. at the beginning of last week.

“We are anticipating a sudden spike in the numbers of people who need significant medical intervention,” said Jennifer Muggeo, deputy director of Ledge Light Health District in New London, on Friday.

She pointed out a few ways the coronavirus differs from the flu: The number of cases that can result from one COVID-19 case is higher than those that would result from one flu case, and the percentage of people who will require critical care is higher.

A person with the flu tends to infect 1.3 others on average, whereas the World Health Organization and other teams of researchers estimate the “replication rate,” or R0, is 2.3 for the coronavirus.

The World Health Organization said the global death rate among confirmed cases of the coronavirus so far is 3.7%, though many experts believe the true mortality rate is lower, given that people without serious symptoms aren’t being tested.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases since 1984, testified before Congress on Wednesday that he estimates the true rate to be “somewhere around 1%, which means it is 10 times more lethal than the seasonal flu.”

Cornell University infectious disease expert Gary Whittaker told The Washington Post that the length of time it takes one infection to lead to another is faster for the flu, meaning it’s practically impossible to contain the flu through social distancing.

And, of course, there’s a vaccine for the flu, while there isn’t one for the coronavirus.

Flattening the curve

Dr. William Horgan, regional director of quality and safety for Hartford HealthCare and a Groton resident, spoke in a succinct video posted Wednesday to “give everybody a bit more of a basis on why we’re reacting the way we’re reacting.”

He said the U.S. has about 100,000 intensive care unit beds, and on any given day 65,000 are filled, leaving 35,000 to handle newcomers to the ICU.

“That’s our trauma patients, that’s our critically ill patients that need it after having a stroke, after having a heart attack, dealing with cancer,” Horgan said. Hospitals are accustomed to dealing with an influenza outbreak every winter so they can plan for it, but now they need to accommodate COVID-19 patients on top of flu patients.

“Can we deal with 1 million cases within a 1-month period of time in the U.S.? Probably not. That stretches our capability and our capacity to deliver care to the limits,” Horgan said. “If we had that 1 million cases over a 4-month period of time, yes, we should be able to deal with that.”

That’s why people keep talking about, and showing diagrams of, “flattening the curve.”

The idea is that event cancellations and social distancing will spread out cases over time, causing the peak in the bell curve of cases to happen within hospital capacity — or at least, as not as far above capacity as if there were no interventions.

“It’s about limiting the number of people who have a need for that level of medical intervention,” Muggeo said.

Ledge Light Director of Health Steve Mansfield questioned what would happen if 10 people needed to be intubated but Lawrence + Memorial Hospital only had the personnel and supplies for five.

What we know, and what we don’t

According to Organisation for Economic Co-operation and Development data from 2016 to 2018, the U.S. has fewer overall hospital beds per 1,000 people than other countries that have been harder hit so far by the coronavirus: 2.8, compared to 3 in Spain, 3.2 in Italy, 4.3 in China, 6 in France, 8 in Germany, and 12.3 in Korea.

Ken Thorpe, deputy assistant secretary for health policy during the Clinton administration and now a professor of health policy at Emory University, told The Day on Saturday that innovation in medicine has meant more care being moved to the outpatient side, meaning there’s been a dramatic reduction in hospital beds since the 1980s. He also said that for COVID-19, other countries have probably done a better job on the testing side.

A study published in The Lancet on Jan. 31 estimated that the number of cases in Wuhan, China, doubled every 6.4 days.

To succeed in preventing large epidemics outside Wuhan, the study’s authors said “substantial, even draconian measures that limit population mobility should be seriously and immediately considered in affected areas, as should strategies to drastically reduce within-population contact rates through cancellation of mass gatherings, school closures, and instituting work-from-home arrangements.”

In a study published earlier this month, researchers from Harvard University, Johns Hopkins, and Nanjing Medical University in China compared Wuhan, where strict disease control measures were implemented six weeks after sustained local transmission, with Guangzhou, where measures were implemented within a week of case importation.

They found that COVID-19 accounted for a total of 32,486 ICU days in Wuhan from Jan. 10 to Feb. 29, and 318 from Jan. 24 to Feb. 29 in Guangzhou, a city with a larger population.

The authors said that contact rates in Wuhan during the early phase may have been much higher than what is expected in the U.S. because of Lunar New Year celebrations in Wuhan. But they also said that “hospitalization and ICU needs from COVID-19 patients alone may exceed current capacity” in a U.S. city.

“The actual number of hospital and ICU beds that will be needed over the course of a COVID-19 outbreak in a US city is impossible to estimate precisely,” they said.

Tom Frieden, a former CDC director, highlighted a table of scenarios with a mortality rate ranging from 0.1% to 1% and an infection rate from 0.1% of the population to 50%; this creates a range of possible deaths in the U.S. from 327 to more than 1.6 million.

He told The Washington Post, “Anyone who says that they know where this is going with confidence doesn’t know enough about it.’

As for southeastern Connecticut, Mansfield said mid-day Friday, “We know there are cases in our jurisdiction. We just don’t have the test results back.”

Within a few hours, he confirmed a COVID-19 case for a Rhode Island child attending a preschool in Mystic.

For a list of the latest closures in the region, visit bit.ly/CVclose.

 e.moser@theday.com