The scientists who designed the models say they rely on such hard data as positive and negative test results and death rates in this country and others. They consider such things as scientific studies that detail the properties of the virus.
However, people’s behavior also has a big effect on the computer models’ predictions.
In an effort to slow the spread of the disease COVID-19, Gov. Larry Hogan issued a stay-at-home order March 30. On social media, some Marylanders have announced they’re taking steps to “flatten the curve" by social distancing and wearing face masks.
The state may be seeing signs that those efforts are working, but it’s still too early to know for sure, Dr. Thomas Inglesby, director of the Johns Hopkins Center for Health Security, said during a news conference Tuesday.
Here what you need to know about the predictions for Maryland:
How does social distancing affect the predictions?
Without a vaccine or a therapy to stop COVID-19, the only way to prevent the disease from spreading is through social distancing measures, Inglesby said.
One person with COVID-19 can on average infect two to three others.
“New generations of cases could occur every five to seven days without social distancing measures,” Inglesby said.
If the virus was left to spread without social distancing, then the number of sick people, especially the critically ill, could overwhelm the state’s health care system, he said.
“If our health systems were to become overwhelmed, the mortality of this virus would go sharply up and hospitals would have a difficult time providing medical care," he said.
What do the predictions say this week?
The Institute for Health Metrics and Evaluation at the University of Washington said a peak in hospital use could come in late April. That would be just after a projected national peak in mid-April.
Earlier this week, the Washington model projected Maryland would have 1,766 deaths by Aug. 4, but that prediction has since worsened, anticipating 2,326 deaths. The model also said it could range from 1,400 to 4,136.
It projected more than 81,766 deaths nationwide by the same date, with a possible range of about 49,400 to 136,400.
When should we expect the peak?
Maryland health officials were hopeful Tuesday that the state is nearing its peak. One model used by the White House has it occurring about 10 days from now. Other models show it coming a bit later.
Still, Inglesby said, models are only best estimates and don’t necessarily take into account how seriously Maryland has put social distancing measures in place.
In the 24 hours preceding the news conference at which he spoke, Maryland had seen lower numbers of new cases and hospitalizations, Inglesby said.
“It’s only one day of data, but if confirmed over time, it would be a very good move in the right direction," he said.
Dr. Leana Wen, a former Baltimore City health commissioner and now a George Washington University professor, said it is difficult to predict the degree and duration of the disease’s peak when the number of coronavirus infections is unknown.
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A lack of widespread testing in the U.S. has officials estimating where the virus trajectory is headed.
“Not all patients with symptoms are even being tested. Many people are self-isolating at home,” Wen said. “And there are likely many more, even tens of thousands more, who have mild or no symptoms and don’t know they have COVID-19.”
What happens when the number of cases finally decreases?
A peak also doesn’t mean the pandemic is over or state directives can be lifted.
“Once we’re able to bring cases down to smaller numbers in our state, it will be time to consider how to begin to ease social distancing," Inglesby said.
He called for equipment for health care workers, increased health department staffing and technology to help track and isolate cases, and expanded diagnostics so that even the mildest forms of COVID-19 cases can be detected on the same day.