In the two and a half weeks since Michigan confirmed its first case of coronavirus, it’s become one of the nation’s hot spots for COVID-19.

Michigan now has more cases than Illinois, more cases than Florida and three times as many cases as Ohio. The state ranks fifth behind New York, New Jersey, Washington state and Louisiana in confirmed cases per capita.

The situation is particularly dire in metro Detroit; only the New York and New Orleans metro areas have higher numbers when adjusted for population.

Almost 30% of Michigan’s COVID-19 cases are Detroit city residents and 83% involve residents of Wayne, Oakland or Macomb counties.

“Southeast Michigan is pretty much exploding with exponential growth of COVID patients, and hospital systems are being overwhelmed,” said Dr. Teena Chopra, an infectious diseases specialist for Detroit Medical Center.

“We’ve never seen anything like this before,” said Dr. Matthew Sims, infectious disease specialist for Beaumont Hospitals. “A large portion of the population is becoming infected. People are dealing with shortages of supplies and not really knowing what the best way to treat these patients.”

There are multiple theories about why the numbers have increased so quickly in Michigan, doubling every few days for the past week.

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No question, experts say, one factor has been an increased in testing. When Michigan confirmed its first COVID-19 cases on March 10, the state had only 300 coronavirus test kits and all the tests were being processed by the state Bureau of Laboratories.

Since then, the state has greatly expanded its test capabilities, with private labs and multiple hospitals -- including Beaumont and Henry Ford in metro Detroit and Sparrow in Lansing -- processing tests as well as the state Bureau of Laboratories.

But the rapidly rising numbers aren’t just a reflection of more testing, says Dr. Joneigh Khaldun, the state’s chief medical executive.

“I don’t think it’s just about we’re testing more people,” Khaldun told MLive. "There are more people getting sick in southeast Michigan from COVID-19.”

While increased testing helps explain the rising numbers, another critical factor is the susceptibility of the metro Detroit’s population to any infectious disease, said Chopra and Dr. Paul Kilgore, a medical doctor and epidemiologist at Wayne State University.

“Southeast Michigan and Detroit are a very vulnerable population with any infection. Flu, you name it, we always have a higher prevalence, so it’s not just about this pandemic," Chopra said.

“There’s a host of factors that make us more vulnerable,” she said. “You have a large number of older people with uncontrolled diabetes, with hypertension, with COPD. You have drug users and people who live in shelters.”

The high poverty rate in Detroit and some of the other surrounding communities means that people are less likely to seek medical attention unless they are very sick, Chopra said.

That high poverty rate also means people may not have heard about the state’s stay-at-home order or the social distancing guidelines, or may be less in position to adhere to them, Kilgore said.

“A really significant proportion of Detroiters have limited access to reliable health information,” because they lack Internet access and aren’t paying attention to the media, Kilgore said. "So a message of protecting yourself may not be getting out to people, and we don’t know what proportion of the population is not getting that message.

“People may be just going about their business as usual, not really understanding the potential impact of not only the behaviors on themselves, but on their family and people around them,” he said.

Even if they are aware of the guidelines, people in poverty who live in communal settings, rely on public transportation and/or have more limited access to running water, sanitizer and cleaning products may find it difficult to adhere the COVID-19 prevention protocols, he said.

Low-income residents also may be afraid to seek treatment if and when they do fall ill for fear of running up medical bills -- which can foster spread of COVID, he said.

The density of the metro Detroit population is yet another reason why the numbers are so high in southeast Michigan. Almost 40% of all Michigan residents live in Wayne, Oakland or Macomb counties.

“All the major metropolitan areas are beginning to see an explosion in numbers," Kilgore said.

Infectious disease thrives best in environments where people have a wide circle of social interactions and people are coming in and out of the community, maximizing the number of potential hosts, experts say. That makes areas such as metro Detroit much more susceptible than, say, rural communities where social interactions tend involve a much more limited number of people.

That leads to yet another theory of why metro Detroit has become a hotbed of coronavirus: Detroit Metro Airport was one of 13 in the country and one of only two in the Midwest along with Chicago’s O’Hare International Airport that have been serving flights from Europe and Asia during COVID-related travel restrictions.

Although those international travelers were screened as they arrived, it’s certainly possible that COVID patients who were asymptomatic went undetected and infected others as they headed out to domestic terminals for flights home, Kilgore said.

“There’s a good chance that some cases did come in" through the airport, he said.

Friday, the U.S. surgeon general said the situation in Detroit is likely to worsen over next week. That’s very likely true, Michigan health officials say.

“We’re on the up-slope right now, and we haven’t seen any sense that it’s flattening," Kilgore said.

But through strict adherence to the stay-at-home order and social distancing guidelines, he said, Michigan residents can help the state turn a corner on the coronavirus crisis.

“We can definitely flatten the curve; we can limit the number of people who get sick," he said.

“The No. 1 thing is staying home,”he said. “We need to get this message out to everyone, that you only go out to get food, get medicine, for essential reasons.

"Those are things that people can do that would really help and get to that flattening point as soon as possible.”

Read all of MLive’s coverage on the coronavirus at mlive.com/coronavirus.

Additional information is available at Michigan.gov/Coronavirus and CDC.gov/Coronavirus.

CORONAVIRUS PREVENTION TIPS

In addition to washing hands regularly and not touching your face, officials recommend practicing social distancing, assuming anyone may be carrying the virus. Health officials say you should be staying at least 6 feet away from others and working from home, if possible. Carry hand sanitizer with you, and use disinfecting wipes or disinfecting spray cleaners on frequently-touched surfaces in your home ( door handles, faucets, countertops ) and when you go into places like stores.

To read more on MLive:

Friday, March 27: Latest developments on coronavirus in Michigan

GM will build ventilators in Indiana, surgical masks in Warren

Whitmer says Michigan schools very unlikely to re-open this school year

Michigan medical chief fears hospitals will run out of room