Gov. Gretchen Whitmer spoke directly to young Michiganders on Monday as she announced an executive order requiring people to stay home to avoid spreading novel coronavirus.

"Young people, I'm talking to you now," Whitmer said. "You're not immune from this. You can get this virus. ... You can carry this without even knowing it and be unknowingly exposing others to it.

"There's been this misperception that if you're young, ... you're not susceptible to COVID-19. The fact of the matter is in America, we are seeing severe consequences in our younger people in ways that they haven't seen it in other parts of the world."

She speculated that vaping might be a contributing factor. Of the people in Michigan with confirmed cases of the virus, 41% are ages 20-49, according to data from the Michigan Department of Health and Human Services. Despite a spate of vaping-related lung injuries nationally in 2019, the habit is popular among young people.

"I've talked to more than one physician who has observed, and perhaps there's too little science to know precisely if this is what's going on, but vaping is a lot more popular in the United States than it is elsewhere," Whitmer said. "And that ... compromises your respiratory system and makes you more susceptible to respiratory illness."

Dr. Samuel Allen, a pulmonologist at Beaumont Health, told the Free Press that it's too soon to say what role vaping is playing in the global coronavirus pandemic, which, as of Monday night, had infected about 375,000 people and killed at least 16,400, according to the Johns Hopkins COVID-19 Global Case Tracker.

"There's really no scientific evidence that links the two," he said. "First of all, it's because vaping itself is relatively still in its infancy. So is it plausible as a kind of an interesting observation? Yeah. But as far as a scientific link, there's none."

But, Allen said, a person who has lung injury from vaping probably would be more likely to be severely sickened by COVID-19 than someone without vaping-related lung injury, just as a cigarette smoker, someone with chronic lung disease, diabetes, immune suppression or heart disease would.

Dr. Meilan Han, a pulmonary specialist at Michigan Medicine and professor at the University of Michigan, said that while most of the research about the novel coronavirus suggests older people are more likely to be hospitalized and die of the disease, "we certainly do know that there are young people in the United States that clearly are experiencing severe disease and are on ventilators.

"And so people have been hypothesizing as to what some of the risk factors might be. We don't have a lot of published data from the U.S., so we're looking to the little bits of published data that are coming out of China.

"What they're seeing is that one of the risk factors ... does appear to be smoking."

One report suggests that smokers have a 14-times higher risk of severe illness with a COVID-19 infection than nonsmokers, she said.

"We don't have a lot of data on vaping right now, but there is reason to potentially hypothesize that things that cause lung inflammation like smoking, like vaping might increase the risk for more severe disease," she said.

Dr. Arnold Monto, professor of epidemiology and global public health at the University of Michigan, said any connection to vaping and the rate of young people with severe disease from COVID-19 is speculation.

"There's vaping," he said. "Young people have gotten sick. Maybe it's vaping, but we don't have a link. What we would want from an epidemiologic standpoint is to have the histories of those who became sick and see whether they vaped. But there's no data that I know of, so it's pure speculation."

Whitmer's stay home, stay safe order also addressed the potential that the number of novel coronavirus cases could overwhelm the health care system as it spreads "exponentially" through the state.

More:These essential Michigan businesses can remain open during 'Stay Home' order

More:Henry Ford's lab is first in Michigan to begin processing same-day coronavirus samples

The death count in Michigan was up to 15 Monday afternoon, and the state's total confirmed case count reached 1,328. Whitmer predicted the number of confirmed COVID-19 cases could rise fivefold more over the next week.

"We have roughly 10 million people in our state," she said. "There is a model that anticipates and if we stay on our current trajectory, just like Italy, over 70% of our people can get infected with COVID-19.

"Of that 7 million people projected, about a million of them would need to be hospitalized. Let me give you a little perspective here. We have about 25,000 acute care beds in Michigan. ... Without additional aggressive measures soon, our hospitals will be overwhelmed. And we don't currently ... have enough beds, masks, gowns and ventilators.

"But if we all do our part and simply stay home, we have a shot at helping our health care system meet our needs. Because this disease can't spread person-to-person if we're not out there."

The model Whitmer referenced is a worst-case scenario, Monto said.

"I think you have to be prepared for the worst and hope for the best," he said, adding that how Michigan — and the country fares — in the days and weeks ahead depends on several factors.

"It all depends on how many people have already been sheltering in place as much as they could," Monto said, and how many heed the governor's warning and take her order seriously going forward.

"A lot of this is dependent on human behavior and those who like to go out and party are still going to go out and party," he said. "Short-term, the less contact we have with others who might be infected is the best policy."

Additionally, Monto said, how quickly the disease spreads in a region also can be affected by what he called "super spreaders" or people who happen to shed more of the virus than others.

"There's many things we don't understand," he said. "What we do know about this virus is that it's much less uniform in terms of how much an individual case will spread to another case," he said. "... We have super spreaders. We have anecdotes of people who don't spread, even though they're potentially infectious, and we really do not understand this."

Even with most people complying with the shelter-in-place order, Monto said it's hard to predict how the U.S. will fare in this outbreak.

"It's very hard to model that because everything in the modeling ... assumes some kind of uniformity."

Han said she is concerned that the rapid spread of the virus could affect not just the amount of available hospital beds, ventilators, COVID-19 test kits and personal protective gear like masks and gowns, but also of doctors, nurses and other trained medical personnel who can treat the sick.

"If you look at Italy, Han said, "roughly 10% of their COVID patients are health care workers. And that is what we are absolutely trying to avoid.

"The supply chain strain on the personal protective equipment and the testing swabs is real. I haven't talked to a single hospital that isn't experiencing some strain on the supply, and everyone's in some various state of numbering the days or weeks of supply that they actually have left."

Although President Donald Trump announced the federal government is distributing supplies of ventilators and personal protective equipment to states, he said the priority is to give the most to the states that have the biggest outbreaks.

"That's California, New York and Seattle," Han said. "But that doesn't mean we don't need it here at home.

"We worry because it we're not getting prioritized currently on the national front. We know that we don't have the demand yet, but we could be New York in a week, so it definitely has everyone worried.

"I'm definitely not trying to panic people. I've spent a lot of time talking to my own patients trying to reassure them, that if they take precautionary measures, do what the governor says stay at home, wash their hands, continue to isolate, I think we can get through this.

"But if people just continue to go about their daily business, nobody gets a pass on this."

Contact Free Press health reporter Kristen Jordan Shamus: 313-222-5997 or kshamus@freepress.com. Follow her on Twitter @kristenshamus.