As the new coronavirus spreads and sickens more people in the USA, people with preexisting health conditions are at particular risk, public health officials say.

Actor Tom Hanks, who revealed that he was living with Type 2 diabetes in 2013, confirmed Wednesday that he and his wife tested positive for the coronavirus that causes COVID-19.

People with diabetes are among those at increased risk for complications from COVID-19, the Centers for Disease Control and Prevention says.

That's because fluctuations in blood glucose levels and possible diabetes complications can make it harder to treat a viral infection, the International Diabetes Federation says.

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Why someone with diabetes is at more risk for COVID-19

Though doctors are still learning what exactly puts someone at higher risk for developing a severe illness with COVID-19, early information indicates older patients and those with chronic medical conditions may be at higher risk.

According to early data from more than 44,000 confirmed cases in China as of Feb 11, deaths among patients who had diabetes were at 7%, compared with 0.9% for those without an underlying condition, the CDC says.

According to the International Diabetes Federation, there may be two reasons for the complications that can arise.

"Firstly, the immune system is compromised, making it harder to fight the virus and likely leading to a longer recovery period," the group wrote in its "Diabetes Voice" publication. "Secondly, the virus may thrive in an environment of elevated blood glucose."

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"Diabetes affects healing in general," said Dr. Susan Spratt, an endocrinologist at Duke University. Patients who have diabetes can have an increased risk of taking more time to heal and get a secondary infection, Spratt said.

People with diabetes can't make enough or can't as effectively use the insulin in their bodies, according to the CDC. Insulin helps people use sugar in their bloodstreams for energy. As the food we eat breaks down into sugar, or glucose, it is released into our blood, and our pancreas releases insulin to facilitate the process.

"When there isn’t enough insulin or cells stop responding to insulin, too much blood sugar stays in your bloodstream. Over time, that can cause serious health problems, such as heart disease, vision loss and kidney disease," the CDC says.

When a patient's diabetes is uncontrolled, meaning blood sugar levels are not in a recommended range, this can especially contribute to heart or kidney problems, said Dr. Maria Peña, director of endocrine services at Mount Sinai Doctors Forest Hills in New York.

Having both problems with their heart or kidney and diabetes could worsen the prognosis for patients with COVID-19, she said.

Another potential issue for patients with diabetes amid the COVID-19 outbreak is inflammation, said Peña.

Increased blood sugar can increase inflammation, as can viral infections, Peña said. With both increasing inflammation, this can increase the likelihood of a more severe complication, she added.

People with diabetes, even those with the condition well managed, are at a higher risk of complications from the flu as well, the CDC says.

Patients with Type 1 diabetes, caused when a person's immune system attacks the cells in their pancreas that create insulin, are at an increased risk for diabetic ketoacidosis. "This can make fluid and electrolyte management even trickier when trying to manage sepsis," Spratt said.

According to research published Wednesday in the medical journal The Lancet, sepsis and septic shock are among the severe complications observed in some COVID-19 cases.

What should people with diabetes do to prepare?

The CDC recommends people with preexisting conditions take everyday precautions to protect themselves from COVID-19. This includes avoiding contact with sick people, washing their hands regularly and not touching their face, among other measures.

Those who have a condition such as diabetes should make sure they're in contact with their doctor if they need extra medication or supplies, such as test strips or insulin.

The American Diabetes Association recommends gathering simple carbs such as regular soda, honey, jam, Jell-O, hard candies or popsicles.

"If you have diabetes and you have symptoms such as cough, high temperature and feeling short of breath, you need to monitor your blood sugar closely," Dan Howarth, head of care at Diabetes UK, said in a statement.

Follow USA TODAY's Ryan Miller on Twitter @RyanW_Miller