When it comes to social distancing, Josh Goldblum was ahead of the curve.

Diagnosed with leukemia in 2018, the 67-year-old Mount Airy lawyer underwent three rounds of chemotherapy, followed by a blood stem cell transplant in January 2019. The procedure left his body immuno-suppressed, unable to fight off infections. As a result, from the time he left the hospital in February until May he remained quarantined in his house, permitted to go outside but “not to be anyplace there was anyone else.”

“It stinks,” he said, recalling that period of isolation, a state now shared by millions due to COVID-19.

Although the COVID-19 virus can affect anyone, people who are immuno-compromised or considered “high risk” have an increased chance of hospitalization and landing in the ICU, according to the Centers for Disease Control and Prevention. Preliminary data released by the CDC late last month show that people with diabetes, chronic lung disease and cardiovascular disease — no matter their age — are particularly vulnerable.

The CDC report provides an early snapshot of cases in people already affected by other medical issues. Based on about 7,000 confirmed cases of COVID-19 across the U.S. in which health officials had a written record about the presence or absence of any underlying health conditions, the report shows that of people requiring admission to an ICU, 78% had at least one underlying medical problem. Of people hospitalized but not requiring ICU admission, 71% had at least one such condition, compared with 27% who didn’t need to be hospitalized.

Among the cases, 10.9% of patients had diabetes, 9.2% had chronic lung disease, and 9% had cardiovascular disease.

Other high-risk groups include people undergoing cancer treatment, bone marrow or organ transplants; those with immune deficiencies, poorly controlled AIDS or HIV; smokers, and patients with prolonged use of corticosteroid and other immune-weakening medications. Dialysis patients, people with liver disease, and those with severe obesity are also considered high risk.

It is not yet known whether the severity or level of control of underlying medical conditions affects the risk for severe disease associated with COVID-19, according to the report.

“Because COVID-19 is such a new disease, hard data is sadly lacking,” said Robert Fischer, an infectious-disease specialist at Einstein Medical Center. “It typically takes a year or two after an event like this before people can really collect data and study it analytically to form firm conclusions.”

But Fischer noted that if patients have another disease, it’s more likely that they will catch the virus and that their case might be more severe and make recovery more difficult.

Age can also prove a risk factor.

“Older people tend not to be as resilient and don’t have the reserve capacity to shrug off some kind of physiological insult,” Fischer said. “A 20-year-old with pneumonia may have trouble breathing for a week or two because their lungs are having a bit of difficulty oxygenating their blood. Maybe their heart has to pump a little harder. But if you’re 98 years old, your heart and lungs are probably working as hard as they can just to keep things running smoothly.”

The result?

“What is a mild pneumonia in a 20-year-old becomes a fatal illness in a 98-year-old,” he said.

A number of reasons make diabetes patients high risk if they contract the virus, said Mark Schutta, an endocrinologist at Penn Medicine.

“Even pretty well-controlled diabetics are immuno-compromised to a degree,” he said.

Schutta noted that if blood sugars rise above 200 even for a short period of time — which happens to most people with diabetes directly following a meal — it can disrupt the immune system’s ability to fight infections.

“In addition, simply having an infection can raise blood sugars and give rise to additional infections,” Schutta said. “And immunity can get disrupted by high blood sugars. It’s a circular problem.”

Although people in high-risk categories may want to improve their immune functions with supplements or a special diet, Fischer warned that the immune response to infections in incredibly complex.

“You can’t measure if your immune response is 90% of normal or 10% of normal," he said. "It’s not like taking your temperature,” he said.

Both doctors recommend that people with underlying illnesses carefully adhere to the CDC guidelines for social distancing and hand washing to avoid getting the disease in the first place.

“How the virus spreads is still not well-understood,” Fischer said. “The best thing we have now is to avoid contact with other people.”

Goldblum, whose cancer is well-regulated by medications, found that long walks in Valley Green and approaching social isolation one day at a time helped.

“You start looking over weeks and months, and it’s really hard to do,” he said. “The best thing is to try to take it day by day.”