Many patients with vaping illness also have stomach pain, nausea, vomiting and diarrhea, and it is important to ask people with those symptoms about vaping.

Doctors should “strongly consider” admitting patients to the hospital if they have become ill after vaping and are short of breath, have underlying illnesses that could affect their lungs or their blood oxygen level is less than 95 percent, the C.D.C. said. That level, called oxygen saturation, can be measured with a device clipped to the fingertip, the agency said in its Morbidity and Mortality Weekly Report, published on Friday.

The report also said that some patients who initially had mild symptoms then deteriorated rapidly within 48 hours. And many patients who ended up in the hospital had previously been sent home after seeking help at emergency rooms or clinics.

Because the vaping illnesses often involve severe inflammation in the lungs, many patients have been treated with corticosteroid drugs. But the report said it was not known whether the drugs really helped or whether the patients might have recovered on their own. And corticosteroids can increase the risk of infection.

The report says that “in some circumstances,” it might be best to avoid corticosteroids in patients who are being tested for illnesses like fungal pneumonia, which could worsen with the drugs. But the report also says that in patients who are severely ill, it may be necessary to give them corticosteroids along with other drugs to fight infection.

Patients who have had high doses of corticosteroids may need to see a specialist in endocrinology to help minimize or manage the side effects.

Patients older than 50 who become ill after vaping tend to be sicker than younger ones: more likely to need ventilators and to stay longer in the hospital. These older patients may need special consideration, the report said, adding that a quick diagnosis, treatment with steroids and consultation with specialists in pulmonary and critical care “might be lifesaving in this patient population.”