States with the most cases include Wisconsin, with 15 confirmed cases and 15 more under investigation. Illinois has 10 confirmed cases, while 12 more are under investigation. California is looking into 19 such cases. The New York State Department of Health said Friday it was "actively investigating" 11 cases. Indiana and New Jersey both reported nine cases, of which Indiana has confirmed six.
Health officials in Connecticut, Florida, Iowa, Michigan, Minnesota, North Carolina, Pennsylvania, Texas and Utah also said they were aware of confirmed or potential cases. A total of 42 states and Washington, DC, provided CNN with a response.
Health officials in multiple states said it was unclear whether there was a connection between cases or whether vaping definitely caused these illnesses – which led to multiple people being hospitalized.
A tough condition to track
The Minnesota Department of Health reported this week that some patients were hospitalized for "multiple weeks," in some cases ending up in the intensive care unit. They came with symptoms including shortness of breath, fever, cough, vomiting, diarrhea, headache, dizziness and chest pain.
They are also tricky to track, experts say, because vaping-related lung disease is not a mandatory condition to report. Some health departments said they would not track this data.
"There is no diagnostic code … for vaping related lung diseases. So it will be difficult to track and track," said Dr. Humberto Choi, a pulmonologist and critical care specialist at the Cleveland Clinic.
Choi said he has seen three cases himself over the last several months – and he suspects there were others who did not think of vaping as a potential cause.
"People had the impression that vaping was something safe," Choi said. "They don't connect new symptoms with vaping."
Choi's state of Ohio, however, is not one of the states where health departments are currently reporting cases, according to the state's health department.
"It's hard to tell what to expect in these cases because it's something new," Choi said.
No clear culprit
The lung disease initially looked like it was caused by an infection, "but every test has come back completely negative," he added.
Wisconsin's cases were largely in the southeastern part of the state, Haupt said. This borders the northeastern part of Illinois, where the state's initial patients were hospitalized.
While officials are still trying to determine which products patients use, some states – including Wisconsin, Minnesota and New York – said use of both nicotine and marijuana products had been reported.
CNN's Nadia Kounang, Minali Nigam, Jen Christensen, Amanda Watts and Sheena Jones contributed to this report.