Health officials in Tennessee are now reporting 10 cases of suspected respiratory disease among people who used electronic cigarettes or other vaping devices.
State epidemiologist Tim Jones said in a statement that Tennessee health care providers are reporting any patients treated for severe respiratory symptoms who have reported vaping in the weeks before they became ill.
Tennessee's health department says the Centers for Disease Control and Prevention and U.S. Food and Drug Administration are investigating a cluster of severe pulmonary disease among people who use e-cigarettes or vaping products. Officials say 450 cases have been reported in 33 states.
According to the CDC, six people have died as a result in the states of California, Illinois, Indiana, Kansas, Minnesota and Oregon.
Patients have shown symptoms including cough, shortness of breath and chest pain. Other symptoms may include fever, fatigue, nausea, vomiting and diarrhea. Most cases are seen among adolescents and young adults.
As the CDC, FDA and state health officials investigate, they caution that no one single linking cause or substance has been identified within all the cases -- just that patients reported using e-cigarettes in some form in all the reported cases of respiratory illnesses.
As agencies work to identify more information about the products used, where they were obtained, and what substances were contained within them, the CDC and FDA are warning people to take a few precautions.
While they've explicitly said they have not determined one substance to be a cause for the illnesses yet, the FDA said in a consumer update people should avoid THC vaping products, as many people reported using THC vaping products before experiencing respiratory illness. Most of those THC samples also contained high levels of Vitamin E acetate, according to the FDA.
"Identifying any compounds that are present in the samples will be one piece of the puzzle but will not necessarily answer questions about what is causing these illnesses," the FDA said.
Both the CDC and FDA also said people should avoid any vaping products bought on the street. Regardless of the investigation, both agencies said teens, young adults, pregnant women, and adults who do not currently use tobacco products should not used e-cigarettes.