Texas health officials said Tuesday that a patient diagnosed with monkeypox died in what may be the nation’s first-known fatality from the virus.

The patient was an adult with a severely compromised immune system who lived in the Houston area, health officials said. The case is under investigation to determine what role monkeypox played in the individual’s death, officials said.

“Monkeypox is a serious disease, particularly for those with weakened immune systems,” said Dr. John Hellerstedt, the Texas state health commissioner. “We continue to urge people to seek treatment if they have been exposed to monkeypox or have symptoms consistent with the disease.”