President Donald Trump was ready to play doctor when asked about reports of a possible outbreak of pneumonic plague in Russia on Monday.

Though Russian officials have yet to confirm what caused the death of a 28-year-old employee of a Siberian plague research lab, the president said Russia might have a “big problem” on its hands.

Appearing to mix up common pneumonia with the aggressive lung infection known as pneumonic plague, Trump told reporters, “It’s a rough disease. You know, that’s a disease we used to be able to control, but somehow, those microbes have got stronger and smarter. They’re like an army.”

Continuing to share his medical theory, Trump said, “The germs have really become relatively stronger than they were, and things that used to work on pneumonia don’t work as well anymore.”

Still, the president sounded confident about his diagnosis, despite saying he had yet to speak with Russian President Vladimir Putin about the possible outbreak.

Two hundred people are currently under medical observation after a woman who worked at a disease research center died of a “pneumonia of undetermined origin” last week, per local authorities.

According to local reports cited by Axios, the woman broke a test tube containing the pneumonic plague pathogen before falling ill and dying days later.

Pneumonic plague is nearly 100% fatal if antibiotics are not administered within 24 hours from the onset of symptoms, which typically appear within one to three days of exposure. Symptoms include fever, headache, weakness, shortness of breath, chest pain, coughs and bloody or watery mucus.

Though the disease is serious and information about the potential outbreak is still scant, a U.S. health official who spoke to The Washington Post said, “It’s in Siberia. Unless someone gets on a plane and gets to the U.S., it is low risk. We should be alert but not panicked.”