In a report released Thursday by the Centers for Disease Control and Prevention, DC health officials ratted out the first two known cases of hantavirus spillover in the city. The virus festers quietly in rats and other rodent populations, but in humans it can cause potentially deadly respiratory and hemorrhagic diseases. Humans pick up the infection by direct contact with rodent urine or nest dust or by breathing in aerosolized viral particles from urine, droppings, or saliva. There’s also the possibility that the virus can spread from rat bites, but this is less common. Once in a human, the virus almost never jumps from human to human.

Fortunately for DC residents, the type of hantavirus found in the city is one of the milder types: an “Old World” hantavirus called the Seoul virus. Old World hantaviruses cause a disease called Hemorrhagic fever with renal syndrome. HFRS can start out like a generic infection with fever, chills, nausea, and headache. But it can progress to low blood pressure, acute shock, vascular leakage, and acute kidney failure, the CDC notes. The severity of HFRS varies by which hantavirus you catch, but fatality rates can reach up to 15 percent. The Seoul virus is one of the milder forms, with a fatality rate of only about 1 percent. As such, in both of the cases reported by DC health officials, the infected individuals recovered.