For the first time, a person in the US has died of complications related to the Zika virus, CNBC reports. Puerto Rico's health secretary announced today that a 70-year-old man with Zika died in February from severe thrombocytopenia, a condition of the blood that can lead to internal bleeding.

For adults, dying from the Zika virus is unusual. In most cases, the virus — which can be transmitted through mosquito bites or sexual contact — isn't dangerous. Only one out of every five people who are infected develop symptoms, which are similar to the flu and last no more than a week. There’s no vaccine or treatment for Zika, however, and that's concerning. Two weeks ago, the CDC confirmed what had long been suspected: the Zika virus cause birth defects, including microcephaly — a condition that causes children to be born with abnormally small heads. Zika has also been linked to Guillain-Barré Syndrome, a severe neurological disorder that can lead to temporary paralysis in people of all ages.

So far, 570 people have become infected with the Zika virus while in the Puerto Rico, which is a US territory. In the US states, 426 cases of Zika have been recorded, but all involved people who acquired the virus while traveling abroad.