In many parts of the United States, the arrival of the robin means that spring has sprung.

But for health science professionals, this bird has come to symbolize something else … West Nile virus. That’s an infectious disease native to tropical parts of Africa, Asia and Australia. It first appeared in the U.S. in 1999 and quickly spread across the country.

West Nile is transmitted by mosquitoes, and primarily affects birds. However, it can also be passed to humans. Between 1999 and 2010, an estimated 1.8 million U-S citizens were infected with West Nile. And more than thirteen-hundred of them died. The victims are often older people and those with compromised immune systems.

Here’s where the robins come in: They’re a favorite type of prey for Asian tiger mosquitoes and other species that transmit West Nile.

The virus can be ejected through a female mosquito’s mouthparts when she feeds. Once infected, a bird can pass along the pathogen to other mosquitoes that feed on it. And if the pests bite people afterward, they may transmit the virus.

A review article in the journal Science looked at the role robins have played in the spread of West Nile in North America. The authors concluded that robins are disproportionately responsible for West Nile cases in the U.S., compared with other bird species.

One reason for this is that robins survive remarkably well in areas where people live and work. So, if you’re accustomed to seeing red-breasted robins in the springtime, do yourself a favor: Wear insect repellent, long pants and long-sleeved shirts when you head for the great outdoors. Because getting bitten by mosquitoes is unpleasant at best.

And, for some people, warding off these blood-sucking pests could mean the difference between life and death.