Since returning to campus from break last month, an unusually large number of students have fallen victim to colds and the flu, students and a University Health Services nurse said this week.

A UHS nurse practitioner in Student Medicine said she has noticed a rapid increase in illness, particularly the flu, sweeping through residential colleges since January. While some students speculated that recent cold weather may have weakened Elis’ immune systems, the nurse said undergraduates’ close quarters and tendency to share possessions are responsible for most college epidemics.

“After the break, we did see a lot of gastrointestinal viral systems,” she said. “A lot of these illnesses come from living in close quarters, sharing food, sharing water bottles.”

The nurse said many of cases of colds and flu could be avoided if students stopped sharing their possessions, such as bottles and towels. Sports teams tend to share towels frequently, she said, which can help spread germs at a rapid rate.

The most likely cause for the spike in stomach flu is students forgetting to wash their hands, the nurse said. After students touch communal desks and doorknobs on their way to and from classes, she said, the most important thing they can do to stay healthy is wash their hands every time they eat or even touch their mouth.

“People don’t wash their hands nearly enough or keep their rooms clean,” Josh Colon ’10 said. “Obviously that’s going to make it really easy for germs to spread.”

Colon said he was sick for about three days at the beginning of February.

Dylan Stern ’08 said he succumbed to the stomach flu last Friday and tried to nurse himself back to health with a starchy diet of bread, rice and water. For a day or two, Stern said, he and his suitemates were focused on germs — and avoiding them — until he recuperated and the immediate threat of sickness disappeared.

Stern said that trying to stay warm and running from building to building all day might take its toll on students’ immune systems.

“You expend so much energy going out in the cold and trying to stay warm,” Stern said. “I’m physically exhausted at night when I get back to my room, a lot more than normal.”

But some students said they do not see the number of illnesses so far this semester as anything out of the ordinary.

Ben Barasch ’09 said he was sick with the flu, but has not heard of a great number of illnesses. He said he was only sick for a day, and, although it was unpleasant, it was nothing more than a normal winter bug.

Still, the nurse said that even though these bugs might be common for this time of year, it is important to take special precautions. Especially with the stomach flu, she said, students should go to the doctor if there is any concern about dehydration. Student Medicine provides IV fluid in the infirmary to avoid dehydration from the flu.