The recent norovirus outbreak on local college campuses appears to be winding down, but it may not be over yet. Public health officials note that an outbreak may take several weeks to wane and that the numbers of cases will fluctuate from week to week.

“We continue to work closely with the State Health Department, Mercer County Division of Health, Princeton University, and Rider University (Westminster Choir College),” said Princeton Health Officer David Henry. “In addition, my two inspectors have been advising retail food establishments of the importance of keeping food handlers home if they have diarrhea or vomiting, and urging employees to wash their hands frequently with soap and water. Hand sanitizer has little or no effect on the norovirus. We are also in close contact with local schools (public and private).”

“The cases being seen at the health center have declined and they are now very close to the average number that are usually seen at this time of the year,” said Princeton University spokesperson Martin A. Mbugua. Since January 29 [through Monday, February 27], he said, about 269 students with symptoms of gastroenteritis have been seen at the McCosh Health Center.

Mr. Henry confirmed the University’s account. “Within the past five days, the number of students seen at McCosh Health Center with GI symptoms has dropped to three to five students a day. Last Thursday, they only saw two students. Their baseline number for students with gastrointestinal symptoms averaged two a day in February 2011, so they are currently approaching baseline numbers for gastrointestinal symptoms.”

Only two additional cases of norovirus were reported over this last weekend at Rider, where the total number among students on both campuses [Lawrenceville and Westminster Choir College, in Princeton] as of February 27 was 219, according to a Rider update released at the beginning of this week.

The College of New Jersey was less specific. A recent article in the school’s paper, The Signal, reported that while “some students have been experiencing norovirus-like symptoms,” an accurate determination could not be made because “all of the students” who reported symptoms declined to have a stool test. “Without a stool test, Health Services can only identify these students as having a gastrointestinal illness,” rather than actually having norovirus, the article noted.

Rutgers, the State University of New Jersey with campuses in Camden, Newark, and New Brunswick, appears to be relatively unaffected so far. “The university has received only a small group of students with positive flu tests at the health services,” reported Executive Director Melodee Lasky. “When compared with previous years, the number is lower than expected.” Outside the state, however, new cases have been reported at George Washington (85 cases) and Howard Universities, both in Washington, D.C.

At the local elementary-high school level, the norovirus alert that recently appeared on the Princeton Regional School District’s website remains on the front page, albeit further down. Princeton Country Day School’s website simply has a cautionary “message from Nurse Carol” providing a link to the Centers for Disease Control site describing how “to keep your family healthy.”

Although the label “stomach flu” is often used for noroviruses, the viruses are unrelated to the micro-organisms that cause seasonal influenza or other influenza, including the 2009 H1N1 flu (so-called swine flu). One in 15 Americans every year are reportedly affected by norovirus, which causes sudden vomiting, diarrhea, and stomach cramps that continue for 24 to 48 hours.

In response to the outbreak at Rider University, the makers of Lysol say that they are donating 200 cases of disinfectant spray and disinfecting wipes — 2,400 products in total — to the Rider Student Health Services department for widespread campus distribution.