The outbreak, which began in January 2002, was caused largely by Streptococcus pneumoniae, a bacteria that usually causes pneumonia and infections of the ear, sinus and blood, a new study says.
In this case, however, an unusual strain of S. pneumoniae caused conjunctivitis, the eye infection popularly known as pink eye, according to the study published in the March 20 issue of the The New England Journal of Medicine.
One of the study's authors, Dr. John H. Turco, director of the Dartmouth College Health Service in Hanover, N.H., says it quickly became apparent that a lot more students than normal were being infected with conjunctivitis.
"Fortunately, this wasn't an outbreak with a serious illness. We were seeing 30 to 40 students a day with this," he says.
Turco says that, at first, college health officials assumed the outbreak was viral because viruses commonly cause pink eye.
Dr. Robert Cykiert, a New York University Medical Center ophthalmologist, explains that viral infections are so common, he probably only sees one bacterial case of conjunctivitis for every six or seven viral cases he sees.
Since so many students were infected, the doctors at Dartmouth tested for bacteria. Much to their surprise, many cultures came back positive for S. pneumoniae. Even when conjunctivitis is caused by bacteria, S. pneumoniae is rarely to blame.
Because it's so unusual for S. pneumoniae to cause conjunctivitis, Turco and his colleagues alerted the U.S. Centers for Disease Control and Prevention (CDC). After studying samples from Dartmouth, the CDC discovered the Dartmouth outbreak was caused by the same strain of bacteria that caused a conjunctivitis outbreak in New York and California in 1980.
The researchers also found this strain of S. pneumoniae differs from those that cause pneumonia and other illnesses because it is not encapsulated. Most strains are contained in a capsule, a shell-like barrier, but this strain was not, which Turco says may be why it caused conjunctivitis instead of more serious illnesses. Without the capsule, Turco says, the bacterium was not as invasive and needed to find a vulnerable area of the body to penetrate.
The outbreak lasted until April when almost all the students left campus for spring break. Turco says the coming of spring break was fortunate because health officials knew it would probably put an end to the outbreak. But at the same time, health officials were concerned that the students would spread the bacterium to other parts of the country. And, that's precisely what happened.
Later in the year, doctors at Princeton University in New Jersey reported an upswing in conjunctivitis cases, and found they were caused by S. pneumoniae. Last fall, there was an outbreak in younger children in Maine, and Turco says he recently got a call from a college in New York where students have been infected with S. pneumoniae conjunctivitis.
"When you have a lot of people in small quarters, often sharing hygiene facilities, they are prone to sharing infections," Cykiert says.
The best way to prevent conjunctivitis is to wash your hands frequently and thoroughly. Dartmouth health officials also dispensed an alcohol-based antibacterial hand gel, though Turco says he doesn't know if it contributed to the end of the outbreak.
Symptoms of conjunctivitis are a gritty feeling in the eye, redness, swelling and either a watery discharge or a white, yellow or greenish discharge. Anyone with these symptoms should see their doctor, he says. Anyone who wears contact lenses should immediately stop wearing them because they can provide a breeding ground for bacteria, Cykiert says.
In college dorms, he adds, it's important that students realize they shouldn't share personal hygiene items such as contact lens paraphernalia or cosmetics.