Why an Outbreak at Princeton?

For the past nine months, Princeton University has been trying to halt an outbreak of bacterial meningitis in its students without success. Since bacterial meningitis is a serious infection of the brain and spinal cord that can cause brain damage and death, having it on campus is no small matter.

The situation at Princeton, where eight students have fallen ill, has had students thinking — why is the meningitis outbreak at Princeton? PPHR asked Woodrow Wilson School Professor Adel Mahmoud, a global health policy and disease control expert to discuss his views on the subject.

Like most communicable disease, meningitis affects adolescents and young adults. But meningitis occurs in all age groups and states in the U.S. Most cases are sporadic; they just happen individually, and that’s it. In fact, with no relationship to season, geography, or surroundings, 98% of meningitis cases are sporadic.

Unluckily for Princeton, the sporadic cases this year have all been on campus. Mahmoud explained, “Sometimes, it happens in classes. It’s hard to find an explanation. Since we know humans are the only source of infection, they are the only carriers and only source of transmission; it just happens.”

But outbreaks do occur. And it has to do with sustained patterns for social interactions among college students. “It is the unfortunate happenings that someone got closer to someone that had it,” said Mahmoud.

The disease is transmitted either by close contact or face-to-face prolonged contact. It’s carried through large respiratory droplets or oral secretions. It requires close, fairly intimate contact.

But it might seem arbitrary to label eight significantly sporadic cases of meningitis become as an outbreak. Mahmoud shared his hypothesis as to why the incidences were initially not considered an outbreak, but later received that name: The three cases that occurred last spring were happening in the “right” seasons – winter to early spring. While there is no definite characteristic as to who is a carrier and who is not, the three Princeton cases were assumed to be sporadic and gave no reason for the Centers of Disease Control and Prevention or the New Jersey Department of Health to label what was happening as an outbreak. Now, with an estimated current population of 8,000 students at Princeton, eight cases have arisen in nine months. This appears significantly higher than the expected incidence rates of meningitis B in the U.S., resulting in the labeling of a “Princeton outbreak.”

Generally speaking, meningitis outbreaks involve a type of bacteria called Neisseria meningitidis or meningococcus. But those bacteria are divided into strains or serogroups. The vaccines that are recommended routinely cover four serogroups: A, C, W-135 and Y. Traditionally, outbreaks involve serogroup C, and cases tend to occur in a short period of time very quickly and closely, back-to-back.

The outbreak in Princeton involves serogroup B, which isn’t covered by the vaccine that is approved for use in the United States. With the B strain, there can be weeks or even months between cases. So in this situation, it allows for more time to mobilize and vaccinate the population. But it also means it is harder to know when the outbreak has finished.

By looking at the molecular definition of bacteria in the first six cases so far, Mahmoud confirms that they are all very similar: “the strain, or subtype, that is causing this outbreak is the same bug – a really aggressive bug.” Unfortunately for Princeton, this is not unusual; such outbreaks happen and are hard to prevent or predict.

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