An outbreak of invasive meningococcal disease among men who have sex with men has raged on a small but impactful scale in New York City since 2010, but has shown no sign of spreading elsewhere, according to the epidemiologic assessment of the Centers for Disease Control and Prevention.

"There are no other [U.S.] outbreaks we know of," said Dr. Thomas A. Clark, a medical epidemiologist in the Meningitis and Vaccine-Preventable Diseases branch of the CDC "There are sporadic cases [in other U.S. locations], but outbreaks—clusters of cases--are rare. There has not been an experience in the past where an outbreak like this has spread elsewhere," Dr. Clark said in an interview.

"There have been similar clusters of meningococcal disease before, such as an outbreak in men who have sex with men (MSM) in Toronto. Because each meningococcal case is rare and has public health implications, there is a lot of communication about the cases among health departments" at the city and state level and the CDC, he said.

Awareness of the New York outbreak first surfaced last September, with a report from the city’s Department of Health and Mental Hygiene of 12 cases of invasive meningococcal disease (IMD) in New York starting in 2010 among MSM who were also infected with human immunodeficiency virus (HIV). Based on those cases, the Department recommended on Oct. 4, 2012, the meningococcal vaccine for all HIV-infected men who "had intimate contact with another man that he met through a website, digital application (‘App’), or at a bar or party since Sept. 1, 2012."

By early March, New York’s Department of Health focused its earlier vaccination recommendation and filled in some more data on the scope of the outbreak. In a March 6 alert issued to health care providers, the Department cited a total of 22 confirmed, recent cases in New York, all in MSM: 1 in 2010, 4 in 2011, 13 last year, and 4 during the first 2 months of 2013. Seventeen of the 22 cases had resided in Brooklyn or Manhattan. Cases ranged in age from 21 to 59 years; 50% had been black, 27% white, and 18% Hispanic. In addition, 7 of the 22 cases had died, including 3 of the 5 most-recent cases.

In the March alert, the DOH also revised its prior vaccination guidance, now targeting all HIV-infected MSM, and all MSM regardless of HIV status if they "regularly have close or intimate contact with men met through an online website, digital application (‘app’), or a bar or party." The Department noted that during October 2012-early March 2013, approximately 45% of the initial target population – HIV-infected MSM who also met the high-risk criteria – had received a first vaccine dose.

The relatively high, 32% mortality rate of the infections has the Department especially concerned. "We are worried about this outbreak because it can make people ill very quickly," said a Department spokesperson in an interview. "People can be protected by vaccination, but many who are at risk in this outbreak do not yet know they are at risk or do not believe that the risk is great enough to get vaccinated," the spokesperson added. The March 6 alert to providers urged them to recommend the vaccine to their targeted patients; the Department is administering meningococcal vaccine free at its clinics.

Although the 22 cases since 2010 may seem modest, it is enough to meet standards for a meningococcal outbreak, especially when the at-risk population is as tightly defined as New York has made it, commented Dr. Clark. He also agreed that vaccination was the best and only intervention.

"There are no modifiable risk factors" for meningococcal disease. "That’s why vaccination is best," he said. The only other prophylaxis is a short course of antibiotic for people identified as having been in close, household contact with a diagnosed case. The first-line antibiotic prophylaxis regimen is a single dose of ciprofloxacin, although a couple of other antibiotic alternatives are also possible.

The New York outbreak involves the serogroup C strain of Neisseria meningitidis (MMWR 2013;61:1048), which explains at least part of the reason why the outbreak has had a high mortality rate and prompted the Department of Health to refer to it as IMD. N. meningitidis serotype C has been linked to invasive infections by past reports (Epidemiol. Infect. 2006;134:1195-202). "It’s well documented that most if not all outbreaks of serogroup C have higher case-fatality rates," said Dr. Clark.

Coverage of the outbreak in the New York Times in March quoted Dr. Jay Varma, New York’s deputy commissioner for disease control, as saying IMD has been "sort of marching through the community in a way that makes us very scared."

Dr. Clark had no disclosures.

New York's meningococcal disease outbreak remains contained