Virginia's Serogroup Y Meningococcal Outbreak, 2022–2024

Invasive meningococcal disease (IMD), caused by the bacterium Neisseria meningitidis, is a severe illness that shows up mainly as meningitis or meningococcemia, a bloodstream infection. Outbreaks are uncommon in the United States. When one happens, CDC recommends vaccinating a defined group at higher risk — college students, for example, or people experiencing homelessness. This outbreak in Virginia had no such group.

How it was found

On August 12, 2022, the Virginia Department of Health (VDH) learned of two people hospitalized with IMD in its Eastern Health Planning Region, both with serogroup Y (NmY). Two more NmY cases had been reported there in June and July. Over the previous 10 years the Eastern Region had averaged only one IMD case a year, and Virginia eight a year statewide. The four patients shared no exposures, links or risk factors.

On September 2, 2022, CDC's whole genome sequencing showed that the available isolates, including one from a fifth case, were all sequence type 1466 (ST1466) in clonal complex 174. VDH declared a community outbreak in the Eastern Region that day, set outbreak case definitions and began active case finding through syndromic surveillance and medical records. When seven cases turned up from November 2022 to July 2023 in the Southwest (five) and Central (two) regions among people who had not traveled to the Eastern Region, the regional criterion was dropped, and a statewide outbreak was declared on August 30, 2023.

Outbreak cases by date of symptom onset, Virginia, 2022–2024. CDC.

Who got sick

From June 12, 2022, to March 1, 2024, there were 36 confirmed cases and one probable case. The probable case was an unvaccinated health care provider who fell ill 5 days after caring for a patient; the provider had received preventive antibiotics before testing, and tests were negative.

Most patients lived in urban areas. Four of those without serogroup Y vaccination knew they had HIV, for which vaccination is routinely recommended; the one vaccinated patient had received a polysaccharide vaccine 16 years earlier. Fourteen patients were current or former substance users, and five worked in construction, though not for a common employer or at a common site. Beyond shared demographics, no common affiliation, exposure or risk factor emerged. Patients' home census tracts had an average social vulnerability index of 0.63, and 0.73 for those who died, against 0.4 for Virginia as a whole.

Isolates from 34 cases were sequenced; all were NmY ST1466 with a shared fine-typing profile and no genetic markers of ciprofloxacin or penicillin resistance. Before this outbreak, ST1466 disease was uncommon in the United States.

The response

• Clinicians were told in September 2022 to watch for IMD and keep eligible patients up to date with quadrivalent MenACWY vaccine; HIV providers were reminded that it is recommended for people with HIV aged 2 and older.
• The public got a press release and an outbreak website in March 2023, and statewide messages after August 2023 urging up-to-date vaccination and prompt care for symptoms.
• Close contacts — household members, roommates and anyone exposed to a patient's oral secretions within 10 days of symptom onset — were urged to take preventive antibiotics.
• Selective vaccination. With no definable group to vaccinate, VDH in December 2022 recommended one MenACWY dose, on top of antibiotics, for close contacts who had IMD risk factors and were not up to date, or who were aged 30–60 and unvaccinated in the past 5 years. In August 2023 this went statewide and was widened to all close contacts aged 11 and older, because cases had appeared outside that age range. No further cases occurred among identified contacts, but local staff reported that few people accepted the vaccine, so its effect could not be judged.

What was unusual

• Most patients (86%), including six who died, did not have typical meningitis symptoms.
• The fatality rate, 19.4%, exceeded the national NmY range of 6.5%–17.2% for 2017–2022, though rates up to 27% were reported in 2015–2016. It may reflect chance, a more virulent strain, or delays in diagnosis because symptoms were atypical — and living in more socially vulnerable areas may have made care harder to reach.
• NmY usually strikes adults 65 and older, but the median age here was 47.
• The outbreak fell heavily on Black Virginians: in the Southwest Region, 83% of patients were Black against 12% of residents, possibly reflecting spread within a shared social network. Cases among people with HIV fit a national rise in IMD in that group; ACIP has recommended MenACWY for people with HIV since 2016, yet vaccination rates among the newly diagnosed have been low.

The report's lesson: genome sequencing can decide whether an outbreak exists when cases have nothing obvious in common, uncommon strains can spread among people not thought to be at high risk, and without a clear group to vaccinate, new approaches such as vaccinating close contacts may be worth trying.

Sources

Based on Robinson M, Crain J, Kendall B, et al., "Statewide Outbreak of Neisseria meningitidis Serogroup Y, Sequence Type 1466 — Virginia, 2022–2024," MMWR Vol. 73, No. 43, CDC; a work of the United States government in the public domain. The report places most patients (63.9%) aged "30–60 years" in its text and "30–59" in its table; neither bound is given here for them. It also calls "approximately three quarters" of patients under 65, while its table counts 7 of 36 aged 65 or older; the table's count is used.