Response to a Serogroup B Meningococcal Disease Case Among Military Trainees

Abstract

We describe the public health response to a military trainee who developed serogroup B meningococcal disease while sharing underwater breathing equipment. Despite high transmission risk, with rapid isolation and postexposure prophylaxis administration, there were no secondary cases. This case supports carefully weighing serogroup B meningococcal vaccination in high-risk settings.

Neisseria meningitidis has caused numerous outbreaks among military trainees living in congregate settings. The incidence of meningococcal disease has decreased over the last several decades with the introduction of the quadrivalent vaccine against serogroups A, C, W, and Y [1]. Serogroup B meningococcal vaccination is only recommended for adolescents with specific medical conditions, such as asplenism, or if a patient is in a community that is experiencing a serogroup B meningococcal outbreak, which is defined as 2 cases in a 3-month period within an organization [2]. Recent surveys of nasopharyngeal meningococcal carriage in asymptomatic college students in the United States (US) have shown that while serogroup B was the most commonly isolated typeable strain of N meningitidis, it was present in <3% of the screened population [3]. Despite its low prevalence, serogroup B meningococcus has been associated with numerous outbreaks among people between the ages of 18 and 24 years. Even so, >70% of serogroup B cases are sporadic and not associated with development of an outbreak [4].

Recent well-documented outbreaks of serogroup B meningococcus on college campuses with public health responses have included postexposure prophylaxis of close contacts and mass vaccination campaigns [5]. The benefit of mass vaccination after a single case in a high-risk setting is not well documented. This uncertainty is especially true in settings where there are communal practices that could facilitate widespread transmission. In this manuscript, we describe the public health response to a case of serogroup B meningococcal disease in a group of military trainees participating in water-based training activities where there was use of “buddy breathing,” during which common breathing equipment is shared between multiple military trainees to prepare for diving emergencies. Despite their frequent use of shared breathing equipment, along with their already known risk of living in a congregate military setting, we observed no secondary cases following our public health interventions, which ultimately did not include mass vaccination for serogroup B meningococcus.

CASE REPORT

A 21-year-old military special warfare trainee presented to sick call with headache, neck stiffness, myalgia, vomiting, and purpura on his trunk, extremities, and his soft palate. He was transferred to the emergency department and had a lumbar puncture performed, which revealed a neutrophilic pleocytosis (5348 white blood cells/µL, 85% polymorphonuclear leukocytes), hypoglycorrhachia (<2 mg/dL), elevated protein (312 mg/dL), Gram stain with gram-negative diplococci, and polymerase chain reaction positive for N meningitidis. He was immediately isolated from his training unit and started on intravenous ceftriaxone. The sample from his spinal fluid grew N meningitidis, which whole genome sequencing identified as serogroup B. The patient was successfully treated with a 10-day course of intravenous ceftriaxone and resumed training after completion of his therapy.

Special warfare training is an elite technical school in the US Air Force with unique demands including underwater training. All trainees are vaccinated with a quadrivalent meningococcal vaccine against serogroups A, C, W, and Y. All trainees live in double-occupancy rooms. At the time of this patient’s presentation, his training group of 70 students was in an underwater component of training.

At the time of diagnosis, public health, preventive medicine, trainee health, and infectious diseases responses were coordinated, and exposed trainees were quarantined. As there was significant sharing of breathing equipment between the trainees, all 70 individuals in the training group received prophylaxis with ciprofloxacin within 24 hours of the patient’s presentation, except for the patient’s roommate, who received ceftriaxone within 12 hours of presentation. Diving operations in this group were suspended for 2 weeks after the initial case. The group also underwent daily trainer-directed screening for symptoms of headache, neck pain, fever, or purpura. Five trainees including the patient’s roommate had 1 or more of these symptoms within 7 days after the case, underwent lumbar puncture, and showed no evidence of bacterial meningitis. Four of the 5 contacts had negative blood cultures. As there were no additional cases in the 3-month period following the single-source patient, this event did not meet criteria for an organization-based outbreak [6], and the decision was made not to vaccinate against meningitis B.

DISCUSSION

Meningococcal disease has historically caused significant morbidity and mortality in congregate settings but has considerably decreased with the introduction of the quadrivalent meningococcal vaccine [1].

Serogroup B meningococcal disease has caused several recent outbreaks and is hyperendemic in certain geographic locations around the world [7]. The ideal public health response becomes less clear when the affected population participates in communal activities with significant potential for transmission. The public health response described here documents a successful example where a single case of serogroup B meningococcal disease was contained without need for mass vaccination, even in the setting of shared respiratory equipment.

In the military, meningitis is now a rare diagnosis with the most recent published rate at 0.41 cases per 100 000 person-years: of these, meningococcal disease accounts for one-fifth of the cases [8]. Due to the need for congregate settings as well as shared equipment, meningococcal disease remains a persistent threat to military training environments. Interestingly, with universal vaccination for serogroups ACWY, serogroup B has not become the dominant infecting strain in the military, which also suggests further complexity in the role that vaccination, widespread use of antimicrobials, and prior colonization might play in the occurrence of outbreaks [9].

Many of the recent outbreaks of serogroup B meningococcal disease have occurred in university settings [4]. The military training environment has many similarities with universities, but also key differences. Both groups live in congregate settings, have history of meningococcal outbreaks, and have quadrivalent meningococcal vaccine requirements. In addition, both populations are comprised of late adolescents, the subgroup that has been shown to have more frequent nasal carriage of serogroup B than the general population [10]. However, higher rates of meningococcal colonization have been reported in military recruits as compared to university students [11]. Furthermore, unlike university settings, trainees spend full days together and practice different military techniques with shared equipment, which may be a nidus for disease transmission, despite strategies that have been introduced to mitigate respiratory pathogen spread [12].

There are 2 US Food and Drug Administration–approved vaccines against serogroup B N meningitidis (MenB-4C and MenB-FHbp), which have successfully been implemented in previous outbreaks on college campuses [4]. Since meningococcal group B capsule is an auto-antigen and is minimally antigenic, current group B vaccines use 1 or more protein targets that are more subject to strain variation than the polysaccharide conjugate vaccines used for non-B strains [13]. Along with having a different underlying pathway for immune response, concerns with the effect of vaccination reducing transmission have been raised by reports showing that serogroup B vaccination is not associated with decreased nasal carriage of N meningitidis [14]. Furthermore, the protein targets used in vaccines against serogroup B display antigen variation, which may allow isolates to escape vaccine pressure, even in highly vaccinated populations [15]. With these questions regarding population-level impacts of vaccination, the current recommendations are to reserve vaccination to the highest-risk settings [2].

The use of pharmaceutical interventions such as postexposure prophylaxis, as well as nonpharmaceutical interventions such as isolation of the source patient and suspension of “buddy breathing” for 2 weeks after the case was identified, was sufficient to limit spread in this case without the addition of mass vaccination. Our description of this meningococcal case in a potentially high-transmission-risk environment may serve as a case-based example for the use of pharmaceutical and nonpharmaceutical interventions on limiting spread while carefully weighing the use of group B meningococcal vaccine.

Notes

Acknowledgments. We are grateful to the 37th Training Wing for assistance in the response to this case.

Patient consent. This work received a nonresearch determination approval from the 59th Medical Wing Institutional Review Board. No factors necessitating patient consent applied to the work.

Potential conflicts of interest. All authors: No reported conflicts of interest.

All authors have submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Conflicts that the editors consider relevant to the content of the manuscript have been disclosed.