Meningococcal W on the Rise in Georgia

The incidence of Neisseria meningitidis serogroup W is rising in Georgia, according to an August 17 Morbidity and Mortality Weekly Report from the US Centers for Disease Control and Prevention (CDC).

“Although not associated with an outbreak, molecular testing indicated that the Georgia serogroup W isolates are all from the same clonal complex, CC11,” confirm Ashley E. Moore, MS, MPH, from the Georgia Department of Public Health, and colleagues. “This strain is associated with an increased morbidity and mortality which could have severe implications.”

Although the United States has been experiencing declining rates of meningococcal disease in past decades, other countries have been reporting increases in cases of serogroup W disease; this rise has occurred because of rapid expansion of a single meningococcal group W clone belonging to CC11, the authors say.

CC11 is considered a hypervirulent meningococcal strain because of its association with severe illness, unusual manifestations, and high case fatality. Unusual manifestations in these cases have included pneumonia, septic arthritis, and epiglottitis/supraglottitis. Some patients have also presented with predominantly gastrointestinal symptoms.

Serogroup W typically accounts for only about 5% of all annually reported cases of meningococcal disease across the United States and this incidence has remained stable in recent years.

In contrast, however, Dr. Moore and colleagues highlight increasing reports of serogroup W in Georgia. Although it accounted for only 3% of meningococcal disease cases reported in the state between 2006 and 2013, serogroup W accounted for 42% of cases from 2014 through 2016.

Of 178 cases of meningococcal disease reported from 2006 to 2016 in Georgia, 21 were associated with serogroup W.

The investigators performed genetic analyses to compare the serogroup W isolates from Georgia with those from patients in other US states and worldwide.

Analysis suggested that the CC11 serogroup W strains from other states might share a common ancestor with the hypervirulent strain that is circulating worldwide, according to the authors.

Of the 21 Georgia isolates, 18 belonged to CC11; 17 of these were sequence type 11, and the remaining one was a new sequence type.

The investigators also found that, while the 17 Georgia isolates were similar to each other, they differed from those from the other states.

Unlike previous reports of serogroup W meningococcal disease, this study did not find any significant differences in the clinical presentation of patients with serogroup W disease compared with patients with non-serogroup W disease.

However, it did find a slightly higher frequency of intensive care unit (ICU) admissions and case fatality in patients with serogroup W disease. One UK report also showed a similar link between ICU admissions and serogroup W disease, the authors note.

Dr. Moore and colleagues stress that the recent global expansion of this potentially hypervirulent meningococcal strain has important implications for public health practice.

“The collection and testing of meningococcal isolates for serogroup and strain information is important to monitor changes and emergence of previously underrepresented serogroups,” the authors conclude.

Dr. Parry graduated from the University of Liverpool, England in 1997 and is a board-certified veterinary pathologist. After 13 years working in academia, she founded Midwest Veterinary Pathology, LLC where she now works as a private consultant. She is passionate about veterinary education and serves on the Indiana Veterinary Medical Association’s Continuing Education Committee. She regularly writes continuing education articles for veterinary organizations and journals and has also served on the American College of Veterinary Pathologists’ Examination Committee and Education Committee.