Pneumococcal Disease Outbreak at a State Prison, Alabama, USA, September 1–October 10, 2018

A pneumococcal disease outbreak caused by Streptococcus pneumoniae serotype 12F occurred in a state prison in Alabama, USA. Among 1,276 inmates, 40 cases were identified (3 confirmed, 2 probable, 35 suspected). Close living quarters, substance use, and underlying conditions likely contributed to disease risk. Prophylaxis for close contacts included azithromycin and 23-valent pneumococcal polysaccharide vaccine.

A pneumococcal disease outbreak caused by Streptococcus pneumoniae serotype 12F occurred in a state prison in Alabama, USA. Among 1,276 inmates, 40 cases were identifi ed (3 confi rmed, 2 probable, 35 suspected). Close living quarters, substance use, and underlying conditions likely contributed to disease risk. Prophylaxis for close contacts included azithromycin and 23-valent pneumococcal polysaccharide vaccine.
defined as suspected cases with S. pneumoniae isolation or positive urinary antigen test.
We conducted retrospective case finding among inmates who were seen in the clinic during September 1-September 29 and prospective surveillance during September 30-October 10. Cases in which inmates reported respiratory illness, altered mental status, headache, or fever and those without a listed chief complaint were flagged for medical chart review. Inmates whose medical records indicated signs or symptoms of pneumococcal disease were interviewed by using a standardized questionnaire to identify clinical characteristics, risk factors, and epidemiologic links with confirmed cases. For prospective surveillance, we screened all inmates who experienced respiratory symptoms for pneumococcus and influenza by using nasopharyngeal swabs. We tested influenza-negative swab specimens for other respiratory pathogens by using the BioFire FilmArray Respiratory Panel (bio-Mérieux, https://www.biomerieux.com). We performed pneumococcal serotyping on nasopharyngeal swab specimens from which S. pneumoniae was isolated. We calculated attack rates by dividing the number of identified cases by the at-risk population (i.e., all dormitory residents). Specimen culture and antibiotic susceptibility testing was performed at laboratories in the hospitals in which patients received care and confirmed at the Centers for Disease Control and Prevention. Sterile body fluids and nasopharyngeal swab specimens were sent to Centers for Disease Control and Prevention for species detection, confirmation, and serotyping by using real-time reverse transcription PCR. Bacterial serotyping and whole-genome sequencing (WGS) were performed on pneumococcal isolates collected from confirmed cases. We analyzed single-nucleotide polymorphisms identified through WGS to verify temporal relatedness of the isolates.
Blood (n = 5) or cerebrospinal fluid (n = 4) specimens were collected from 5 patients. Three S. pneumoniae isolates were identified from 3 patients (2 from cerebrospinal fluid, 1 from blood); all 3 were serotype 12F. WGS demonstrated a 2-5 single-nucleotide polymorphism difference among isolates, indicating all confirmed cases were closely related. Antimicrobial susceptibility testing confirmed isolate susceptibility.
During prospective surveillance, we collected nasopharyngeal swab specimens from 2 inmates; S. infantis serotype 13 was detected in 1 specimen and adenovirus only in the other. No additional cases were identified. Prophylaxis with PPSV23, which protects against serotype 12F, and 2 doses of azithromycin were offered to inmates and close contacts living in or assigned to dormitory X, clinic staff, and prison employees (Table 2).

Conclusions
This investigation highlights the outbreak potential of S. pneumoniae and demonstrates that correctional facilities remain at risk for pneumococcal outbreaks after PCV introduction in the United States. documented pneumococcal disease outbreak at a US correctional facility also involved serotype 12F and occurred in 1989 in a crowded Texas jail, in which 46 inmates experienced pneumonia, meningitis, or sepsis over a 4-week period (11). Unlike jails, which have an average detention length of <2 months, prisons have lower rates of inmate turnover because they are designed for long-term incarceration; the average detention among US state prisoners in 2016 was 2.6 years (12). However, jails and prisons are similar in that they share risk factors for outbreaks, such as potential overcrowding and increased medical and behavioral risk factors for communicable diseases (13). Decreases in pneumococcal disease have been observed during outbreaks after administering prophylactic antibiotics and PPSV23 to high-risk persons (6,7,11,14). Risk for pneumococcal disease outbreaks in prisons can be minimized by offering inmates vaccinations per Advisory Committee on Immunization Practices recommendations, which recommend PPSV23 for persons with chronic heart, liver, or lung disease (15). Risk can be further reduced by minimizing inmate crowding, eliminating indoor smoking, and ensuring adequate ventilation (11).  One limitation of this study was that risk factor information was collected by self-reporting and might be underestimated. Disease etiology was not confirmed for most cases because few patients had confirmatory laboratory testing for respiratory pathogens. Dormitories were not assessed for space, capacity, or ventilation.
Pneumococcal colonization among inmates could not be widely assessed. We observed decreases in pneumococcal disease after prophylaxis administration, but we cannot determine the direct impact of prophylaxis since S. pneumoniae serotype 12F carriage was not measured. Pneumococcal carriage studies among incarcerated populations could further our understanding of pneumococcal disease in correctional facilities.
In our outbreak investigation of pneumococcal disease in a state prison, we observed decreases in disease after prophylaxis with PPSV23 and azithromycin. Increased pneumococcal disease risk might have resulted from close living quarters, substance use, and underlying conditions. Improved pneumococcal disease surveillance and proactive vaccination of at-risk inmates in accordance with Advisory Committee on Immunization Practices recommendations might mitigate risk for and scale of future outbreaks.