Streptococcus pneumoniae outbreaks and implications for transmission and control: a systematic review

Abstract

Background: Streptococcus pneumoniae is capable of causing multiple infectious syndromes and occasionally causes outbreaks. The objective of this review is to update prior outbreak reviews, identify control measures, and comment on transmission.

Methods: We conducted a review of published S. pneumoniae outbreaks, defined as at least two linked cases of S. pneumoniae.

Results: A total of 98 articles (86 respiratory; 8 conjunctivitis; 2 otitis media; 1 surgical site; 1 multiple), detailing 94 unique outbreaks occurring between 1916 to 2017 were identified. Reported serotypes included 1, 2, 3, 4, 5, 7F, 8, 12F, 14, 20, and 23F, and serogroups 6, 9, 15, 19, 22. The median attack rate for pneumococcal outbreaks was 7.0% (Interquartile range: 2.4%, 13%). The median case-fatality ratio was 12.9% (interquartile range: 0%, 29.2%). Age groups most affected by outbreaks were older adults (60.3%) and young adults (34.2%). Outbreaks occurred in crowded settings, such as universities/schools/daycares, military barracks, hospital wards, and long-term care facilities. Of outbreaks that assessed vaccination coverage, low initial vaccination or revaccination coverage was common. Most (73.1%) of reported outbreaks reported non-susceptibility to at least one antibiotic, with non-susceptibility to penicillin (56.0%) and erythromycin (52.6%) being common. Evidence suggests transmission in outbreaks can occur through multiple modes, including carriers, infected individuals, or medical devices. Several cases developed disease shortly after exposure (< 72 h). Respiratory outbreaks used infection prevention (55.6%), prophylactic vaccination (63.5%), and prophylactic antibiotics (50.5%) to prevent future cases. PPSV23 covered all reported outbreak serotypes. PCV13 covered 10 of 16 serotypes. For conjunctival outbreaks, only infection prevention strategies were used.

Conclusions: To prevent the initial occurrence of respiratory outbreaks, vaccination and revaccination is likely the best preventive measure. Once an outbreak occurs, vaccination and infection-prevention strategies should be utilized. Antibiotic prophylaxis may be considered for high-risk exposed individuals, but development of antibiotic resistance during outbreaks has been reported. The short period between initial exposure and development of disease indicates that pneumococcal colonization is not a prerequisite for pneumococcal respiratory infection.

Keywords: Cluster; Epidemic; Outbreaks; Pneumococcal vaccine; Pneumococcus; Streptococcus pneumoniae; Transmission.

Fig. 1

Reported Streptococcus pneumoniae outbreaks by anatomical site. LRTI: Lower respiratory tract infection. LRTI was divided into three eras; pre-vaccine (pre-1977), pneumococcal polysaccharide vaccine only (1977–1999), and pneumococcal polysaccharide and conjugate vaccines (2000–2017)

Fig. 2

Streptococcus pneumoniae outbreaks by setting. LTCF: Long-term care facility. Graphic includes outbreaks from all anatomical sites (94 outbreaks)

Fig. 3

Pneumococcal lower respiratory tract infection outbreak serotypes and coverage by pneumococcal vaccines. Green: both the 13-valent pneumococcal conjugate vaccine (PCV13) and 23-valent pneumococcal polysaccharide vaccine (PPSV23) cover the indicated serotype. Blue: only PPSV23 covers the indicated serotype. Hatched bars indicate serogroups that have subtypes covered by the vaccines, but the specific serotype within the serogroup was not consistently reported across publications. The graph is subdivided by vaccine era; PPSV only (1977–1999) and PPSV/PCV (2000–2017)

Fig. 4

Modes of person-to-person transmission of Streptococcus pneumoniae

Fig. 5

Simplified description of serious Streptococcus pneumoniae infections, with a focus on initial respiratory tract disease. Death, not represented in the figure, can occur at any illness stage with varying survival probability based on disease stage