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Background Incidence of invasive disease due to H. influenzae serotype a (Hia) increased an average of 13% annually from 2002–2015. We described clinical characteristics and adverse clinical outcomes of U.S. invasive Hia cases detected through multi-state surveillance during 2011–2015. Methods Medical record data were abstracted for cases reported in eight jurisdictions conducting active population- and laboratory-based surveillance for invasive Hia disease across the United States. Isolates from sterile sites were serotyped by real-time polymerase chain reaction. Adverse clinical outcomes were defined as any possible complication of meningitis, bacteremic pneumonia, or bacteremia (including hearing loss, developmental delay, and speech delay, but excluding death), and were assessed at hospital discharge and one-year post-disease onset. Results During 2011–2015, 190 Hia cases were reported to the eight participating sites; 169 (88.9%) had data abstracted. Many patients were aged <5 years (42.6%) or ≥65 years (20.7%). Meningitis was the most common clinical presentation among <1 year olds (71.4%); bacteremic pneumonia was the most common presentation among persons aged ≥50 years (78.7%). Overall, 95.9% of patients were hospitalized: among those hospitalized, 47.5% were admitted to an intensive care unit, and 6.2% died during hospitalization. At hospital discharge and one-year post-disease onset, adverse outcomes were identified in 17.7% and 17.8% of patients overall, and in 43.9% and 48.5% of patients with meningitis (primarily children). Conclusions Hia infection can cause severe disease requiring hospitalization and may also cause short- and long-term adverse clinical outcomes, especially among children. Novel vaccines could prevent morbidity and mortality.

BackgroundRates of invasive group A Streptococcus (iGAS) disease in the United States have risen since 2014; reasons remain unclear. Outbreaks of iGAS infection among persons experiencing homelessness (PEH) and persons who inject drugs in Europe, Canada, and the United States have been described. Using active, population-based surveillance data from California’s Emerging Infections Program, we describe incidence trends and characteristics of iGAS infection among PEH and persons not experiencing homelessness (PNEH) in San Francisco (SF) County during 2010–2017.MethodsWe defined an iGAS case as infection with GAS isolated from a normally sterile site (e.g., blood) in an SF resident. We calculated annual iGAS disease incidence rates (cases per 100,000 population) for PEH and PNEH using denominators from SF’s Department of Homelessness and Supportive Housing and the State of California Department of Finance. Demographic, clinical, and exposure characteristics of PEH and PNEH were compared by chi-square or t-test.ResultsWe identified 673 iGAS cases in SF during 2010–2017. Among these, 34% (229/673) were among PEH. Annual iGAS incidence among PEH rose from ~300 (2010–2014) to 547 (95% CI: 379–714) per 100,000 in 2017 (P < 0.001, Cochran-Armitage trend test); rates peaked at 758 (95% CI: 561–955) in 2016. Annual iGAS incidence in PNEH rose from a mean of 5 in 2010–2013 to 9.3 (95% CI: 7.3–11.4) per 100,000 in 2017 (P < 0.001). Annual iGAS incidence in PEH was 42–72 times that in PNEH. PEH with iGAS infections were significantly younger and more likely to be male, white, and uninsured or enrolled in Medicaid (P < 0.05 for each) compared with PNEH with iGAS disease. Case fatality ratios, ICU admission, infection type, and length of hospital stay did not differ significantly. Smoking, current injection drug use, current alcohol abuse, and AIDS diagnosis were significantly more common among PEH with iGAS. Obesity, diabetes, and cancer were significantly more common among PNEH with iGAS.ConclusionIn San Francisco, iGAS rates among both PEH and PNEH have risen significantly. Incidence of iGAS is strikingly higher in PEH than in PNEH and exposures differed between PEH and PNEH with iGAS. This information could inform development of disease control and prevention strategies.Disclosures All authors: No reported disclosures.