H. influenzae increasing, especially among American Indian and Alaska Native children
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Invasive Haemophilus influenzae serotype a is increasing in the United States overall, with the greatest burden occurring in American Indian and Alaska Native children, according to findings published in Clinical Infectious Diseases.
“This study was initiated in response to a finding in our 2018 article describing current epidemiology and trends in invasive Haemophilus influenzae disease in the United States, which showed that H. influenzae serotype a (Hia) is of particular concern because incidence increased by an average of 13% annually from 2002 to 2015,” CDC epidemiologist Heidi M. Soeters, PhD MPH, told Healio. “We also knew that elevated Hia incidence had been reported among children and indigenous populations in the U.S. and Canada.”
Soeters and colleagues aimed to “dig deeper into this topic by describing the current epidemiology of invasive Hia disease in the U.S. overall and in Alaska specifically, as the epidemiology of Hia in Alaska is distinct from that in the rest of the U.S., and multiple invasive Hia disease outbreaks have occurred there.”
The researchers performed active population-based and laboratory-based surveillance for invasive Hia disease through the Active Bacterial Core surveillance sites, which are supported by the CDC as part of the Emerging Infections Program Network, and from statewide invasive bacterial disease surveillance in Alaska. The researchers serotyped sterile-site isolates via slide agglutination or real-time PCR and determined incidences in cases per 100,000.
From 2008 to 2017, an estimated average of 306 invasive Hia disease cases occurred annually in the U.S., with the incidence increasing by an average of 11.1% each year. Overall, 42.7% of cases occurred in children aged less than 5 years (incidence, 0.64), with the greatest incidence among children aged less than 1 year (incidence, 1.60). The researchers also found that 7.8% of all patients with Hia died; 15.1% of adults aged 65 years and older died, representing the highest case fatality rate.
According to Soeters, American Indian and Alaska Native children aged younger than 5 years experienced the highest Hia disease burden. These children experienced 8 times more disease than children of all other races combined.
In Alaska, people of all ages experienced an Hia disease incidence nearly six times higher than in the rest of the U.S. overall, and children aged younger than 1 year experienced a disease incidence nearly 14 times higher than children in the U.S. overall. The case fatality rate in Alaska was 10.2%, with the vast majority of cases (93.9%) occurring among American Indians and Alaska Natives.
“In the context of increasing Hia incidence and clinical severity similar to H. influenzae serotype b, new prevention strategies, including development of an Hia vaccine, could prevent morbidity and mortality among these vulnerable populations,” Soeters said. “Additional questions remain regarding the frequency with which secondary Hia transmission occurs, the potential need for updated chemoprophylaxis recommendations, and appropriate target populations for a potential Hia vaccine.”
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