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Invasive Hia infections emerging in Alaskan children
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Since introduction of the Haemophilus influenzae type b conjugate vaccine, Haemophilus influenzae type a infections have become a major invasive bacterial disease of concern in Alaska Native children, according to recent study results published in Emerging Infectious Diseases.
“[Haemophilus influenzae type a] was not identified in Alaska until 2002 and has since increased and caused outbreaks,” researchers wrote. “Although it is possible that [Haemophilus influenzae type a] existed in Alaska before 2002, it is unlikely that it was commonly circulating during the 1980s and 1990s.”
The study included data from 1983 to 2011 and identified 958 cases of invasive H. influenzae disease; 866 of these were available for serotyping.
Researchers found that 617 were serotype b isolates, 158 were non-typeable, 44 were serotype f, 32 were serotype a, 13 were serotype e and two were serotype d. From 2002-2011, 52% of non-serotype b isolates were identified as Haemophilus influenzae type a (Hia), which was not identified until 2002.
They also found that incidence of the invasive Hia from 2002 to 2011 was 5.4 per 100,000 population (95% CI, 3.6-7.7) among children aged younger than 5 years; however, the rate in Alaska Native children (18/100,000) was 36 times higher than among non-Native children (0.5/100,000). More recently, from 2009 to 2011, an outbreak of invasive Hia disease was documented in one Alaska region with rates as high as 204 cases per 100,000 population among children aged younger than 5 years. The most common clinical syndromes for the 32 invasive Hia cases were meningitis (38%), pneumonia (34%) and septic arthritis (19%); 84% of cases were hospitalized and three died.
“In Alaska, invasive Hia disease is severe and similar (in terms of its very serious clinical syndrome) to invasive Hib disease that we saw in the past prior to use of Hib conjugate vaccine,” Michael G. Bruce, MD, MPH, of the CDC, told Infectious Diseases in Children. “Development of a conjugate vaccine for Hia is particularly important for the US Arctic (Alaska) and the Northern Territories of Canada, where rates in some areas are comparable to invasive Hib rates seen in the pre-vaccine era.”
Disclosure: The study was supported by CDC.
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