Outbreak of invasive Haemophilus influenzae serotype a disease.

Haemophilus influenzae serotype a is a rare cause of invasive disease. We report 5 cases of invasive H. influenzae type a that occurred in 3 infants living in a remote region of Alaska during the last 6 months of 2003. H. influenzae type a isolates from this outbreak were closely related as determined by pulsed field gel electrophoresis. Continued surveillance is necessary to monitor trends in H. influenzae invasive disease.