Haemophilus Influenzae (Invasive)

478 cases in 2024 — near the 5-year baseline of ~764.

What is it?

Invasive Haemophilus influenzae (Hi) disease is caused by H. influenzae bacteria entering the bloodstream, lungs, or meninges. NYS had 478 cases in 2024. The Hib vaccine, introduced in the 1990s, nearly eliminated the most dangerous form (serotype b) in children — one of the great vaccine success stories. Most current invasive disease is caused by non-b serotypes and affects adults with underlying conditions.

How it spreads

Spreads through respiratory droplets from infected people or carriers. H. influenzae commonly colonizes the nose and throat without causing illness; invasive disease occurs when bacteria breach normal barriers.

Symptoms

Meningitis (stiff neck, severe headache, fever), bacteremia (bloodstream infection), epiglottitis (severe throat swelling that can obstruct breathing), pneumonia, and septic arthritis. Symptoms can develop rapidly.

Who is at risk?

Unvaccinated children under 5 (though now rare due to Hib vaccination), adults 65+, immunocompromised individuals, people without a spleen, and those with chronic health conditions.

What you can do

Vaccine information

Hib vaccine is one of the most effective vaccines ever developed — it reduced Hib meningitis in children by over 99%. Part of the standard childhood immunization schedule.

Based on NYSDOH annual communicable disease report. Threat level reflects 2024 case counts compared to the 5-year baseline.