Haemophilus influenzae disease


Haemophilus influenzae (H. flu) disease is a name for any disease caused by a bacteria called H. influenzae. Despite the name, H. flu does not cause influenza (the flu).

H. flu bacteria live in the nose and throat and usually cause no harm. However, sometimes the bacteria can move to other parts of the body and cause disease. H. flu spreads from person-to-person via respiratory droplets from coughing or sneezing. People who are not sick but have the bacteria in their noses or throats can still spread the bacteria. This is how H. flu spreads most of the time. H. flu occurs mostly in children under age 5, or in older adults over age 65. Those with certain medical conditions are at increased risk for H. flu disease.


H. flu can cause many different kinds of diseases, from mild ear infections to serious bloodstream infections. Symptoms depend on the part of the body that is infected. Serious disease occurs when H. flu bacteria get into areas of the brain that are normally free from germs. This includes the spine, brain, and bloodstream.


    Common symptoms of pneumonia usually include:

  • Fever


  • Cough


  • Difficulty Breathing

    Difficulty Breathing

  • Muscle Aches

    Muscle Aches

    Bloodstream Infection

    Common symptoms of bloodstream infection usually include:

  • Fever


  • Excessive Tiredness

    Excessive Tiredness

  • Stomach Pain

    Stomach Pain

  • Difficulty Breathing

    Difficulty Breathing


    Symptoms of meningitis typically include sudden onset of:

  • Fever


  • Headache


  • Nausea


  • Confusion


Diagnosis and Treatment

H. flu is usually diagnosed with laboratory tests. Antibiotics are typically used to treat the infection. Depending on how serious the infection is, hospitalization may be required. Other treatments for H. flu can include:

  • Breathing support
  • Medication to treat low blood pressure
  • Wound care for parts of the body with damaged skin


Staying up to date with recommended vaccines and maintaining healthy habits, like washing hands often and not having close contact with people who are sick, helps prevent disease caused by H. flu.

Vaccines can help prevent on type of H. flu disease - H. flu type b disease. There is no vaccine for any other types of H. flu bacteria.

Information for Health Care Professionals

  • H. Flu for Clinicians
  • US CDC: H. flu Surveillance
  • Laboratory Information
  • Antibiotic Prescribing and Use
  • Maine Surveillance Reports for Haemophilus Influenza 2010 | 2011 | 2012 | 2013 | 2014 | 2017 | 2018 | 2019 | 2020 | 2021 (PDF)