Does Haemophilus influenzae bacteria cause the flu?

Despite its name, Haemophilus influenzae bacteria does not cause the flu. The flu is a viral disease caused by the influenza virus, whereas Haemophilus influenzae is a group of bacteria that can cause various types of infections, some mild and others serious [2].

This bacterium is known for its ability to cause a wide range of diseases, particularly its type known as Haemophilus influenzae type b (Hib), which can lead to serious health complications, especially in young children. It is important to understand the difference between bacterial and viral infections to manage each of them correctly.

What diseases are caused by Haemophilus influenzae bacteria?

Haemophilus influenzae bacteria can cause many types of infections that vary in severity. Some of these infections are mild, such as ear infections and bronchitis in adults. However, it can cause serious types of infections, especially type b (Hib), which may lead to long-term health problems or death [2].

The most serious diseases caused by the Hib type of Haemophilus influenzae include [1]:

• Pneumonia: A serious infection of the lungs.
• Bacteremia (bloodstream infection): The spread of bacteria into the blood.
• Meningitis: Swelling of the membranes surrounding the brain and spinal cord.
• Epiglottitis: Swelling in the throat that can cause difficulty breathing.
• Cellulitis: A skin infection.
• Septic arthritis: Swelling in a joint.

How does a Haemophilus influenzae infection spread?

Haemophilus influenzae bacteria typically live in people's noses and throats without causing any harm. However, it can spread to other parts of the body and cause infection. The bacteria spread from person to person through coughing or sneezing, which releases small respiratory droplets containing the bacteria. Other people can become infected if they inhale these droplets [2].

Even people who do not show symptoms of the disease but carry the bacteria in their noses and throats can pass it on to others. The bacteria can also spread to people who have close or prolonged contact with someone infected with a Haemophilus influenzae disease [2].

Preventing Haemophilus influenzae infection with vaccination

The best way to prevent the serious diseases caused by the Hib type of Haemophilus influenzae is through vaccination. The Centers for Disease Control and Prevention (CDC) recommends the Hib vaccine for all children under 5 years of age [3]. The vaccine is usually given in several doses at the following ages [3]:

• 2 months
• 4 months
• 6 months (if necessary, depending on the vaccine type)
• 12 to 15 months

Older children and adults generally do not need the Hib vaccine, unless they have certain medical conditions or have received a bone marrow transplant [3]. Vaccines are very effective at protecting against Hib disease, but they cannot prevent all cases [3]. You can learn more about this topic by visiting Preventing Haemophilus influenzae infection with vaccination (Arabic).

Side effects of the Hib vaccine and when to seek emergency care

Most people who receive the Hib vaccine do not experience any problems. Mild side effects are uncommon, and if they occur, they usually begin shortly after receiving the vaccine and last for up to two or three days [3]. These side effects may include:

• Redness, warmth, or swelling at the injection site.
• Fever.

Although serious reactions are rare, they are possible [3]. If your child shows any signs of a severe allergic reaction after vaccination, such as difficulty breathing, swelling of the face and throat, or severe dizziness, you should seek emergency medical care immediately. Generally, the vaccine can be received while suffering from mild illnesses such as a cold, but you should consult a healthcare provider if there is any concern [3].

Medical references

• About Haemophilus influenzae Disease
• Haemophilus Infections
• Hib Vaccination