Haemophilus influenzae is a bacterium commonly found in the nose and throat. Despite its name, it is distinct from the influenza virus and does not cause the flu. This organism can spread from person to person. It often exists harmlessly, but it can cause a range of infections, from mild to severe, depending on the specific strain and the individual’s health.
Understanding Haemophilus influenzae
Haemophilus influenzae is a type of bacteria, not a virus. It is categorized into different strains, primarily by the presence of an outer protective layer called a capsule. Encapsulated strains are classified into six types, ‘a’ through ‘f’, with Haemophilus influenzae type b (Hib) being the most well-known.
Non-encapsulated strains, also known as non-typeable Haemophilus influenzae (NTHi), are genetically diverse and frequently part of the normal human flora. While the Hib strain was historically responsible for most severe infections, non-typeable strains are now more common in causing certain diseases.
How It Spreads
Haemophilus influenzae spreads primarily through respiratory droplets. These droplets are released when an infected person coughs or sneezes. Individuals can become infected by breathing in these airborne droplets or through close contact with someone carrying the bacteria.
Transmission can occur even from individuals who carry the bacteria but show no signs of illness. The bacteria typically enter the body through the upper respiratory tract. While contagious, not everyone exposed will develop an infection. The period of contagiousness can vary, lasting as long as the bacteria are present in the nose or throat.
Conditions Caused by the Bacterium
Haemophilus influenzae can cause a variety of infections. These are broadly categorized into non-invasive and invasive diseases. Non-invasive infections typically affect mucous membranes and include common conditions such as:
Ear infections (otitis media)
Sinus infections (sinusitis)
Bronchitis
These are frequently caused by non-typeable strains.
Invasive diseases occur when the bacteria enter normally sterile parts of the body, like the bloodstream or spinal fluid. These can be life-threatening and include:
Meningitis (infection of the brain and spinal cord lining)
Epiglottitis (a severe throat infection that can block the airway)
Pneumonia (lung infection)
Bacteremia (bloodstream infection)
Cellulitis (skin infection)
Septic arthritis (joint infection)
Before widespread vaccination, Hib was the leading cause of bacterial meningitis in young children and a major cause of other severe invasive diseases.
Protecting Against Infection
Protecting against Haemophilus influenzae infection primarily involves vaccination, particularly against the Hib strain. The Hib vaccine has proven highly effective in preventing severe childhood diseases caused by this specific type of bacteria. The Centers for Disease Control and Prevention (CDC) recommends Hib vaccination for all children younger than 5 years old, with infants typically receiving a series of doses starting around 2 months of age. This widespread immunization has dramatically reduced the incidence of invasive Hib disease.
General hygiene practices also reduce the spread of Haemophilus influenzae. These include:
Frequent handwashing
Covering coughs and sneezes
Avoiding sharing personal items like eating utensils
If an infection occurs, it is typically treated with antibiotics. The specific medication and duration of treatment depend on the infection’s severity and location. In some instances, close contacts of individuals with Hib disease may receive preventive antibiotics to reduce their risk of illness.