Hemophilus influenzae

• Haemophilus influenzae disease is a name for any illness caused by bacteria called H. influenzae. Some of these illnesses, like ear infections, are mild while others, like bloodstream infections, are very serious. In spite of the name, H. influenzae do not cause influenza (the flu). Vaccines can prevent one type of H. influenzae (type b or Hib) disease.

Types

• Haemophilus influenzae, a type of bacteria, can cause many different kinds of infections.
• These infections range from mild, ear infections, to serious, like bloodstream infections.

• Doctors consider some of these infections “invasive.” Invasive disease happens when the bacteria invade parts of the body that are normally free from germs.

The most common types of invasive disease caused by H. influenzae are:

• Pneumonia* (lung infection)
• Bloodstream infection
• Meningitis
• Epiglotittis (swelling in the throat)
• Cellulitis (skin infection)
• Infectious arthritis (inflammation of the joint)

H. influenzae can also be a common cause of ear infections in children and bronchitis in adults

Causes

• Haemophilus influenzae disease is a name for any infection caused by bacteria called H. influenzae. There are 6 identifiable types of H. influenzae (named a through f) and other non-identifiable types (called nontypeable). The one that people are most familiar with is H. influenzae type b or Hib.

• These bacteria live in people’s nose and throat, and usually cause no harm. However, the bacteria can sometimes move to other parts of the body and cause infection.

• Experts do not know how long it takes after H. influenzae enter a person’s body for someone to get sick. However, it could take as little as a few days before symptoms appear.

Transmission

• People spread H. influenzae, including Hib, to others through respiratory droplets. This happens when someone who has the bacteria in their nose or throat coughs or sneezes. People who are not sick but have the bacteria in their noses and throats can still spread the bacteria. That is how H. influenzae spreads most of the time.

• The bacteria can also spread to people who have close or lengthy contact with a person with H. influenzae disease.

People at Increased Risk

H. influenzae, including Hib, disease occurs mostly in babies and children younger than 5 years old. Adults 65 years or older, American Indians, Alaska Natives, and people with certain medical conditions are also at increased risk. Those medical conditions include:

• Sickle cell disease
• Asplenia (no spleen)
• HIV infection
• Antibody and complement deficiency syndromes (rare conditions that affect the body’s ability to fight infections)
• Cancer requiring treatment with chemotherapy, radiation therapy, or bone marrow stem cell transplant

Signs and Symptoms

• Haemophilus influenzae can cause many different kinds of infections. Symptoms depend on the part of the body that is infected.

Symptoms of pneumonia usually include:

• Fever and chills
• Cough
• Shortness of breath or difficulty breathing
• Sweating
• Chest pain
• Headache
• Muscle pain or aches
• Excessive tiredness
• Bloodstream Infection

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Sputum Gram stain at 1000x magnification. The sputum is from a person with Haemophilus influenzae pneumonia, and the Gram negative coccobacilli are visible with a background of neutrophils.

Symptoms of bloodstream infection usually include:

• Fever and chills
• Excessive tiredness
• Pain in the belly
• Nausea with or without vomiting
• Diarrhea
• Anxiety
• Shortness of breath or difficulty breathing
• Altered mental status (confusion)
• Bloodstream infection from H. influenzae can occur with or without pneumonia.

Haemophilus influenzae satelliting colonies (pin point) near Staphylococcus aureus (yellow) on blood agar plate.

Symptoms of meningitis typically include sudden onset of:

• Fever
• Headache
• Stiff neck
• Nausea with or without vomiting
• Photophobia (eyes being more sensitive to light)
• Altered mental status (confusion)
• Babies with meningitis may be irritable, vomit, feed poorly, or appear to be slow or inactive. In young babies, doctors may also test the child’s reflexes, which can be abnormal with meningitis.

Haemophilus influenzae requires X and V factors for growth. In this culture, Haemophilus has only grown around the paper disc that has been impregnated with X and V factors. No bacterial growth is seen around the discs that only contain either X or V factor.

Diagnosis

Doctors usually diagnose Haemophilus influenzae infection with one or more laboratory tests. The most common testing methods use a sample of blood or spinal fluid.

Treatment

• People diagnosed with H. influenzae disease take antibiotics, usually for 10 days, to treat the infection. Depending on how serious the infection is, people with H. influenzae disease may need care in a hospital. Other treatments may include:

• Breathing support
• Medication to treat low blood pressure
• Wound care for parts of the body with damaged skin
• When H. influenzae cause milder infections, like bronchitis or ear infections, doctors may give antibiotics to prevent complications. Learn more about using antibiotics for these infections.

Complications

• Even with appropriate treatment, some H. influenzae infections can result in long-term problems or death. For example, bloodstream infections can result in loss of limbs. Meningitis can cause brain damage or hearing loss.

• Complications are rare and typically not severe for bronchitis and ear infections caused by H. influenzae.

Vaccine

• Vaccines can prevent Haemophilus influenzae type b (Hib) disease. However, the Hib vaccine does not prevent disease caused by the other types of H. influenzae. Learn more about Hib vaccination, including who should get vaccinated.

Re-Infection

• This photograph showed an infant being held by his mother while receiving an intramuscular vaccination in his left thigh muscle. A qualified nurse was administering the vaccination while stabilizing the injection site.
• People can get H. influenzae more than once. A previous Hib infection might not protect you from future infection. Therefore, CDC recommends Hib vaccination even if someone has had Hib disease in the past.

Preventive Antibiotics

• H. influenzae can spread to people who have close or lengthy contact with a person with H. influenzae disease. In certain cases, close contacts of someone with H. influenzae disease should receive antibiotics to prevent them from getting sick. A doctor or local health department will make recommendations for who should receive preventive antibiotics.

Hemophilus influenzae Resources
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