H. influenzae type b Disease

Dr. Parang Mehta, MD.

Hemophilus influenzae type b is a germ.  A very aggressive bacterium, which affects mainly children under the age of five years.  It causes a range of diseases, many of which are serious and life threatening.

Diseases caused by H. influenzae type b are serious, and drug resistance is increasing. Vaccination has reduced these diseases significantly

Hemophilus influenzae is an important cause of disease in young children.   There are many known types of H. influenzae, but the most serious disease is caused by H. influenzae type b.   About 90% of all serious disease caused by this bug is in children less than 5 years old.

Apart from the fact that all infections are naturally more serious in early childhood, infections caused by Hemophilus influenzae have another problematic aspect.  Most strains of this bacterium produce enzymes called beta lactamases, which destroy antibiotics of the penicillin and cephalosporin group.  Since these are among the most commonly prescribed antibiotics, resistance to them is a major problem.

Diseases Caused

The most important disease caused by H. influenzae type b is meningitis.   This is an infection of the coverings of the brain, and causes fever, vomiting, seizures and unconsciousness.   Death rates are up to 20%, and the survivors often have residual problems.   These include behavioural problems, seizures, deafness, vision defects, mental retardation, and hydrocephalus (collection of water in the brain).

Before the vaccine against this bug was introduced, more than three quarters of the cases of childhood memingitis were caused by Hemophilus influenzae.

Cellulitis is an infection of the tissues under the skin.   It can spread very rapidly, and the child may become seriously ill.

Epiglottitis is an infection of the epiglottis - a small structure inside the throat.   The infection is accompanied by marked swelling, which can obstruct breathing.   It is considered an emergency because of potential for sudden death.

Pneumonia in children under the age of 4 years is often due to H. influenzae type b.   It is difficult to differentiate from pneumonia caused by other germs.  If not treated adequately, this can be serious and even fatal.

Other diseases include septic arthritis (infection of a joint), otitis (infection of an ear), osteomyelitis (infection of a bone), bacteremia (bacteria circulating in the blood), and pericarditis (infection of the coverings of the heart).

Prevention

H. influenzae causes serious and life-threatening disease, and the antibiotic resistance the bug has makes such infections a high risk situation.  Protective measures are therefore very important.

Vaccines against H. influenzae type b have been available for some time now, and are being given to all children in many countries.   Together, this vaccine and the pneumococcal vaccine have reduced the incidence of meningitis in children to a small fraction of the earlier incidence.

The schedule of the vaccine depends on the age at which vaccination is begun.   If the first dose is given in the first six months of life, another two should be given, at intervals of 4-8 weeks between each two doses.   These should be followed by a booster dose at the age of 15 months.

If the first dose is given after six months, only one more dose is recommended, after 4-8 weeks, followed by the booster dose at 15 months.  If the first dose is delayed beyond one year, it should be followed by only the 15 month booster.   If the child is unvaccinated beyond 15 months, only a single dose is adequate.   Infection by H. influenzae is rare after the age of 5 years, and the vaccine is not recommended after this age.

It sounds attractive to vaccinate a child after the age of 15 months, as only a single dose will be needed.  However, it is a dangerous strategy as the disease is common and dangerous in the first year of life.

 

Last Revision: May 22, 2020