Haemophilus influenzae type b

Immunofluorescent image of Haemophilus influenzae type b

Hib kills!

When a friend of mine was a small child, she woke up in the mid­dle of the night, unable to breathe. She man­aged to wake up her par­ents, who called the ambu­lance. Anoth­er friend of mine, who was work­ing on the ambu­lance that night, saved her life by doing an emer­gen­cy tra­cheosto­my. In oth­er words, he cut a hole in her throat for her to breathe through. It was a hor­ri­fy­ing expe­ri­ence for every­one involved. The like­ly cause of the prob­lem was an infec­tion called Haemophilus influen­za type B, or Hib. Hib infec­tions are the main cause of epiglot­ti­tis, which is swelling of the flap that clos­es off the wind­pipe when you swal­low. Thanks to the vac­cine again­st Hib, the inci­dence of Hib infec­tions in the Unit­ed States has gone down by more than 99%. As a result, today’s young doc­tors will nev­er see a case of epiglot­ti­tis in their career.

Haemophilus influenzae type b

Haemophilus influen­zae, or Pfeiffer’s bacil­lus, is a bac­teri­um that lives in the upper res­pi­ra­to­ry tract of human beings. It was once thought to be the cause of influen­za (the flu). But now we know that influen­za is the result of a viral infec­tion.

Many of the strains of H. influen­za have a cap­sule that helps the bac­te­ria hide from the body’s immune sys­tem. The­se strains are sort­ed into 6 dif­fer­ent types (types a through f), accord­ing to the poly­sac­cha­rides found in their cap­sules. Many of the strains of H. influen­zae can cause upper res­pi­ra­to­ry infec­tions, such as sinus infec­tions. How­ev­er, the type b strains (which are called Hib) can cause a seri­ous infec­tion that runs through­out the body. Some­times, it can even get into the flu­id sur­round­ing the brain. This prob­lem is called menin­gi­tis because it caus­es inflam­ma­tion of the meninges, which are the mem­branes that cov­er the brain. This form of menin­gi­tis is a med­ical emer­gen­cy that can kill with­in hours. Here is the sto­ry of one fam­i­ly whose unvac­ci­nat­ed son caught Hib. He is lucky to have sur­vived:

This fam­i­ly was not so lucky.

Thanks to the Hib vac­cine, Hib infec­tion is now rare, as this report from Canada explains: