Saturday, March 31, 2012


Holly has been feeling our baby move for a couple of weeks. This morning, she put my hand on her belly and I felt it moving for the first time.

We're experiencing and unusually high number of cases of pertussis in Washington State. This week I sent an Email to my parents and siblings asking them to get a Tdap if they haven't already had one.

I'm finishing up my discussion of tetanus, diphtheria, and acellular pertussis vaccine (Tdap) with this post on the D in Tdap and DTaP: diphtheria.

1874: Maria and Sven Larson
lost five children to diphtheria
Jone Johnson Lewis
Before the introduction of diphtheria toxoid vaccines in the mid-1940s, major diphtheria epidemics occurred roughly every 25 years. One epidemic in New England killed about a third of all children. Between 1921 and 1924, diphtheria was the leading cause of death of Canadian children 2 to 14 years of age. When immunization levels dropped, a diphtheria epidemic occurred in the former Soviet Union between 1990 and 1996. The last outbreak of diphtheria in the United States occurred in alcoholics in Seattle from 1972 to 1982.

The name diphtheria comes from the Greek word for "leather." The reason is that a tough, leather-like pseudomembrane forms over the tonsils, uvula, throat (pharynx), voice box (larynx), and sometimes into the wind pipe (trachea) of persons with respiratory diphtheria. The pseudomembrane contains dead epithelial cells, red and white blood cells, fibrin, and bacteria.

Like tetanus vaccine, diphtheria vaccine is a toxoid which stimulates the immune system to make antibodies to a toxin produced by the bacteria. Corynebacterium diphtheriae only produces diphtheria toxin when it is infected with a bacteriophage; a virus that infects bacteria. The phage carries the gene that codes for diphtheria toxin. C. diphtheriae that lack this gene are called nontoxigenic.

Although diphtheria toxin can affect any tissue in the body, its worst effects are on the heart, peripheral nerves, and kidneys. Diphtheria toxin also causes the neck to swell (edema) causing a "bullneck" appearance. Death from diphtheria can occur from suffocation either by the swelling in the neck or by a portion of dislodged pseudomembrane occluding the airway. Death can also result from a cardiac arrhythmia caused by diphtheria toxin. Because of its neurotoxicity, diphtheria toxin causes muscle weakness and paralysis, including the muscles involved in swallowing and protect the airway.

Diphtheria is usually transmitted by respiratory droplets. C. diphtheriae is not known to infect animals. Diphtheria can infect the skin, causing sores that are covered by a membrane and do not heal. Cutaneous diphtheria usually does not cause severe disease but may be a reservoir for respiratory diphtheria infections.

Diphtheria infection does not reliably result in immunity to the disease. The level of protective antibodies from immunization or infection decreases over time, which is why diphtheria toxoid is given to adults in combination with tetanus toxoid every ten years – "tetanus boosters" are actually tetanus and diphtheria boosters.

According to the Centers for Disease Control and Prevention (2010), 64% of adults 19 to 49 years of age have received a tetanus and diphtheria vaccine in the last ten years. Immunization rates decrease with age and are highest among whites, lowest among Asians. Despite the ACIP recommendation, only 8.2% of adults 19 to 64 years of age reported receiving a Tdap.

Even though there have been no cases reported in the U.S. since 2003, there is a risk of importation from countries where diphtheria remains endemic. Tetanus spores are present in the environment, and the incidence of pertussis has been increasing in recent years. These three diseases are still a risk to people living in the U.S., but they are controllable with immunization.

Additional information:

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Centers for Disease Control and Prevention. (2010). Adult vaccination coverage – United States, 2010. Morbidity and Mortality Weekly Report, 61(4), 66-72.

Centers for Disease Control and Prevention. (2011). Diphtheria.

Golaz, A., Hardy, I. R., Strebel, P., Bisgard, K. M., Vitek, C., Popovic, T., & Wharton, M. (2000). Epidemic diphtheria in the Newly Independent States of the former Soviet Union: implications for diphtheria control in the United States. Journal of Infectious Diseases, 181(Supple. 1), S237-S243.

Harnisch, J. P., Tronca, E., Nolan, C. M., Turck, M., & Holmes, K. K. (1989). Diphtheria among alcoholic urban adults. A decade of experience in Seattle. Annals of Internal Medicine, 111(1), 71-82.

MacGregor, R. R. (2009). Corynebacterium diphtheriae. In G. L. Mandell, J. E. Bennett, & R. Dolin (Eds.), Mandell, Douglas, and Bennett's principles and practice of infectious diseases (7th ed.). [Electronic version].

Overturf, G. D. (2009). Corynebacterium diphtheriae. In S. S. Long (Ed.) Principles and practice of pediatric infectious diseases (3rd Ed.). [Electronic version].

Vitek, C. R. & Wharton, M. (1998). Diphtheria in the former Soviet Union: reemergence of a pandemic disease. Emerging Infectious Diseases, 4(4), 539-550.

Vitek, C. R. & Wharton, M. (2008). Diphtheria toxoid. In S. A. Plotkin, W. A. Orenstein, & P. A. Offit (Eds.) Vaccines (5th Ed.). [Electronic version].

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