Diphtheria is disease that affects primarily the upper respiratory system and is caused by the bacterium Corynebacterium diphtheriae. The bacterium is most commonly spread through person-to-person contact. Diphtheria can be prevented by a vaccine. Canada has included diphtheria in its infant immunization schedule since the 1930's. The success of this program led to a dramatic decline in the number of cases, with very few occurring in Canada since the early 1950s. The National Advisory Committee on Immunization (NACI) recommends immunization against diphtheria.
Diphtheria is caused by the bacterium Corynebacterium diphtheriae.
Some persons infected with diphtheria do not look or feel sick; others develop a sore throat, fever and chills and have difficulty swallowing within 2 to 5 days of becoming infected. This is followed by the formation of a gray, thick membrane at the back of their nose, mouth and/or throat. Complications of the disease include suffocation, paralysis, heart failure, coma and death. One in 10 people with diphtheria die.
An infected person can transmit diphtheria to others until the bacteria disappear from their discharges or lesions. This usually takes between 2 and 4 weeks with the proper antibiotic treatment. Chronic carriers do exist.
The infection is spread by direct contact with an infected individual, as well as by the airborne droplet spread of discharge from the nose or throat of an infected person. Transmission by way of clothing or bedding soiled with nose or throat discharge is rare. Raw milk has also been implicated as a vehicle of transmission.
The number of diphtheria cases is highest during the colder months in temperate zones. In the tropics, seasonal trends are less distinct. In North America, vaccination has greatly reduced the incidence of diphtheria; however, diphtheria was a major problem in countries of the former Soviet Union during the 1990s, with over 150,000 cases and 4500 deaths reported during 1990-1995.
Diphtheria can be prevented by immunization.
For further information about the immunization, please refer to the most recent version of the Canadian Immunization Guide.
Routine immunization against diphtheria in infancy and childhood has been widely practiced in Canada since 1930. In 1924, there were 9,000 cases reported, the highest annual number recorded in Canada. Moreover, diphtheria was one of the most common causes of death in children from 1 to 5 years of age. By the mid-1950s, routine immunization had resulted in a remarkable decline in the morbidity and mortality of the disease. Toxigenic strains of diphtheria bacilli are detected each year, although classic diphtheria is rare. In Canada, there are 0 to 5 isolates reported each year (see Figure 1 ).
Serosurveys of healthy adult populations in Canada indicate that approximately 20% of those surveyed (higher in some age groups) do not have protective levels of antibody to diphtheria. In the former Soviet Union, before the diphtheria outbreak, serologic studies during the 1980s had revealed diphtheria susceptibility rates between 19% and 66% among adults 20 years and older (Dittman et al., 2000).
In Canada, national surveillance data on diphtheria are collected through the Canadian Notifiable Disease Surveillance System (CNDSS).
The following two tables contain recent data on the number of reported cases and incidence of diphtheria in Canada from 2005 to 20110. Data for 2009 and 2010 to 2011 are preliminary. For further surveillance data, please see the Notifiable Diseases On-Line webpage as well as the Publications section below.
|Year||All Ages||Less than 1||1 to 4 years||5 to 9 years||10 to 14 years||15 to 19 years||20 to 24 years||25 to 29 years||30 to 39 years||40 to 59 years||60 years or Greater||Age Unspecified|
|Year||All Ages||Less than 1||1 to 4 years||5 to 9 years||10 to 14 years||15 to 19 years||20 to 24 years||25 to 29 years||30 to 39 years||40 to 59 years||60 years or Greater|