Pertussis

Pertussis (whooping cough) is a highly contagious infection of the respiratory tract caused by the bacterium Bordetella pertussis. The National Advisory Committee on Immunization (NACI) recommends immunization against pertussis.

About Pertussis

Agent of disease

Pertussis is caused by the Gram-negative aerobic bacterium Bordetella pertussis.

Symptoms

Symptoms begin 6 to 20 days after an individual becomes infected and are characterized by the development of a fever, vomiting and paroxysmal cough (coughing attack), which gets progressively worse. Complications due to pertussis include pneumonia, seizures, brain damage and death. Death is estimated to occur in 1 out of every 200 cases in children < 1 year of age.

Period of communicability

In general, an individual should be considered infectious from the beginning of infection to 3 weeks after coughing begins, if not treated with antibiotics. If the individual receives appropriate antibiotic treatment, the period of communicability is reduced to 5 days after treatment began.

How it is transmitted

The bacterium is transmitted through direct contact with, or inhalation of, the secretions from an infected individual's nose or mouth.

Worldwide distribution

Pertussis is a common disease occurring year round throughout the world. The number of cases in developed countries has dropped dramatically as a result of widespread immunization programs, proper nutrition and good medical care. In Canada, the number of cases increased in the late 1990s likely due to waning immunity. Pertussis is one of the leading causes of death among non-immunized children in developing countries.

Prevention & control

Pertussis can be prevented by immunization. Primary immunization for all children is recommended at 2, 4 and 6 months of age. Booster doses are recommended at 18 months, 4 to 6 years, and 14 to 16 years of age. For further information about the immunization recommendations, please refer to the most recent version of the Canadian Immunization Guide.

Cases should be reported to the local health authority. Confirmed and suspected cases should be isolated from young children and infants until the patients have received at lease 5 days of antibiotics. Suspected cases who do not receive antibiotics should be isolated for 3 weeks after onset of paroxysmal cough or until the end of cough, whichever comes first.

Contacts, especially children, must have their immunization status verified. If immunization status is incomplete and no contraindications are identified, necessary doses of vaccine should be given.

Epidemiology of Pertussis in Canada

Pertussis is a cyclical disease, which peaks at two to five year intervals. With the introduction of the whole-cell pertussis vaccine in 1943, the incidence of pertussis decreased significantly in Canada, from an average of 165 cases per 100,000 population from 1935 to 1939 to a low of 6 cases per 100,000 from 2005 to 2009. As seen in Figure 1 , a resurgence of pertussis was observed beginning in 1990. This was likely due to a combination of factors, including the low efficacy of the combined adsorbed diphtheria-tetanus-pertussis whole-cell vaccine used in children in Canada between 1980 and 1997, waning immunity from the previous vaccine among adolescents and adults, as well as increased physician awareness and improved diagnosis and reporting of pertussis infection. The whole cell vaccines were replaced with acellular vaccines made from purified antigens of B. pertussis in 1997/98 in Canada.

The incidence of pertussis is highest in infants and children, and decreases sharply in those older than 14 years (see Figure 2 ). Average incidence rates from 2005 to 2009 were 86 cases per 100,000 population among infants less than 1 year of age (average of 310 cases per year), 33 cases per 100,000 in children 1 to 4 years (459 cases per year), and 16 cases per 100,000 in children 5 to 9 years (290 cases per year). As seen in Figure 3, an increase in incidence was observed in adolescents and adults due to low vaccine efficacy in the population cohort that was immunized with the vaccine available between 1980 and 1997. As these persons constituted a major reservoir of the disease and were an important source of transmission to infants, in 2003 the National Advisory Committee on Immunization recommended a single dose of the adolescent/adult formulation of the combined diphtheria-tetanus-acellular pertussis vaccine. This was incorporated into vaccine programs across Canada by the end of 2004. Since 2003 the incidence of pertussis has decreased in the 15 to 19 year age group from 18.7 to 2.8 cases per 100,000 population in 2009.

Figure 1. Reported incidence (per 100,000 population) of pertussis in Canada by year, 1924 to 2011*

*Case data obtained from the Canadian Notifiable Disease Surveillance System. Population data obtained from Statistics Canada July 1^st annual estimates. Data for 2009 to 2011 are preliminary.

Figure 1 - Text Equivalent

Figure 2. Reported incidence (per 100,000 population) of pertussis in Canada by year and age group, 1980 to 2011*.

*Case data obtained from the Canadian Notifiable Disease Surveillance System. Population data obtained from Statistics Canada July 1st annual estimates. Data for 2009 to 2011 are preliminary.

Figure 2 - Text Equivalent

Pertussis Surveillance in Canada

In Canada, surveillance of pertussis is through two systems at the national level: Canadian Notifiable Disease Surveillance System (CNDSS) and the Immunization Monitoring Program, ACTive (IMPACT).

Pertussis Data

The following two tables contain recent data on the number of reported cases and incidence of pertussis in Canada from 2005 to 2011. Data from 2009 to 2011 are preliminary. For further surveillance data, please see the Notifiable Diseases On-Line webpage as well as the Publications section below.

Pertussis Resources

Case Definitions

• Case definitions for Diseases under National Surveillance, 2009
• Case Definitions for Diseases under National Surveillance, 2000

Publications

• 2006 Canadian Report on Immunization (Section 4.7 – Pertussis)
• Pertussis (Whooping Cough) – Fact Sheet

Guidelines and Recommendations

• Statement on the recommended use of pentavalent and hexavalent vaccines, February 2007
• Interval Between Administration of Vaccines Against Diphtheria, Tetanus, and Pertussis, October 2005
• Interchangeability of Diphtheria, Tetanus, Acellular Pertussis, Polio, haemophilus Influenzae Type B Combination Vaccines Presently Approved for Use in Canada for Children <7 Years of Age, February 2005
• Clarification: Prevention of pertussis in adolescents and adults, March 2004
• Prevention of Pertussis in Adolescents and Adults, September 2003
• Statement on Adult/Adolescent Formulation of Combined Acellular Pertussis, Tetanus, and Diphtheria Vaccine, May 2000

Other Resources

• National Consensus Conference on Pertussis
• Proceedings of the National Microbiology Laboratory Pertussis Workshop