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Invasive Meningococcal Disease (IMD)

Invasive meningococcal disease is an acute and serious illness caused by the bacterium Neisseria meningitidis. Invasive disease may lead to meningitis, in which the bacteria infect the fluids and membranes (called meninges) covering the brain and the spinal column, or septicemia. The National Advisory Committee on Immunization (NACI) recommends immunization against meningococcal disease.

About Invasive Meningococcal Disease

Agent of disease

Invasive meningococcal disease is caused by the bacterium Neisseria meningitidis. In Canada, five of its serogroups (A, B, C, W-135, and Y) are responsible for the majority of disease.

Symptoms

The most common form of meningococcal infection is the carrier state, in which a person has the bacteria on the lining of the nose or throat but does not develop symptoms of the disease. A person may remain a carrier of the same strain for up to six months and remain asymptomatic. Invasive disease is a severe form of infection that occurs when the bacterium gets into parts of the body where bacteria are not usually found, such as the bloodstream and the meninges. Invasive meningococcal disease most often results in meningitis or septicemia or a combination of both. Symptoms occur 2 to 10 days (usually 3 to 4 days) after exposure and include the sudden development of fever, drowsiness, irritability or agitation, intense headache, vomiting, stiff neck and a characteristic rash. Severe cases can result in delirium and coma and, if untreated, toxic shock and death.

Period of communicability

A person is capable of passing the infection to others as long as the bacteria are present in discharge from the nose and mouth. The bacteria usually disappear from the nose and throat within 24 hours after appropriate antimicrobial treatment has begun.

How it is transmitted

Spread from an infected person (including carriers) to another person requires close, direct contact such as kissing, coughing and sneezing. It can also be spread through saliva when sharing items such as cigarettes, lipstick, food and drinks, etc.

Worldwide distribution

Meningococcal disease occurs worldwide. In Canada, infection is most common in the winter and spring months. Meningococcal disease most often occurs in children less than five years of age, in males more than females, and more commonly in newly gathered adults living in crowded conditions, such as in barracks and college dormitories. Another peak occurs in adolescents 15 to 18 years of age. Outbreaks of serogroup C were fairly common in the past; between 1999 and 2001, eight outbreaks occurred in Canada. In more recent years, there has been a significant decline in the incidence of serogroup C, likely due to the introduction of meningococcal C conjugate vaccine into routine immunization programs. After serogroup C, serogroup B has caused the second highest burden of disease within Canada. Serogroup A organisms are responsible for most infections in the sub-Saharan region of Africa.

Prevention and control

Invasive meningococcal disease due to infection by serogroups A, C, W-135, and Y can be prevented by immunization. Routine use of monovalent meningococcal vaccine against serogroup C is recommended by NACI for all infants as a part of the routine immunization schedule. A booster dose of either monovalent serogroup C vaccine or quadrivalent vaccine (for protection against serogroups A, C, W-135, and Y) is recommended around the age of 12 years. Additionally, quadrivalent vaccine is recommended for selected individuals at increased risk of acquiring infection. For specific recommendations about meningococcal vaccines and their use, please refer to the most recent Canadian Immunization Guide as well as NACI statements on invasive meningococcal disease. For further information on prevention and control measures, please see the Guidelines for the Prevention and Control of Meningococcal Disease.

Invasive Meningococcal Disease Epidemiology in Canada

Invasive meningococcal disease is endemic in Canada, showing periods of increased activity roughly every 10 to 15 years with no consistent pattern. The incidence rate varies considerably with different serogroups, age groups, geographic locations and time. Implementation of immunization programs has also affected disease epidemiology.

As depicted in Figure 1, from 1985 to 2010 the overall incidence of IMD has ranged between 0.4 to 1.6 cases per 100,000 population. Between 2005 and 2010, an average of 197 cases of IMD was reported annually in Canada, with an average incidence of 0.60 cases per 100,000 population. During this time period, incidence rates were highest among infants less than one year of age (average 6.98 cases per 100,000), followed by 1 to 4 year olds (1.81), and 15 to 19 year olds (1.18).

As seen in Figure 2, the majority of reported cases were due to serogroup B (59%), for which there is currently no vaccine program in Canada. From 2005 to 2010, serogroup B incidence has remained relatively stable at 0.27 to 0.40 cases per 100,000 population per year (average of 110 reported cases per year, range 92 to 131). Serogroup B disease has tended to affect infants, children, and adolescents (median age 16 years, range 0 to 95).

Due to localized outbreaks of serogroup C, IMD incidence peaked in 1990 and then again in 2001. Immunization campaigns using serogroup C polysaccharide and conjugate vaccines were implemented in several Canadian regions during outbreaks from 1999 to 2001. Between 2002 and 2007, all Canadian provinces and territories implemented routine conjugate serogroup C vaccination programs. By 2011, half of them had also implemented routine conjugate quadrivalent (ACW135Y) programs. Since the last peak in 2001, serogroup C incidence has decreased. From 2005 to 2010, serogroup C incidence ranged from 0.03 to 0.13 cases per 100,000 population (average of 29 reported cases per year, range 11 to 43). Serogroup C tends to affect older adults (median age 38 years, range 0 to 96).

Like serogroup B, serogroup Y incidence has remained relatively stable, ranging from 0.07 to 0.11 cases per 100,000 population per year from 2005 to 2010 (average of 31 reported cases per year, range 24 to 37). Unlike serogroup B, serogroup Y has tended to affect older adults (median age 44 years, range 0 to 97). Serogroup W-135 only accounted for 6% of cases, with an average incidence of 0.03 cases per 100,000 from 2005 to 2010. About 11 serogroup W-135 cases were reported each year during that time. Cases caused by other serogroups (including A, 29E, X, and Z) remain rare in Canada (15 cases reported in total between 2005 and 2010).

From 2005 to 2010, 6.7% of reported IMD cases died. Case fatality ratios differed by serogroup, with serogroup C having the highest at 13.0% and B having the lowest at 4.8%.

Figure 1. Reported cases and incidence (per 100,000) of invasive meningococcal disease in Canada, 1985 to 2010*.

Figure 1. Reported cases and incidence (per 100,000) of invasive meningococcal disease in Canada, 1985 to 2010*.

*Case data obtained from the National Enhanced Invasive Meningococcal Disease Surveillance System. Population data obtained from Statistics Canada July 1st annual estimates. Data for 2007 to 2010 are preliminary.

Figure 1 - Text Equivalent


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Figure 2. Incidence of invasive meningococcal disease per 100,000 population in Canada by serogroup and year, 1995 to 2010*.

Figure 2. Incidence of invasive meningococcal disease per 100,000 population in Canada by serogroup and year, 1995 to 2010*.

*Case data obtained from the National Enhanced Invasive Meningococcal Disease Surveillance System. Population data obtained from Statistics Canada July 1st annual estimates. Data for 2007 to 2010 are preliminary.

Figure 2 - Text Equivalent

Invasive Meningococcal Disease Surveillance in Canada

In Canada, surveillance data on IMD is collected through three systems at the federal level:

Invasive Meningococcal Disease Data

The following two tables contain recent data on the number of reported cases and incidence of invasive meningococcal disease in Canada from 2005 to 2011. Data for 2008 to 2011 are preliminary. Numbers obtained from this system may be slightly different from those obtained from the Canadian Notifiable Disease Surveillance System. For further surveillance data, please see the Notifiable Diseases On-Line webpage as well as the Publications section below.

Table 1. Reported cases of invasive meningococcal disease in Canada by year and age group, 2005 to 2011.
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

*Data obtained from the National Enhanced Invasive Meningococcal Disease Surveillance System.
†Based on preliminary data.
2005* 182 17 24 14 13 26 25 6 10 23 24 0
2006* 212 27 25 8 9 31 28 6 18 27 32 1
2007* 229 25 27 14 7 29 21 12 11 45 36 2
2008*† 195 26 23 4 9 27 16 8 9 39 34 0
2009*† 209 40 34 9 7 23 14 7 8 34 33 0
2010† 154 18 22 2 5 22 15 5 8 36 21 0
2011† 171 25 34 4 7 23 11 6 6 20 35 0
Table 2. Reported incidence per 100,000 population of invasive meningococcal disease in Canada by year and age group, 2005 to 2011.
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

*Data obtained from the National Enhanced Invasive Meningococcal Disease Surveillance System.
†Based on preliminary data.
2005* 0.56 5.01 1.75 0.75 0.61 1.19 1.12 0.28 0.22 0.24 0.42 0.00
2006* 0.65 7.71 1.81 0.44 0.43 1.40 1.24 0.27 0.40 0.27 0.54 0.00
2007* 0.70 6.94 1.92 0.78 0.34 1.30 0.92 0.54 0.24 0.45 0.59 0.01
2008*† 0.59 6.97 1.61 0.22 0.45 1.20 0.70 0.35 0.20 0.39 0.53 0.00
2009*† 0.62 10.53 2.32 0.50 0.35 1.02 0.60 0.30 0.18 0.34 0.50 0.00
2010† 0.45 4.70 1.46 0.11 0.26 0.99 0.63 0.21 0.17 0.36 0.31 0.00
2011† 0.50 6.49 2.21 0.22 0.37 1.05 0.46 0.25 0.13 0.20 0.50 0.00

Invasive Meningococcal Disease Resources

Case Definitions

Publications

Guidelines and Recommendations

Other Resources

Date Modified: 2012-07-23

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