Causative Agent
Neisseria meningitidis is the bacteria responsible for causing meningococcal infection. It is classified according to its outer membrane characteristics in a process known as serogrouping. There are a number of different serogroups, the most common of which in Scotland and the UK is serogroup B. Following the introduction of a vaccine to protect against meningococcal serogroup C disease in 1999, serogroup C is now rarely observed in Scotland. Sero-groups Y, W135, and 29E are observed at low levels.
Clinical Description
Meningococcal disease refers exclusively to invasive infections of N. meningitidis from blood, cerebrospinal fluid (CSF) or other sterile site. Approximately, 80% of meningococcal disease cases present with meningitis, an inflammation of the meninges (meningitis can be caused by a variety of viruses or bacteria, of which N. meningitidis is one), while the remaining cases present with septicaemia (blood poisoning).
Transmission
Approximately 10% of the population are estimated to carry N. meningitidis in the nasopharynx, the vast majority of which remain asymptomatic. Invasive cases acquire their infection from asymptomatic carriers following the release of respiratory droplets.
Surveillance in Scotland
A scheme of enhanced surveillance was introduced in 1999 and is managed jointly
by HPS and the Scottish Meningococcus & Pneumococcus Reference Laboratory
(to which all hospitals in Scotland send their samples). This information is
used to monitor trends in notfifications and faciliates more complex analyses
involving age, serogroup, outcome etc.
Prevention
The MenC vaccine is included in the UK Childhood Immunisation schedule, with routine vaccination recommended at three and four months followed by a booster between 12 and 13 months of age. MenC vaccine only prevents against serogroup C disease.
N. meningitidis does not survive long outside the body, therefore prolonged and close contact with an infected individual who is either ill or a carrier is required to transmit these bacteria. Antibiotics and vaccination (depending on the serogroup) are recommended for close contacts of a case in order to prevent further spread from potential carriers.
Surveillance in Scotland
A scheme of enhanced surveillance (Meningococcal Invasive Disease Augmented Surveillance, MIDAS) was introduced in 1999 and is managed jointly by Health Protection Scotland and the Scottish Haemophilus Legionella Meningococcus and Pneumococcus Reference Laboratory (SHLMPRL). This information is used to monitor trends in notifications and facilitates more complex analyses involving age, serogroup, molecular typing, clinical presentation and outcome.
Notification
Meningococcal disease is a notifiable disease under the Public Health etc. (Scotland) Act 2008.
Trends in Scotland (1995-2010)
Notifications of meningococcal infection remained fairly stable from 1977 until the mid 1990s, with between 100 and 200 cases reported per year. An increase was noted in 1997 and continued throughout 1998 and 1999. An unusually large influenza outbreak in the 1999/2000 winter period is thought to have contributed to the continuation of this increasing trend.
Historically, the predominant serogroup causing meningococcal disease in Scotland has oscillated between serogroup B and C infection. In the year prior to the introduction of the MenC vaccine (November 1999), serogroup C was responsible for causing more infection than serogroup B. Following the introduction of the vaccine, year-on-year decreases in overall case numbers from all serogroups have been observed. However, no cases of serogroup C disease have been reported in Scotland since 2007 indicating the effectiveness of the MenC vaccine campaign.
Between 100 and 150 cases of meningococcal disease are now detected in Scotland each year, with the majority of cases in children and young adults. Case fatalities due to meningococcal infection continue to occur, with between five and ten deaths reported each year (a case fatality rate from 2-5%). The majority of deaths are in people over the age of 16 with serogroup B infection.
A high index of suspicion, early detection and treatment provide the best opportunity to reduce the impact of this disease.
Meningococcal Infections Cases, in Scotland, by Year, 1999 - 2010
| Year |
Number of Cases |
1999 |
350 |
2000 |
355 |
2001 |
271 |
2002 |
195 |
2003 |
155 |
2004 |
150 |
2005 |
145 |
2006 |
143 |
2007 |
156 |
2008 |
125 |
2009 |
139 |
2010 |
99 |
| |
|
Meningococcal disease cases in Scotland, by age group and quarter, 2001-2011*
Meningococcal disease cases by serogroup, 1999-2011*
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