Meningococcal Disease

Epidemiology of Infectious Disease: Meningococcal Disease

Causal agent
Meningococcal meningitis and meningococcal septicaemia are systemic infections caused by the bacteria Neisseria meningitidis. The infection may present as meningitis, septicaemia or a combination of both¹.

Meningococci are divided into at least 13 distinct serogroups. The most common are serogroups A, B, C, Y and W135. Most disease in the UK is caused by group B.  

Common clinical features

• The early symptoms are non-specific and are often mistaken for a viral infection¹.  
• Meningococcal infection progresses rapidly, with the clinical picture changing hourly¹.
• In infants symptoms can include the sudden onset of fever, floppiness, high-pitched crying, neck retraction with arching of the back and sometimes vomiting. In infants there is progressive irritability, altered consciousness and sometimes convulsions¹.
• Common symptoms in children and adults can include the sudden onset of fever, malaise, increasing headache, nausea, photophobia, neck stiffness and often vomiting.
• In meningococcal septicaemia, a rash may develop along with signs of advancing shock and isolated limb and/or joint pain. The rash may be non-specific early on but as the disease progresses the rash may become petechial or purpuric and may not blanch³.
• Meningococcal sepsis occurs without meningitis in 5-10% of invasive meningococcal infections.
• Meningococcal disease has a case fatality rate of approximately 10%, in the UK. Case fatality ratios increase with age and is higher in those with septicaemia than in those with meningitis alone³.
• Of patients who recover 11-19% develop permanent sequelae, including hearing loss, brain damage, seizures and loss of limb.

Epidemiology

• Endemic worldwide.
• The highest burden of meningococcal disease occurs in sub-Saharan Africa (the Meningitis Belt) an area from Senegal in the West to Ethiopia in the east where high rates of sporadic infections occur in annual cycles with periodical large scale epidemics².  In 1996, Africa experienced the largest recorded outbreak of epidemic meningitis in history with over 250 000 cases and 25,000 deaths registered.
• N. meningititis A, C and W135 are the main serogroups involved in the meningococcal activity in Africa.
• In 2005 1,462 laboratory confirmed cases of N. meningitidis were reported in England and Wales. The majority of meningococcal infections occur in children under 5 years, with a peak incidence at 6 months of age. There is a smaller, secondary peak in incidence among young adults aged between 15-19 years of age (HPA).
• Meningococcal disease shows a marked seasonal variation with the highest incidence occurring during the winter.
• Most cases of meningococcal disease occur sporadically, with <5% of cases occurring in clusters. Outbreaks are more common among teenagers and young adults and outbreaks have been reported in schools and universities (HPA).
• Since the introduction of Men C vaccine into the UK routine immunisation programme the number of laboratory confirmed group C cases have fallen by over 90% among all age groups immunised. Cases among other age groups have fallen by two-thirds as a result of reduced carriage rates³.
• In the UK serogroup B is now responsible for >85% of laboratory confirmed cases (HPA).

Reservoir
Humans

Mode of transmission

• Person to person, transmitted by droplet aerosol or secretions from the nasopharynx of colonized persons.
• Transmission usually requires either frequent or prolonged close contract.
• Risk factors for the development of disease is not fully understood but may include age, season, smoking, preceding influenza A infection and living in closed or semi-closed communities such as military barracks³.

Incubation period
2-10 days, commonly 3-4 days.

Period of Communicability

• While live meningococci are present in discharges from nose and mouth.
• Meningococci usually disappears from the nasopharynx within 24 hours of appropriate antimicrobial treatment.
• Up to 10% of people may be asymptomatic carriers with nasopharyngeal colonization by N. meningititis. However, less than 1% of those colonized will progress to invasive disease¹.
• High carriage rates of up to 25% have been observed in 15-19 year olds.
• Carriage confers natural immunity.

Treatment
An immediate dose of benzyl penicillin for suspected meningococcal infection should be given^1,4.

Children aged < 1 year - 300mg
Children aged 1-9 years - 600mg
Adults and children aged >10 years - 1200mg

Prevention and control
In the UK immunisation against meningococcal group C is recommended for persons under the age of 25 years and for all first year university students.

Public health action is indicated for confirmed or suspected cases. There are 4 key actions in response to a suspected case as outlined by Hawker et al¹.

1. Ensure rapid admission to hospital and pre-admission benzyl penicillin.
2. Ensure appropriate laboratory investigations are undertaken.
3. Arrange for chemoprophylaxis for close contact and immunisation if infection is due to a vaccine preventable strain.
4. Provide information about meningococcal disease to parents, GPs and educational establishments.

Chemoprophylaxis
Chemoprophylaxis should be offered to close contacts of cases, irrespective of vaccination status⁴.

Close Contacts
Close contact are those who have had prolonged close contact with the case in a household type setting during the seven days before the onset of illness. These include; those living and/or sleeping in the same household (including extended household), pupils in the same dormitory, boy/girlfriends, or university students sharing a kitchen in a hall of residence⁴.

Those who have had transient close contact with a case only if they have been directly exposed to large particle droplets/secretions from the respiratory tract of a case around the time of admission to hospital⁴.

Table 1: Recommended chemoprophylaxis⁴. 

References

1. Hawker J, Begg N, Blair I, Reintjes R, Weinberg J. Communicable Disease Control Handbook, Blackwell, 2005.
    
2. Heymann D L. Control of Communicable Disease Manual. 18^th ed. Washington: American Public Health Association; 2004.
    
3. Salisbury DM, Begg NT.  Immunisation against infectious disease (The green Book). London: HMSO, 1996. Available at http://www.dh.gov.uk/assetRoot/04/07/29/84/04072984.pdf
    
4. PHLS, Meningococcus Forum, Guidelines for public health management of meningococcal disease in the UK, Communicable Disease and Public Health, [serial online] September 2002, 5(3);187-204. Available at: http://www.hpa.org.uk/cdph/issues/CDPHVol5/no3/Meningococcal_Guidelines.pdf

Further Resources

The Meningitis Research Foundation http://www.meningitis.org/

The Meningitis Trust http://www.inmed.co.uk/resources/professionals.html

© CM Kirwan 2006