Meningitis Epidemiology and Prevention

Study Notes

Meningococcal Meningitis

Meningococcal meningitis is a serious infection that causes acute inflammation of the meninges surrounding the brain and spinal cord, leading to death if not treated quickly.
The disease is distributed worldwide, but the highest burden is in the meningitis belt of Sub-Saharan Africa (between 5 and 15 degrees north of the Equator).

Epidemiologic Features

The agent is N. meningitidis, a gram-negative diplococci that is delicate and fragile, dying rapidly outside the body and on exposure to heat and cold.
There are several invasive serotypes (IMD), including A, B, C, 29E, X, W-135, and Y, based on capsular polysaccharide antigens.
Carriers are the most important source of infection, with 4-35% of the normal population harboring the organism in the nasopharynx during interepidemic periods.
The carrier rate may increase to 70-80% during epidemics.

Age and Sex

The disease predominantly affects children and young adults of both sexes, with the highest attack rate in infants aged 3-12 months.

Period of Communicability

Cases are infectious until meningococci are no longer present in discharges from the nose and throat, but rapidly lose infectiousness within 24 hours of specific treatment.

Immunity

All ages are susceptible, with younger age groups more susceptible due to lower antibody levels.
Immunity is acquired through subclinical infection, clinical disease, or vaccination, and infants derive passive immunity from their mothers.

Environmental Factors

Seasonal variation is well established, with outbreaks occurring more frequently in the dry and cold months of the year.
Overcrowding, such as in schools, nurseries, universities, army camps, prisons, public transportation, shelters, and crowded poorly ventilated residential places, contributes to the spread of the disease.

Mode of Transmission

The disease spreads mainly by droplet infection through close contact, with the naso-pharynx as the portal of entry.

Incubation Period

The incubation period varies from 2-10 days, with a shorter period of 3-4 days during epidemics.

Clinical Course

Most infections do not cause clinical disease, with many infected people becoming asymptomatic carriers.
Symptoms include sudden onset of intense headache, fever, nausea, vomiting, photophobia, stiff neck, and confusion.

Outcomes/Fatality

The disease is fatal within 24-48 hours in 5-10% of cases even with prompt antimicrobial treatment in good healthcare facilities.
Among survivors, up to 15-20% have permanent neurological sequelae.

Laboratory Confirmation

Lumbar puncture should be done to examine cerebrospinal fluid before starting antibiotics.
High cerebrospinal fluid pressure is a sign of meningitis, and turbidity indicates a bacterial infection.

Prevention and Control

Good ventilation, especially in crowded places, and spreading health awareness among young school students can help prevent the spread of the disease.
Focus should be on surveillance for early diagnosis and individual treatment of cases during an epidemic.
Antibiotics can save the lives of 95% of patients if started during the first 2 days of illness, with penicillin as the drug of choice.

Carriers and Contacts

Carriers require more powerful antibiotics such as rifampicin to eradicate the carrier state.
Close contacts of persons with confirmed meningococcal disease are at an increased risk of developing meningococcal illness, and treatment should be started within 24 hours of identification of the index case.

Description

This quiz covers the epidemiology of meningitis, including the size of the problem, determinants, and measures of prevention and control. It is designed for students of the Faculty of Medicine at Merit University.