Meningitis is the inflammation of the meninges, the lining that surrounds the brain and spinal cord.
Meningitis can be caused by fungal, viral, bacterial, and parasitic infections, by cancerous processes, and by chemical reactions to intrathecal injections.
The most common types of meningitis are bacterial, caused by Haemophilus influenzae type b (Hib) infection and by Neisseria meningitidis (groups A, B, C, Y, W-135), also known as meningococcus.
There may be other causative bacteria, but they are less representative due to their frequency in epidemics.
Although viral or aseptic meningitis is the most common in children, bacterial meningitis is the one that causes more deaths, in addition to leaving lifelong neurological sequelae. Therefore, global efforts have focused on creating vaccines to prevent these infections.
Meningitis primarily affects children aged 3 to 8 months and its incidence can reach 1 per 100,000 inhabitants. More than half of those affected are under 15 years of age.
The frequency of epidemic causes is:
There is an increased risk of infection in people with complement factor deficiencies (C3, C5-C9), in people without a spleen, or in those affected by HIV (in these cases, infection by serotype A has been particularly increased).
In military service, epidemics of serotype C have been increased, therefore in the USA, meningitis vaccine against groups A, C, Y, W-135 is administered as prevention.
Meningitis is transmitted through nasal secretions, saliva, and contaminated air from sneezing or coughing by affected patients. This means that contact must be close for transmission to occur.
Except in cases of compromised immune defenses due to previous diseases (lymphomas, immunodeficiencies, diabetes, etc.), susceptibility is low, since the causative bacteria is usually present in the throat of 10% of individuals without developing the disease.
The disease develops following intense contact with bacteria from the secretions of an individual affected by meningitis.
The most frequent symptoms are:
And the most dangerous symptoms are:
In a person with the described symptoms, the infection must be confirmed through examination of cerebrospinal fluid (CSF) obtained by lumbar puncture.
Some findings in this examination such as turbid appearance, increased cell count, and decreased glucose suggest a diagnosis of bacterial meningitis.
A presumption of the causative bacteria can be made with Gram staining, but a confirmatory bacterial culture is always performed to determine with certainty both the pathogen and the antibiotics that can be used in treatment.
Other tests such as blood analysis and radiological imaging may be performed to rule out other diagnoses or when complications such as brain abscess are suspected.
Meningeal infection develops 2 to 10 days after contact with the infected person, with the previously indicated symptoms appearing and must be treated within 24-36 hours. During this period the disease can be fatal.
Mortality in these cases reaches 1 in every 7 affected individuals, and with appropriate treatment within 24 hours it can be reduced by 10%.
Immediate complications are usually very serious: seizures, shock, coagulation disorders and cardiorespiratory arrest.
Despite recovery, the person may present neurological sequelae, most frequently sensorineural hearing loss.
Since this is a disease that can seriously compromise life, hospitalization of the person with bacterial meningitis is sought as soon as possible.
In the hospital, oxygen and intravenous fluids will be administered and an antibiotic protocol will be initiated while cerebrospinal fluid culture results are obtained.
Despite adequate treatment, up to 16% of people are left with sequelae that require follow-up by neurology and rehabilitation specialists.
A Neisseria meningitidis group C meningitis epidemic is considered when 3 cases appear in a community in less than three months and the total prevalence is more than 10 cases per 100,000 inhabitants, and ONLY in this case is widespread vaccination recommended.
The main form of prevention of bacterial meningitis is vaccination against Neisseria meningitidis (meningococcus) and Haemophilus influenzae type b (Hib).
In cases of previous complement pathway disorders and absence of spleen, meningitis vaccine is always indicated (groups A, B, C, Y, W-135).
If there is an epidemic (10 cases per 100,000 inhabitants), vaccination of children is indicated.
Protective measures or prophylaxis should be implemented in case of:
Chemoprophylaxis is effective in the first days of contagion, and no more than 15 days after. Pharyngeal swab cultures are not useful due to the delay in results relative to the effective period.
In cases of close contact with those affected by meningococcus (Neisseria meningitidis), prophylaxis with rifampin is indicated, and ceftriaxone and ciprofloxacin can be used as alternatives.
In cases of close contact with those affected by Haemophilus influenzae type b (Hib), prophylaxis with rifampin is performed.
Rifampin should not be used in pregnancy, and it interacts with contraceptives so they may fail.
Improving hygiene reduces the spread of the epidemic. Additionally, paper tissues should be used to cover coughs or sneezes of possibly affected individuals.
Currently there are three vaccines available against meningococcus:
MenC vaccine (vaccine against Neisseria meningitidis C).
The MenC vaccine protects against Neisseria meningitidis bacteria of serogroup C. It is a conjugate vaccine derived from meningococcus C polysaccharide capsule conjugated to a protein. When injected in humans it produces immunity for meningitis C from 2 months of age.
Side effects:
MenACWY vaccine (vaccine against Neisseria meningitidis A, C, W, Y).
The vaccine for meningitis caused by Neisseria meningitidis group A, C, Y, W-135, is administered by injection in a single subcutaneous dose of 0.5 ml, containing 50 g of capsular polysaccharides from each serotype of Neisseria meningitidis.
As side effects, local inflammation and some fever may be observed.
Protective effects begin at 7-10 days.
Its efficacy is good (not complete) in children over 2 years old. In children from 3 months to 2 years it is of doubtful efficacy (does not provide coverage), and it is not indicated in those under 3 months. (Serotype A may produce antibodies in children from 3 months of age but not comparable to the level achieved from 5 years of age. Serotype C is poorly effective before 2 years of age).
Meningococcus B vaccine
After vaccination against other types of meningococcus became widespread, type B turned out to become the most frequent, which is why mass vaccination against it has also begun.
Its administration is recommended at two months of age.
| Efficacy over time after vaccination | ||
|---|---|---|
| Age | First year | Third year |
| Under 4 years | 90% | < 10% |
| Over 4 years | 95% | 67% |
The level of antibodies against serotypes A and C decreases in the first three years after a single dose, this antibody decline is faster in children than in adults. Its protective effect lasts 1 to 3 years depending on age and no longer.
It is recommended in cases with risk factors (immunodeficient, convalescent, immunosuppressed, splenectomized patients, etc.) in addition to laboratory personnel with exposure to Neisseria meningitidis.
It can be administered simultaneously with other vaccinations without problems.
The vaccine contains Thiomersal, so care should be taken in those allergic to mercurial antiseptics or phenol.
In Spain, one dose of the MenC vaccine is administered at 4 months of age and a booster dose at 12 months (either the MenC vaccine or the MenACWY vaccine depending on the autonomous community). Finally, at 12 years of age, one dose of the MenACWY vaccine is administered.
It can be administered without problems for the mother or child, producing high levels of antibodies in the newborn that disappear quickly in the first months. Therefore, vaccination schedules should not be altered for having done so during pregnancy.
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