Meningococcal meningitis is caused by the Gram-negative bacterium Neisseria Meningitidis. This bacterium causes significant morbidity and mortality in children and young adults worldwide through epidemic or sporadic forms of meningitis and/or septicemia. Meningococcus shares about 90% at the nucleotide level with N. gonorrhoeae or N. lactamiea, and the virulence of the bacterium is influenced by multiple factors. It is a fastidious bacterium that dies within hours on inanimate surfaces and is an encapsulated aerobic diplococcus. At least 13 distinct meningococcal groups have been defined on the basis of their immunological reactivity and capsule polysaccharide structure. These serogroups are: A, B, C, E-29, H, I, K, L, W-135, X, Y, Z and Z '(29E). However, only six serogroups (A, B, C, W-135, X, Y) cause life-threatening diseases.
Meningitis is a disease that is transmitted from infected person to healthy person by the respiratory route, through droplets of saliva and nasal secretions, dispersed while talking or through coughing and sneezing. Meningococcus has evolved multiple mechanisms to be able to transmit, adapt to, and colonize the mucosal surfaces of the predominantly human upper respiratory tract.
Bacterial meningitis is the most frequent form of CNS (Central Nervous System) infection, with a variable annual incidence. The worldwide incidence varies greatly in relation to geographic areas. Approximately 500,000 to 1,200,000 invasive meningococcal diseases occur annually, with 50,000 to 135,000 deaths. In Italy and Europe, most cases of meningococcal meningitis are mainly attributable to serogroup B and serogroup C, although serogroup Y has also increased in recent years. Serogroups A and W135 are prevalent in the rest of the world, especially in sub-Saharan Africa. Serogroup A was the main agent of invasive meningococcal disease in Europe before and during World Wars I and II, while serogroup B has been prevalent since 1970 in Europe and since 1980 in South America. Epidemic outbreaks due to serogroups W-135 and Y have emerged more recently during the 21st century. In addition, there has been a change in the age groups affected by invasive disease, with an increase in the incidence of serogroup Y in the elderly and a decrease in serogroup C in adolescents. The epidemiological trend of invasive disease has remained virtually unchanged in Africa, where serogroup A is still the most prevalent with an annual incidence open to 10-20 cases per 100,000 population. Epidemic outbreaks occurring during the dry season imply an attack rate of more than 1,000 cases per 100,000; very recently, serogroups X and W-135 have had a major impact in terms of morbidity and mortality. In Australia, the incidence of meningococcal disease is above 3 cases per 100,000 population. In most American and European countries, there is generally a low level of endemicity. In 2011, 29 European countries reported 3,808 confirmed cases of invasive disease. The incidence of invasive disease borne by serogroup B in Europe accounted for 0.5 cases per 100,000 inhabitants. Italy reports the lowest incidence rate of 0.25 cases per 100,000.
Generally, the incubation period of meningococcal meningitis is 3 to 4 days, but it can vary from 2 to 10 days.
Meningitis initially manifests with nonspecific symptoms such as fatigue, drowsiness, asthenia, and headache. After about 3 days, the symptom picture tends to worsen with manifestations of nausea, vomiting, fever, photosensitivity, and characteristic nuchal stiffening.
The infection can progress to three clinical pictures: sepsis (meningococcemia), meningitis, and sepsis with meningitis.
Meningococcemia is observed as an isolated picture in 10-30% of patients in the absence of signs and symptoms of meningitis. Meningitis represents the most frequent clinical presentation and is characterized by the appearance of high fever, headache, nuchal rigidity, photophobia, and altered mental status. Meningococcal infection may also be responsible for pericardial infection, and the appearance of purulent or immune complex arthritis, conjunctivitis, panophthalmitis, and urogenital tract infections is possible.
In infants, symptoms may not be very obvious and are manifested by continuous crying, irritability, and inappetence.
In addition to the detection of typical symptoms, diagnosis is based on laboratory tests. After performing hemoculture, it is necessary to perform lumbar puncture for examination of cerebrospinal fluid. The use of polymerase chain reaction (PCR) on blood or CSF may allow more rapid identification of the responsible microorganisms.
Primary prevention is based on the meningitis B vaccine and the meningitis A,C,W,Y vaccine administered preventively. Several types of meningitis vaccines are available in Italy, which are also recommended by the National Vaccination Plan. Each of us in the course of our lives comes into contact at least once with the meningitis bacterium. To develop the disease, however, is a relatively small percentage (about 200 people a year) compared to the thousands and thousands of healthy carriers. Anyone can contract meningococcal disease, but certain groups of people have a higher risk. The meningitis vaccine is the most effective preventive strategy for the entire population, with a special focus, however, on the most vulnerable, such as children and adults with compromised immune systems. The Vaccine Calendar strongly recommends that children be vaccinated for meningococcal B and meningococcal C during the first few years of life, as they have immune systems that are not yet fully mature, and transmission is facilitated by the type of very intense social contact. Other individuals elective for vaccination are adults with diseases that weaken the immune system, such as genetic diseases, oncohematology, diabetes, or who are on immunosuppressive therapy. Those who work in settings where transmission of the bacterium is favored, such as health care workers and teachers, are also indicated to receive the meningitis vaccine. Although meningococcal disease is widespread globally, the "meningitis belt" of sub-Saharan Africa has the highest rates in the world. Travelers who spend a lot of time with local people in the meningitis belt, especially during outbreaks of meningococcal disease (December to June), have the highest risk of contracting the disease. Those participating in the Hajj pilgrimage in Saudi Arabia are also at higher risk, so preventive meningitis vaccine is required by the country's National Authorities.
In addition to vaccination, remember the normal rules of good hygiene:
- Wash your hands often
- If soap and water are not available, clean hands with a hand sanitizer (containing at least 60 percent alcohol)
- Do not touch eyes, nose or mouth with unwashed hands
- Cover the mouth and nose with a handkerchief or sleeve (not the hands) when coughing or sneezing
- Try to avoid contact with sick people.
Contact surveillance
Contact surveillance is the strategy outlined by Health Authorities to control infections and possible epidemic outbreaks. It consists of tracking, identifying and possibly treating contacts, considered significant, of the index case, i.e., the sick person. Careful assessment must be carried out depending on the individual case, but generally for the identification of a close contact is considered:
- Cohabitants (also considering the same classroom or shared office/enclosed space)
- Who has often slept or eaten in the same place as the sick person
- Who in the days before the onset of symptoms had contact with the sick person's saliva, such as through kissing or dishes
- health care personnel directly exposed to respiratory secretions.