Meningitis: the different types to know

Meningitis: a general definition

We group together under the term meningitisinflammation of the meninges, these membranes that surround the brain and spinal cord (which make up the central nervous system), and cerebrospinal fluid. Meningitis often results froman infection, which may be related to a virus (this is called viral meningitis), to a bacterium (bacterial meningitis) or even a fungus or a parasite.

The clinical manifestations, signs and symptoms of meningitis vary quite little, whether it is viral or bacterial meningitis.

They usually start suddenly, with meningeal syndrome (stiff neck, lethargy, sensitivity to light also called photophobia, disturbance of consciousness, coma or seizure), associated with an infectious syndrome, with a strongfever, violent headaches, nausea, vomiting … 

Symptoms that are not always obvious in the baby

Note that in young children or even in adolescents, the symptoms are sometimes less specific. Some present convulsions especially in cases of bacterial meningitis.  

In infants, a high fever sudden onset should be considered as a warning sign and prompt urgently consult, especially if it is accompanied by unusual behavior, incessant crying, a lethargic state close to unconsciousness.

Bacterial meningitis

Pneumococcal meningitis

Pneumococcus, or Streptococcus pneumoniae, is a family of bacteria that can cause many types of infections, from pneumonia to ear infections to sinusitis. More rarely, pneumococci can cause meningitis, generally following an affection of the ENT sphere (otitis media, cold, etc.). The very old and infants under one year of age are particularly at risk, as are those who are immunocompromised.

Note that there is today a vaccine against pneumococcal infections, which includes 13 bacterial serogroups, and which is one of the 11 compulsory vaccines in infants. This vaccine is administered in three doses: at the age of 2 months, 4 months and 11 months.

Meningococcal meningitis, caused by the bacteria Neisseria meningitidis

Meningococcal bacteria Neisseria meningitidis mainly causes meningitis, and turns out to be the only family of bacterial species capable of causing meningitis epidemics. There are 13 strains, or serogroups, of this family of bacteria. Let us mention in particular meningococcal meningitis type B and type C, the most common in Europe, as well as the A, W, X and Y strains.

In France in 2018, according to data from the National Reference Center for Meningococci and Haemophilus influenzae from the Institut Pasteur, among the 416 cases for which the serogroup was known, 51% were serogroup B, 13% C, 21% W, 13% Y and 2% rare or non-serogroupable serogroups. 

Note that the bacteria Neisseria meningitidis is naturally present in the ENT sphere (throat, nose) in 1 to 10% of the population (outside the epidemic period), according to the World Health Organization (WHO). This bacterium sometimes overwhelms the immune system and triggers meningitis, especially in infants, young children, adolescents or young adults, and immunocompromised people.

Meningococcal contamination occurs during close contact with a carrier individual, via oral secretions (saliva, cough, postilions). Infection by this bacterium can then be limited to the ENT sphere or, in the event of insufficient immune defenses, especially in the absence of a vaccine, diffuse into the bloodstream and reach the meninges.

Which vaccine against meningococcal meningitis?

 There are currently vaccines against several types of meningococcus, but not all: 

• meningococcal type C vaccine, compulsory, administered in two doses at 5 and 12 months, or in a single dose from the age of 12 months and up to the age of 24 years, for those who have not received previous primary vaccination.
• type B meningococcal vaccine called Bexsero, which is recommended and reimbursed only in certain specific situations, in particular in fragile people at risk or in an epidemic situation. ;
• tetravalent meningococcal conjugate vaccine against serogroups A, C, Y, W135, also recommended in specific situations.

Listeria meningitis

While most often mild in a healthy adult, infection with the bacteria Listeria monocytogenes, called listeriosis, can cause symptoms and complications in babies, toddlers, pregnant women and immunocompromised patients. It can then lead to meningitis. Hence the importance of respecting dietary and hygiene recommendations during pregnancy and early childhood, among other things by avoiding raw milk cheeses, raw, smoked or undercooked meat, etc.

Haemophilus influenzae and Escherichia coli, other bacteria involved

Meningitis Haemophilus influenzae (Hib) was still a few decades ago very common in children under five. the vaccine againstHaemophilus influenzae, first advised and then made compulsory, has reduced the incidence of this type of meningitis, and pneumonia caused by this bacteria.

Note that there is also meningitis linked to the bacteria Escherichia coli, which can be transmitted through food or to newborns during childbirth, due to contact with the genital sphere of their mother. Low birth weight babies and premature babies are most at risk, and this meningitis is very serious. Infected toddlers often have brain damage.

Viral meningitis

Meningitis can be of viral origin, in other words due to a virus. In viral meningitis, meningeal syndrome, which groups together various symptoms (headache, photophobia, nausea and vomiting) predominates. Although it can be impressive, viral meningitis is generally benign and its outcome is often favorable.  

Viral meningitis is most often caused by viruses of the enterovirus family (such as Echovirus or Coxsackie virus), but they can also occur following other viral infections such as chickenpox, measles, mumps (in unvaccinated or unimmunized populations), shingles, HIV infection or herpes (especially in immunocompromised people).

Apart from an immune deficiency, healing takes place spontaneously in a few days, and without sequelae.

When faced with a child presenting symptoms of meningitis, as it is not possible by a clinical examination to differentiate viral meningitis from its bacterial form, consultation or even hospitalization is recommended. A lumbar puncture and blood tests will help refine the diagnosis.

Note that enteroviruses likely to cause viral meningitis are transmitted by direct or indirect contact with saliva, sputum, nasal mucus or feces. Also, toddlers and young children, who put toys in their mouths and share their cutlery, are particularly susceptible to becoming infected with each other. Adults who come into contact with affected toddlers can also contract the disease.

Fungal or parasitic meningitis, much rarer

There are very rare cases of meningitis due to fungi (yeasts, Histoplasma capsulatum, Cryptococcus neoformans, Candida albicans ou Candida spp. in particular), or fungal meningitis, and meningitis linked to a parasite, in particular that of toxoplasmosis.

These rare meningitis most often appear in immunocompromised people, especially those whose immune system is severely weakened by AIDS, cancer, anti-rejection treatment following a transplant, etc., and in premature babies with very low birth weight. Treatment is then based on taking antifungal drugs.

sources:

• https://www.pasteur.fr/fr/centre-medical/fiches-maladies/meningites-meningocoques
• https://www.ameli.fr/assure/sante/themes/meningite-aigue/definition-causes-facteurs-favorisants
• https://www.associationpetitange.com/meningites-bacteriennes.html
• https://www.meningitis.ca/fr/Overview