What is Meningitis?
Meningitis is a severe disease caused by microbial infection of the fluid (cerebrospinal fluid) found in the protective layers surrounding the brain and spinal cord (meninges), leading to inflammation and swelling, along with a host of other symptoms. Meningitis is considered a major public health threat and has a cosmopolitan distribution, meaning that it occurs in various parts of the world and is not endemic to a particular region. The disease can occur in a range of situations, from individual infections to small clusters and even widespread epidemics, with a fatality rate as high as 50% when left untreated. The disease affects people of all ages, but some forms are more prevalent in children.
What causes Meningitis?
The disease is caused by a variety of infectious microorganisms, ranging from bacteria to fungi, viruses and parasites. It may also be caused by non-infectious factors such as cancer, toxic drugs, brain surgery or injuries to the central nervous system (CNS), however, these are not very common. Among the various pathogens capable of causing meningitis, bacterial pathogens are the most common and cause the highest global burden of the disease compared to other pathogen types. Viral meningitis also has some level of prevalence, especially in countries such as the United States, but it presents less severe symptoms than bacterial meningitis. It is commonly caused by a group of viruses called Enteroviruses, along with other viruses such as Herpes Simplex Virus, Mumps Virus, West Nile Virus, etc. Meningitis caused by fungal and parasitic infections are rare, but may be life threatening in some circumstances.
A number of different bacteria capable of invading the central nervous system can actually cause bacterial meningitis. Some of these bacteria include Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae, Listeria monocytogenes, and a number of others. It is the most common and most severe form of meningitis, having fatal consequences if not given adequate medical attention. Viral meningitis tends to be less severe than that caused by bacteria, and tends to have higher prevalence in children. Individuals with a strong immune system usually recover from the viral infection with little or no medical treatment. Fungal meningitis is caused by inhaling fungal spores from the environment, and is most likely to occur in individuals with a weakened immune system like HIV and Cancer patients. Examples of some fungi capable of causing meningitis include Cryptococcus, Coccidioides, Histoplasma and Blastomyces. Parasitic meningitis is much less common than the other forms of meningitis and is only caused by parasites that are capable of infecting the CNS. An example is the parasitic amoeba Naegleria fowleri, which is found in some water sources like ponds and swimming pools, thus, it is more likely to infect swimmers, usually through the nasal route when water enters a person’s nostrils.
What are the Signs and Symptoms of Meningitis?
Meningitis caused by Bacteria and Viruses tends to have similar symptoms at the beginning of infection, but as the disease progresses, the symptoms of bacterial meningitis tend to be more severe than that of viral meningitis. General symptoms include nausea, vomiting, headaches, fever and chills, lethargy and sensitivity to bright light. As the disease progresses, the symptoms get more severe (in bacterial), along with symptoms such as having a stiff neck, seizures, delirium, loss of appetite or thirst, and sometimes, a peculiar skin rash may develop. In infants, some symptoms that may be observed include high fever, excessive sleepiness, constant crying, vomiting and poor feeding, inactivity, stiffness of the body and neck, and bulging of the fontanel (soft spot on the baby’s head).
Bacterial meningitis causes the most severe symptoms and can be fatal within a few days if immediate treatment with the appropriate antibiotics is not commenced. It is important to identify the specific cause of meningitis in an individual, so as to administer the befitting medical treatment. Delayed treatment increases the risk of permanent brain damage or death.
How can Meningitis be diagnosed?
Diagnosis of Meningitis is primarily based on the individual’s health history and symptoms. A lumbar puncture is usually done at the abdominal portion of the patient’s spine, and cerebrospinal fluid is extracted to test for the presence of infectious pathogens in the fluid, which would help to confirm the type of meningitis, and the mode of treatment that would be best. Other additional tests can be carried out, such as blood culture to identify any bacterial species present in the blood, or a White blood cell count (WBC) to determine the proportion of white blood cells present in the blood, as a high number of white blood cells indicates the presence of an infection. A CT Scan of the Brain may also be carried out to detect cerebral abnormalities such as sinusitis or brain abscesses.
How can Meningitis be treated?
Treatment of meningitis depends on the type of infection. Bacterial meningitis requires immediate treatment with intravenous antibiotics (injected into the bloodstream) to ensure circulatory effectiveness. There is no specific antibiotic used, as the type of antibiotic to be used depends on the causative bacteria. Viral meningitis usually resolves on its own with management of symptoms, but advanced cases require treatment with intravenous antiviral drugs. Fungal meningitis is treated with injectable antifungal medications. Treatment of parasitic meningitis may involve treating just the symptoms or treating the actual infection, depending on the severity of the disease.
How best can Meningitis be prevented?
The microorganisms that cause meningitis (especially bacteria and viruses) are quite common in our environment and can be spread through sneezing, coughing, kissing, and sharing eating utensils or items like cups and toothbrushes. Meningitis infections can be prevented by maintaining hygienic practices such as washing hands properly, not sharing personal items with people and covering your mouth when sneezing or coughing. Maintaining a proper diet and getting adequate rest is important in order to ensure a healthy immune system.
The best mode of prevention for meningitis is by vaccination against the causative pathogens. A number of effective vaccines have been approved by the World Health Organization (WHO) and Centers for Disease Control and Prevention (CDC) for protection against certain forms of bacterial meningitis. These vaccines include the Haemophilus influenzae type b (Hib) Vaccine, the Pneumococcal Conjugate Vaccine (PCV13), Pneumococcal Polysaccharide Vaccine (PPSV23) and the Meningococcal Conjugate Vaccine. These vaccines are effective against the major causative pathogens of bacterial meningitis, and have defined doses suitable for administration to both children and adults.
Reference
- World Health Organization. Meningitis. https://www.who.int/health-topics/meningitis
- Centers for Disease Control and Prevention (2020). Meningitis. https://www.cdc.gov/meningitis/index.html
- Mayo Clinic (2020). Meningitis – Symptoms and Causes. https://www.mayoclinic.org/diseases-conditions/meningitis/symptoms-causes/syc-20350508