Bacterial and Viral Meningitis
Description of the Disease
Meningitis is an inflammation of the membranes (meninges) surrounding the brain and spinal cord. It typically presents with severe headache, fever, nausea, and vomiting and is one of the most serious infections of the central nervous system. Before the introduction of antibiotics, bacterial meningitis was almost always fatal. Despite modern treatment, it is still associated with significant mortality and long-term complications. Approximately 5–40% of patients die, while 10–60% of survivors may experience permanent neurological deficits.
The most common cause of bacterial meningitis is Neisseria meningitidis, which has several serogroups, including A, B, C, W, X, and Y. Other bacterial causes include Streptococcus pneumoniae, Haemophilus influenzae, Leptospira species, and Mycobacterium tuberculosis. Viral meningitis is most commonly caused by enteroviruses and herpes viruses.
Neisseria meningitidis is found worldwide and is highly sensitive to environmental conditions. People of all ages can become infected, although infants, young children, and older adults are at the highest risk of severe disease. Approximately 2–5% of healthy individuals carry the bacteria without developing symptoms. The primary source of infection is an infected person with an upper respiratory tract infection or an asymptomatic carrier. Transmission occurs through respiratory droplets released during coughing, sneezing, or talking. Most infected individuals develop only a mild upper respiratory tract infection, while meningitis develops in a small proportion of cases, depending largely on the individual’s immune response. The incidence of meningitis is highest during the winter and spring months.
Symptoms
Symptoms include a high fever (above 38°C), severe headache, nausea, vomiting, irritability, and neck stiffness. Neurological signs may include facial weakness, inability to wrinkle the forehead, and, in some cases, a slow heart rate (bradycardia). Other characteristic findings include opisthotonus and a skin rash that may range from small petechiae to large purpuric lesions. The rash may be subtle and easily overlooked.
Diagnosis
Diagnosis is based on the patient’s clinical presentation together with laboratory investigations. Blood tests, cerebrospinal fluid (CSF) analysis, CSF microscopy and culture, and throat cultures are performed to identify the causative organism. The most important diagnostic test is lumbar puncture with cerebrospinal fluid analysis, which typically demonstrates elevated CSF pressure and characteristic inflammatory changes.
Treatment
Bacterial meningitis requires immediate antibiotic therapy. Penicillin is commonly used when appropriate, while cefuroxime, ceftriaxone, or chloramphenicol may be used as alternatives depending on the causative organism and clinical circumstances. Additional treatment may include glucocorticoids, diuretics such as furosemide or mannitol to reduce intracranial pressure, intravenous fluids, and anticonvulsants when necessary.
Viral meningitis is treated with supportive care, and antiviral medications may be prescribed when indicated, depending on the causative virus. Antibiotics are not effective against viral infections.
Vaccination is an important preventive measure. Vaccines against several Neisseria meningitidis serogroups, including serogroup B, are available and help reduce the risk of meningococcal disease. Rifampicin prophylaxis is recommended for close contacts who are carriers or have been exposed to meningococcal infection.
Source | Author Doctor Nikas Samuolis, reviewed by Prof. Virginijus Šapoka | Vilnius University | Faculty of Medicine | Head of the Department of Internal Medicine, Family Medicine, and Oncology