Viral Meningitis

Meningitis

Aseptic meningitis is a general term that indicates non-pyogenic cellular responses induced by agents of different etiologies. Patients usually show acute meningeal symptoms, fever, CSF pleocytosis dominated by lymphocytes. After several laboratory tests, obtained the causes of aseptic meningitis is mostly derived from the virus, including enterovirus and Herpes Simplex Virus (HSV).

Viral meningitis is an inflammation of leptomeningen as a manifestation of CNS infection. The term viral is used because it is the causative agent, and the use of the term "meningitis", imply no involvement of the parenchyma of the brain and spinal cord. However, pathogenic virus can cause infection is a combination of meningoencephalitis or meningomielitis.

       In viral meningitis, the clinical course is usually limited, with complete recovery in 7-10 days. More than 85% of cases are caused by non-polio enteroviruses; hence, disease characteristics, clinical manifestations, and epidemiology suggests enteroviral infection. Measles, polio, and lymphocytic choriomeningitis virus (LCMV) is now a threat to developing countries. Polio remains a major cause of myelitis in some areas of the world.


Epidemiology
       In the United States, more than 10,000 cases are reported each year, but the true incidence may reach up to 75,000. Lack of reporting because no clinical outcomes most cases and the inability of some viral agents to grow in culture. According to the CDC report, patient care in hospital from viral meningitis varies from 25.000 to 50.0000 per year. In some reports estimated incidence of 11 per 100,000 population per year.

        Distribution of the clinical incidence of viral meningitis in the world varies. The cause of viral meningitis in the world including enterovirus, measles virus, VZV, and HIV. Symptoms of meningitis may occur slightly at 1 of 3000 cases of infection by these agents. Finnish study estimated the incidence of 19 per 100,000 population in children aged 1-4 years. This is a significant contrast to 219 cases per 100,000 were estimated for children younger than 1 year. Japaneese B encephalitis virus, the most common pathogens of viral meningitis in the world, causing more than 35,000 infections annually through Asia but is estimated to cause 200-300 times the sum of subclinical infection. Distribution and characteristics of the attack by arthropod vectors, showed strong geographic variability. The lack of effective vaccination rules in third world countries play a role in the geographic inequality of other infectious agents.

Risk factors 

         Beyond the neonatal period, the mortality rate associated with viral meningitis is less than 1%; morbidity rate is also low. Physicians should be aware of viruses that can cause meningitis can also cause more serious infections in the CNS as well as other organs. The statistical report of the World Health Organization (WHO) 1997 report of enteroviral meningitis with sepsis is the most common cause of all 5 of mortality in neonates. Complications such as brain edema, hydrocephalus, and seizures may occur in the acute period.

• Race
There is no specific racial predilection has been identified

• Sex
Depending on the viral pathogen, which affects the ratio of women and men can vary. Enterovirus is thought to affect male 1.3-1.5 times more often than women. Most arboviruses have diverse characteristics of the attack, affects both genders but at the age of sharing.

• Age
o The incidence of viral meningitis decreases with age
o Neonates are at greatest risk and will have a significant risk of morbidity and mortality.
o Some arboviruses very extreme attack at some age, with older people who are at greatest risk for infection, while the peak of measles and smallpox arise in late adolescence.

Etiology
• Enteroviruses cause more than 85% of all cases of viral meningitis. They are a family of Picornaviridae ("pico" for small, "rna" for ribonucleic acid), and including echovirus, coxsackie virus A and B, poliovirus, and a number of enteroviruses. 

• Arboviruses cause only 5% of cases in North America

• Smallpox: a family of paramyxovirus, measles virus is the first agent of meningitis and meningoencephalitis.

• Herpes family viruses: HSV-1, HSV-2, VZV, EBV, CMV, and human herpes virus  collectively causes about 4% of cases of viral meningitis, with HSV-2 became the highest attacker.

• Lymphocytic choriomeningitis virus: entry into the family of arenaviruses LCMV. When this is rarely the cause of meningitis, the virus is transmitted to humans through contact with rodents or their excretions. They are at high risk to laboratory workers, pet owners, or people who live in non-hygienic areas.

• Adenovirus: Adenoviruses an uncommon cause of meningitis in individuals immunocompeten but it is a major cause of AIDS patients, infection can occur simultaneously with upper respiratory tract infections.

• Measles: Morbili virus, is the cause of the most common today. Characteristic maculopapular rash assist in diagnosis. Most cases occur in young people in school and college. Measles remains a global health threat with the highest attack rate of existing infections; eradication of measles is an important public health goal of WHO.

• Clinicians should consider the possibility of partial bacterial meningitis as the etiology, for aseptic disease patients; for example, patients with bacterial otitis and sinusitis who have been using antibiotics, may present with meningitis, and CSF were identical to the discovery of viral meningitis.



Source:
1. Pict: http://www.humanillnesses.com/Infectious-Diseases-He-My/Meningitis.html