Difference Between Viral and Bacterial Meningitis

Meningitis is inflammation of the meninges caused by bacteria, viruses, fungi or parasites. Both bacterial and viral meningitis present the same. The clinical history, examination finding, methods of investigation and treatment protocols are the same. However, investigation findings, specific treatment and prognosis are different. It is important to make a correct diagnosis as to whether it is viral or bacterial meningitis because viral meningitis is self-limiting and has no long term sequelae while bacterial meningitis is more severe and if meningitis is suspected, treatment should be started without delay. This article will talk about meningitis in detail, highlighting their clinical features, symptoms, causes, investigation and diagnosis, prognosis, treatment, and the differences between bacterial and viral meningitis.

Meningitis is a killer, and it kills quickly. Organisms like E coli, beta hemolytic streptococci, Listeria moncytogenes, Heamophilus, Nisseria meningitidis, pneumococcus cause meningitis. Meningitis presents with headache that worsens when exposed to light, stiff neck, Kernig’s sign (pain and resistance on passive knee extension with hips fully flexed), Brudzinski sign (hips flex on bending head forward) and opisthotonus. These are known as meningeal features. Meningitis increases pressure inside the skull. This is characterized by headache, irritability, drowsiness, vomiting, fits, papilledema, reduced level of consciousness, irregular respiration, low pulse rate, and high blood pressure (Read the Difference Between Pulse Rate and Blood Pressure). When the organism enters the bloodstream septic signs like feeling ill, joint swelling, joint pain, odd behavior, rash, diffuse intravascular coagulation, rapid breathing, rapid pulse, and low blood pressure occur.

Treatment for meningitis should not be delayed until test results arrive. If meningitis is suspected, nothing should delay intravenous antibiotics. Airway, breathing, and circulation should be maintained. High flow oxygen therapy via a face mask is good. Treatment protocol differs according to the presentation. If septic signs predominate, lumbar puncture should not be attempted. If the patient is in shock, volume resuscitation is indicated. If meningitic features predominate at presentation, lumbar puncture should be attempted if no features of increased intracranial pressure are present. Intravenous antibiotics should be given. If there is any indication of respiratory failure, intubation should not be delayed.

Complications of meningitis are cerebral edema, cranial nerve lesions, deafness, and cerebral venous sinus thrombosis. Lumbar puncture is critical to diagnosis. If there are no features of increased intra cranial pressure, the lumbar puncture should be done. If there are features of increased pressure inside the skull, CT should precede lumbar puncture. 3 bottles of cerebrospinal fluid should be sent for gram stain, Zheil neilson stain, cytology, virology, glucose, protein and culture. Cerbrospinal fluid analysis may be normal at an early stage.  If indicated lumbar puncture should be repeated. Other tests like blood culture, blood glucose, full blood count, urea, electrolytes, chest x-ray, urine culture, nasal swab and stools for virology may be indicated.

Risk factors for meningitis are overcrowding, head injury, infective focus, very young, very old, complement deficiency, antibody deficiency, cancers, sickle cell disease, and CSF shunts. Acute bacterial meningitis has  mortality of 70 to 100% untreated; Neisseria meningitides has an overall mortality of 15% in the west. Survivors are at risk of permanent neurological deficits, mental retardation, sensorineural deafness and cranial nerve palsies.

What is the difference between Bacterial and Viral Meningitis?

• Bacterial meningitis has a poor prognosis while viral meningitis is self –limiting, has a good prognosis and no long term sequelae.

• Upon lumbar puncture, CSF looks turbid in bacterial meningitis while it looks clear in viral meningitis.

• Mononuclear cells predominate in viral meningitis while polymorphs predominate in bacterial meningitis.

• White cell count in CSF is less than 1000 in viral meningitis while it’s more than 1000 in bacterial meningitis.

• CSF glucose concentration is less than half of that of plasma in bacterial meningitis while, in viral meningitis, CSF sugar concentration is more than half of that of plasma.

• CSF protein concentration is more than 1.5g/L in bacterial meningitis while it is less than 1g/L in viral meningitis.

• There are organisms visible in smear or culture, in bacterial meningitis while no organisms are seen in viral meningitis.


Read also the Difference Between Meningitis and Meningococcal