Central Nervous System Infections

Causes & Risk Factors

Central nervous system infections can be caused by bacteria, viruses, or fungi, with risk influenced by several factors:

•  Bacterial, viral, or fungal pathogens — different organisms cause meningitis or encephalitis with different urgency and treatment implications.

•  Recent neurosurgery or head trauma — creates a route for infection to reach the central nervous system.

•  Weakened immune system — significantly increases risk and broadens the range of possible causative organisms, including unusual or opportunistic pathogens.

•  Close contact with a person diagnosed with bacterial meningitis — certain bacterial causes can spread between close contacts.

•  Incomplete vaccination status — relevant to certain vaccine-preventable causes of bacterial meningitis.

Symptoms & When to Test

Central nervous system infection symptoms can progress rapidly and represent a medical emergency requiring immediate evaluation.

•  Severe headache, often described as the worst the person has experienced

•  Neck stiffness

•  High fever

•  Sensitivity to light (photophobia)

•  Altered consciousness, confusion, or difficulty waking

•  Seizures

•  In infants — bulging soft spot, high-pitched crying, or poor feeding, alongside other signs

When Should You Consider Testing?

Severe headache with neck stiffness, fever, photophobia, or altered consciousness is a medical emergency requiring immediate evaluation — this is not a situation for scheduled or delayed testing. Seek emergency care immediately if these symptoms occur.

Why Tests Are Combined

Because bacterial and viral causes of central nervous system infection can present similarly but require very different, time-critical treatment approaches (bacterial meningitis requires immediate antibiotics, while most viral causes are managed differently), CSF examination combines multiple analyses — cell counts, protein and glucose levels, microscopy, bacterial culture, and viral PCR — to help distinguish between possible causes as quickly as possible.

CSF microscopy and bacterial culture, together with basic CSF chemistry (protein, glucose), provide rapid clues even before culture results are finalized, helping guide immediate empiric treatment decisions while more definitive results are pending.

Additional pathogen-specific molecular tests may be added based on the specific clinical picture — for example, if a specific viral or fungal cause is suspected based on the patient's history, immune status, or geographic exposure — since testing every possible organism for every patient is neither practical nor necessary.

Tests Available at NPL

Most infectious-disease molecular tests and microbiological investigations do not require fasting. However, some blood tests ordered at the same time may have specific preparation requirements. Please follow the instructions provided by your doctor or NPL.

Home Sample Collection

Suspected central nervous system infection is a medical emergency requiring immediate hospital evaluation — this is not appropriate for home sample collection or routine outpatient scheduling.

CSF sample collection requires a lumbar puncture, a specialist procedure performed by a trained doctor in a hospital or clinical setting, and cannot be performed at home under any circumstances.

If you or someone with you has severe headache with neck stiffness, fever, photophobia, or altered consciousness, seek emergency care immediately rather than arranging any laboratory test independently.

NPL supports urgent processing of CSF samples in coordination with the treating hospital once the sample has been obtained by the hospital's medical team.

When to See a Doctor

•  Severe headache with neck stiffness and fever — seek emergency care immediately

•  Sensitivity to light with headache and fever — seek emergency care immediately

•  Confusion, altered consciousness, or seizures with fever — seek emergency care immediately

•  In infants — bulging soft spot, high-pitched crying, or poor feeding with fever — seek emergency care immediately