What is the overview of Nipah virus, its symptoms, treatment, and prevention, particularly for patients who have recently traveled to or have exposure to regions where the virus is common, such as Southeast Asia and Africa?

Nipah Virus: Clinical Overview

What is Nipah Virus?

Nipah virus (NiV) is a highly lethal zoonotic paramyxovirus transmitted from fruit bats to humans, causing severe encephalitis and respiratory disease with mortality rates of 40-75%, requiring immediate isolation and supportive care as no specific antiviral treatment is currently approved. 1, 2, 3

Geographic Distribution and Transmission

• Endemic regions include South and Southeast Asia, particularly Bangladesh, India, Malaysia, Singapore, and the Philippines 1, 2, 4
• Pteropid fruit bats (flying foxes) serve as the natural reservoir 1, 2
• Transmission occurs through three primary routes:
  • Consumption of raw date palm sap or fruit contaminated by infected bat saliva or urine 2, 4, 5
  • Direct contact with infected pigs (Malaysia-Singapore outbreak) or horses (Philippines outbreak) 1, 2, 5
  • Person-to-person transmission occurs in approximately 50% of cases through respiratory droplets or contact with infected body fluids 6, 2

Clinical Presentation

Incubation Period

• Typically 4-14 days after exposure 2, 4

Common Symptoms

• Fever (80% of cases), headache (47%), and myalgia (47%) are the most frequent initial symptoms 3
• Altered mental status, drowsiness, and seizures indicate CNS involvement 1, 2
• Respiratory symptoms including shortness of breath and acute respiratory distress syndrome occur in 44% of cases 3
• Vomiting (42.6%), dizziness, and retro-orbital pain 1, 3

Neurological Manifestations

• Myoclonus, dystonia, areflexia, and hypotonia are characteristic neurological signs 1
• Seizures and altered sensorium are the most common complications (39.2% and 35.7% respectively) 3
• MRI may demonstrate discrete focal lesions throughout the brain, predominantly in subcortical and deep white matter of cerebral hemispheres 1

Laboratory Findings

• Thrombocytopenia, leukopenia, and elevated transaminases may be present 2

Diagnostic Approach

Acute Phase Testing (First 7-10 Days)

• RT-PCR from throat swabs, respiratory specimens, CSF, or urine is the primary diagnostic test in the acute phase 1, 2, 3
• Virus isolation in BSL-4 laboratory facilities 1, 2
• Contact CDC Special Pathogens Branch (1-970-221-6400) for diagnostic assistance 1

Convalescent Phase Testing (After 7-10 Days)

• Serology (IgM and IgG antibodies) from serum and CSF becomes positive during the convalescent phase 1, 2, 4
• Paired acute and convalescent sera collected 10-14 days apart 1

Critical Diagnostic Considerations

• Always perform HSV PCR on CSF to rule out treatable causes of encephalitis 6
• Consider other arboviral encephalitides (Japanese encephalitis, dengue) in travelers from endemic regions 1
• EEG may reveal periodic complexes with 1:1 relationship to myoclonic jerks 1

Treatment and Management

Supportive Care (Primary Treatment)

• No FDA-approved specific antiviral treatment exists; management is entirely supportive 1, 2, 5
• Early intubation and invasive mechanical ventilation are recommended for severe hypoxemia rather than prolonged trials of non-invasive ventilation, which increase mortality and staff exposure risk 6
• Continuous ICU-level monitoring of vital signs, oxygen saturation, neurological status, water-electrolyte balance, and organ function 6
• Monitor for complications including ARDS, septic shock, stress ulcers, and deep vein thrombosis 6

Investigational Antivirals

• Ribavirin has limited evidence for efficacy (C-III recommendation) but may be considered 1, 6, 2
• m102.4 monoclonal antibody and favipiravir show some in vitro activity but lack clinical trial data 2

Seizure Management

• Aggressive anticonvulsant therapy is required for myoclonic seizures and status epilepticus 6
• Continuous EEG monitoring to detect subclinical seizure activity 6

Nutritional Support

• High-protein, high-vitamin, carbohydrate-containing diets for patients tolerating oral intake 6
• Early enteral nutrition for critically ill patients; if not feasible, initiate parenteral nutrition promptly 6

Psychological Support

• Provide mindfulness-based stress reduction techniques to relieve anxiety and panic 6
• Positively encourage patients and address concerns promptly 6

Infection Control Measures

Healthcare Worker Protection

• Airborne precautions with N-95 respirators, gowns, aprons, and face shields are mandatory for all suspected or confirmed cases 6
• Standard precautions and strict hand hygiene 2
• Avoid non-invasive ventilation or high-flow nasal oxygen in uncontrolled settings due to aerosolization risk 6

Patient Isolation

• Infected persons must be isolated immediately to prevent secondary transmission 2, 4
• Implement comprehensive infection prevention and control strategies 2

Prognosis and Outcomes

• Case-fatality ratio ranges from 40-75%, with a systematic review reporting 73.9% mortality 2, 3, 7
• 30-50% of survivors develop long-term neurologic sequelae including seizures, cognitive deficits, motor weakness, and behavioral problems 1
• Some patients experience late relapse or recrudescence months to years after initial infection 4

Prevention Strategies

Primary Prevention

• Avoid consumption of raw date palm sap in endemic areas 2, 4, 5
• Avoid contact with sick pigs or horses in outbreak areas 2, 5
• Prevent bat access to date palm collection sites 4

Outbreak Response

• Rapid case identification and isolation are essential to contain outbreaks 4
• Contact tracing and monitoring of exposed individuals 4
• No licensed vaccine is currently available 2, 7

Critical Pitfalls to Avoid

• Do not delay intubation with prolonged non-invasive ventilation trials—this increases mortality and staff exposure during emergency intubation 6
• Do not discharge patients without comprehensive follow-up plans, as neurological sequelae may emerge later 6
• Do not assume absence of risk based on lack of reported cases, as surveillance systems may be inadequate 4
• Always maintain high clinical suspicion in travelers returning from South/Southeast Asia with fever and encephalitis 1