What are the signs and symptoms of Nipah virus infection?

Nipah Virus Infection: Signs and Symptoms

Initial Clinical Presentation

Nipah virus infection typically begins with nonspecific symptoms after an incubation period of 4 days to 2 weeks, with fever being the most common presenting feature, occurring in 80% of cases. 1, 2, 3

Early Symptoms (First Few Days)

• Fever is the predominant initial symptom, present in 80% of patients 2
• Headache occurs in 47% of cases 2, 3
• Myalgia (muscle pain) affects 47% of patients 2, 3
• Vomiting is reported in 42.6% of cases 2, 3
• Dizziness is a common early complaint 3

Neurological Manifestations

The hallmark of severe Nipah virus infection is acute encephalitis with altered mental status, which develops over the next few days following initial symptoms. 1, 2

Central Nervous System Features

• Altered sensorium (mental status changes) occurs in 44.1% of patients and represents a critical progression marker 2
• Seizures are a common complication, affecting 39.2% of cases 2
• Segmental myoclonus is a characteristic neurological finding 3
• Areflexia and hypotonia are distinctive physical examination findings 1, 3
• Abnormal pupillary reflexes may be present 3

Movement Disorders

• Dystonia can develop as the disease progresses 1
• Choreoathetoid movements may occur 3

Respiratory Manifestations

Respiratory involvement is a major feature of Nipah virus infection, particularly in Bangladesh and India outbreaks, occurring in 44.1% of cases. 2, 4

• Shortness of breath progressing to acute respiratory distress syndrome (ARDS) affects 44.1% of patients 2
• Respiratory disease can be the primary clinical syndrome rather than encephalitis 4

Cardiovascular Findings

• Tachycardia is frequently observed 3
• Hypertension may develop during the course of illness 3

Disease Severity and Progression

The clinical presentation ranges from asymptomatic infection to fatal encephalitis, with a mortality rate of 73.9% in documented cases. 2, 3, 4

Critical Complications

• Altered sensorium as a complication occurs in 35.7% of cases 2
• Seizures represent the most common complication at 39.2% 2
• Progression from initial symptoms to severe encephalitis or respiratory failure can occur rapidly 2

Key Clinical Distinctions

Unlike many viral encephalitides, Nipah virus characteristically presents with a combination of encephalitis AND respiratory symptoms, along with distinctive movement disorders including myoclonus and areflexia. 1, 2, 3

• The presence of segmental myoclonus with areflexia and hypotonia should raise strong suspicion for Nipah virus in endemic areas 1, 3
• Fever with altered mental status developing 4-14 days after potential bat or pig exposure in South Asia should prompt immediate consideration of Nipah virus 3, 4

Geographic and Epidemiologic Context

• Symptoms should be interpreted in context of exposure history to fruit bats, contaminated date palm sap, infected animals (particularly pigs), or close contact with infected patients 4, 5
• Person-to-person transmission occurs in approximately 50% of recognized cases in Bangladesh, making exposure to infected patients' saliva a critical risk factor 5

Clinical Pitfalls to Avoid

• Do not dismiss the diagnosis based on absence of animal exposure, as human-to-human transmission accounts for half of cases in recent outbreaks 5
• Do not wait for the full constellation of symptoms before considering Nipah virus, as early recognition is crucial given the 73.9% mortality rate 2
• Do not overlook respiratory symptoms as the sole manifestation, as some patients present primarily with respiratory disease rather than encephalitis 4