What are the signs and symptoms of Nipah virus infection in adults, particularly older adults with underlying medical conditions?

Signs and Symptoms of Nipah Virus Infection in Adults

Nipah virus infection presents most commonly with fever, followed by neurological manifestations including altered mental status and respiratory distress, with a mortality rate exceeding 70% in documented cases. 1

Initial Presenting Symptoms

The early clinical presentation is typically nonspecific and includes:

• Fever occurs in approximately 80% of cases and is the most common initial symptom 1
• Myalgia (muscle pain) affects 47% of patients 1
• Headache is present in 47% of cases 1
• Vomiting occurs in 42.6% of patients 1

These initial symptoms typically develop 5-14 days after exposure, though the incubation period can range from 4 days to 2 weeks. 2, 3

Neurological Manifestations

Nipah virus characteristically causes severe encephalitis with distinctive neurological features:

• Altered sensorium (depressed consciousness) develops in 44.1% of cases and represents a critical warning sign 1
• Seizures are a common complication, occurring in 39.2% of patients 1
• Myoclonic jerks may occur, though less commonly than in other viral encephalitides 4
• Focal neurological deficits including weakness, cranial nerve palsies, and movement disorders can develop 5
• Progressive encephalitis with deteriorating mental status is characteristic of severe disease 3, 5

The neurological deterioration can be rapid, with patients progressing from mild confusion to coma within days. 4

Respiratory Manifestations

Respiratory involvement is a prominent feature, particularly in older adults with underlying conditions:

• Shortness of breath and acute respiratory distress syndrome (ARDS) occur in 44.1% of cases 1
• Severe respiratory distress requiring mechanical ventilation develops in a substantial proportion of patients 4
• Respiratory failure is a major cause of mortality and can develop rapidly 3

The respiratory syndrome may occur concurrently with or independently of neurological symptoms. 5

Clinical Course and Complications

The disease progression follows a characteristic pattern:

• Rapid deterioration is common, with patients requiring ICU-level care within days of symptom onset 4
• Altered consciousness persisting or worsening despite supportive care indicates severe disease 1
• Seizures and status epilepticus require aggressive anticonvulsant therapy 4
• Vasculitis and thrombotic complications can occur, manifesting as stroke-like episodes or multifocal brain lesions 6

Neuroimaging Findings

Brain MRI abnormalities are present in the majority of symptomatic cases:

• Small infarcts and areas of cytotoxic edema are common findings 6
• Vasogenic edema may develop in more severe cases 6
• Multifocal lesions can appear throughout the brain, including white matter involvement 6
• Inflammatory changes with perivascular infiltrates may be visible 6

These imaging findings help distinguish Nipah virus encephalitis from other causes of acute encephalitis. 6

High-Risk Features in Older Adults

Older adults with underlying medical conditions face particularly high risk:

• Pre-existing cardiovascular disease may worsen outcomes due to the vasculitic component of Nipah infection 6
• Diabetes and hypertension are common comorbidities that complicate management 1
• Immunocompromised states may lead to more severe or atypical presentations 3
• Rapid progression to respiratory failure is more common in older patients with underlying lung disease 4

Critical Warning Signs Requiring Immediate Escalation

The following features indicate imminent treatment failure and require immediate consideration of intubation rather than prolonged trials of non-invasive support: 4

• Persistent or worsening altered consciousness despite initial resuscitation
• Respiratory rate persistently >25 breaths per minute
• Rapid desaturation when disconnected from oxygen support
• New onset confusion or severe agitation
• Signs of impending respiratory arrest

Do not delay intubation by attempting prolonged trials of non-invasive ventilation or high-flow nasal oxygen, as this increases mortality and puts healthcare workers at risk during emergency intubation. 4

Mortality and Prognosis

The overall mortality rate for Nipah virus infection is 73.9% in documented case series, making it one of the most lethal emerging viral infections. 1 Death typically results from progressive encephalitis, respiratory failure, or cardiovascular collapse. 3, 5

Human-to-human transmission occurs in approximately 50% of cases, primarily through contact with infected patients' respiratory secretions or saliva, necessitating strict airborne precautions with N-95 respirators for all healthcare workers. 4, 2