Nipah virus disease: A rare and intractable disease
Nipah virus (NiV) is a zoonotic virus that is initially transmitted from animals to humans. It is a member of the family Paramyxoviridae and genus Henipavirus. The animal reservoir in nature for NiV are fruit bats (genus Pteropus), which are also known as flying foxes. The virus was first discovered in 1999 following a nipah virus outbreak in domestic pigs and humans in Malaysia and Singapore, resulting in nearly 300 human cases and more than 100 deaths.
How is the Nipah virus transmitted?
According to the World Health Organization, Nipah virus is typically transmitted from infected animals to humans through a variety of mechanisms. Infected fruit bats can spread NiV to domestic animals (e.g., dogs, pigs, cats, goats, and horses) directly or indirectly, through food products contaminated by fruit bats (e.g., raw date palms and date palm sap). Nipah virus infection can occur in humans after close contact with an infected animal; contact with an infected animal’s body fluids, such as saliva, feces, and urine; and through contaminated food products.
Infected humans can then spread NiV to other humans, either through direct human-to-human contact involving exchange of body fluids, such as respiratory droplets, urine or blood; or indirectly through ingestion of contaminated foods. Person-to-person spread of NiV is most common within families, amongst caregivers of NiV infected individuals, and in healthcare settings.
While there have been no other NiV outbreaks in Malaysia and Singapore since 1999, annual outbreaks have been recorded in some parts of Asia, including Bangladesh and India, according to the Centers for Disease Control and Prevention (CDC).
What signs and symptoms does the Nipah virus cause?
Signs and symptoms of Nipah virus infection can range from being asymptomatic to exhibiting mild or severe symptoms of respiratory infection. Signs and symptoms typically appear 4-14 days after exposure to NiV and are usually non-specific. The most common signs and symptoms of NiV often consist of fever, headache, vomiting, muscle pain, cough, sore throat, and difficulty breathing. A phase of acute encephalitis, or brain swelling, may subsequently follow these non-specific symptoms. Acute encephalitis is typically characterized by dizziness; drowsiness; seizures; and altered level of consciousness, which may rapidly progress into a coma within 24-48 hours.
A majority of individuals who survive the acute encephalitis stage make a full recovery; however, death from NiV occurs in an estimated 40-75% of cases. In survivors of acute encephalitis, residual neurological consequences, such as seizure disorders and personality changes, may be observed in 20% of individuals. Some individuals may also relapse or develop delayed onset disease (e.g., experience symptoms months to years after exposure to NiV), which is known as a dormant or latent infection.
How is Nipah virus diagnosed?
Nipah virus infection is typically diagnosed by a medical professional upon a thorough review of symptoms and medical history, and conduction of a physical examination. Since the early signs and symptoms of NiV are generally non-specific, early detection and diagnosis of NiV infection can be challenging. This can therefore hinder survival chances and create challenges in controlling transmission and outbreak. NiV is commonly suspected in those who have been exposed to geographic areas where NiV is common, particularly in individuals with a known exposure.
NiV can be diagnosed during acute illness or after recovery. During the early stages of NiV infection, detection of the virus can be made through real time polymerase chain reaction (RT-PCR) using throat and nasal swabs, cerebrospinal fluid samples, urine samples, and/or blood samples. In the later stages of NiV infection and after recovery, an enzyme-linked immunosorbent assay (i.e., ELISA) may be conducted to detect antibodies, antigens, and proteins specific to NiV and confirm prior NiV infection. The quality, quantity, type, timing of sample collection, and the time needed to transfer samples to the laboratory may all affect the accuracy of laboratory results.
In cases where acute encephalitis is suspected, a lumbar puncture may be conducted to obtain cerebrospinal fluid sample(s) and screen for NiV infection. Imaging of the brain through a CT scan or MRI may also be conducted to assist in the diagnosis of acute encephalitis.
How is Nipah virus treated?
Treatment of NiV is limited to supportive care through rest, hydration, and treatment of specific symptoms as they occur. Supportive medications include acetaminophen and/or ibuprofen to relieve pain and fevers; dimenhydrinate and/or ondansetron to control nausea and vomiting; and dextromethorphan, dexamethasone, ipratropium, or salbutamol inhalers or nebulizers to improve respiratory symptoms. Anti-seizure medications; such as benzodiazepines, levetiracetam, and/or phenytoin; may be used to alleviate seizures associated with acute encephalitis and maintain control of neurological symptoms.
While there are not currently any approved drug treatments for NiV infection, immunotherapeutic treatments known as monoclonal antibody therapies are currently under development and evaluation for treatment of NiV infection. Monoclonal antibody m102.4 is undergoing clinical trials and is being used on a case-by-case basis. Antiviral therapies, such as remdesivir, have shown to be effective in studies on non-human primates after NiV exposure. The drug ribavirin was also used to treat a small number of patients in the initial NiV outbreak; however, the efficacy of this drug in humans remains unclear.
How do you prevent Nipah virus?
Nipah virus infection may be prevented through a variety of infection control measures. In areas where NiV is common, it is recommended that individuals practice regular hand hygiene, avoid close contact with domestic animals and other individuals at high risk of NiV exposure, and avoid areas that fruit bats are known to occupy. It is also recommended for individuals to follow appropriate food hygiene, which includes avoiding food or drink products at high risk of contamination by fruit bats, such as raw date palm sap, raw fruits, or fruit found on the ground. All consumed food items should be thoroughly washed, peeled, and/or cooked; and food products with signs of animal bites should be discarded.
Strict adherence to infection control practices through disinfection and use of personal protective equipment, such as gloves and face masks, on animal premises and in hospitals at high risk of NiV exposure may effectively prevent NiV transmission. In areas where a Nipah virus outbreak is suspected, quarantine should be immediately enacted to restrict contact between infected and non-infected organisms. Such precautions should be prioritized in areas where fruit bats are found, such as Cambodia, Indonesia, Madagascar, the Philippines, and Thailand.
Additional and ongoing preventive measures include raising awareness and continuing research on the Nipah virus and its transmission; increasing surveillance of domestic animals, fruit bats, and people in areas where NiV is known to exist; evaluating new methods to minimize NiV transmission between species; and developing new tools to detect early NiV infection in humans and animals.
What are the most important facts to know about the Nipah virus?
Nipah virus (NiV) is a zoonotic virus that is initially transmitted from animals to humans. The animal reservoir in nature for NiV are infected fruit bats. Nipah virus infection can occur in humans after close contact with an infected animal or its body fluids and through contaminated food products. Infected humans can then spread NiV to other humans, either through direct human-to-human contact or indirectly through ingestion of contaminated foods. The most common signs and symptoms of NiV typically consist of fever, headache, vomiting, muscle pain, cough, sore throat, and difficulty breathing. In severe cases, a phase of acute encephalitis may follow, which may be accompanied by long term residual neurological consequences.
NiV can be diagnosed using a RT-PCR test using throat and nasal swabs, cerebrospinal fluid samples, urine samples, and/or blood samples. In the later stages of NiV infection and after recovery, an ELISA test may be conducted to confirm prior NiV infection. Treatment of NiV is limited to supportive care, which includes rest, hydration, and treatment of specific symptoms as they occur. Nipah virus infection may be prevented through a variety of infection control measures and by raising awareness.
