What is Nipah Virus?
The Nipah virus (NiV) is a type of RNA virus that is part of the Paramyxoviridae family and the Henipavirus group. These groups also include other viruses like the Hendra virus (HeV) and the Cedar virus. NiV was first discovered in Malaysia in 1998 and has caused several outbreaks in South and Southeast Asia since then. The World Health Organization prioritizes NiV because it often causes outbreaks.
NiV is a zoonotic disease, meaning it can be transmitted from animals to humans. The virus is typically carried by fruit bats of the Pteropus species, and it’s believed that the virus was passed from these bats to pigs, and then onto humans. NiV is considered a high-risk virus (Biological Safety Level 4 – BSL 4) because there are currently no effective treatments or vaccines against it. Because it’s a zoonotic disease, a combined approach that includes focusing on human, animal, and environmental health is necessary to prevent any future transfer of the virus from animals to humans.
What Causes Nipah Virus?
The Nipah virus is a type of paramyxovirus, which falls under the subfamily of Paramyxovirinae, the family of Paramyxoviridae, and the order of Mononegavirales. This simply means it belongs to a large group of similar kinds of viruses. NiV, as it’s also known, is a kind of RNA virus, which means it’s made of a single strand of genetic material that’s covered by a protective envelope. It’s typically found in bats known as Pteropus fruit bats, and it can survive for about 18 hours in the urine from these bats.
NiV spreads in a few ways, such as through eating food that’s been contaminated, touching bodily fluids from an infected human or animal, and exposure to droplets or tiny particles in the air. Factors that can increase the chance of getting infected include being in close proximity with someone who’s infected. Contaminated foods can include fruits and date palm sap that’s been contaminated by fluids from a bat.
Risk Factors and Frequency for Nipah Virus
The Nipah virus, or NiV, was first reported near Ipoh city in Perak, Malaysia in 1998. Shortly after, in 1999, the virus was identified in a patient’s spinal fluid in Sungai Nipah village, hence it was named after the village. The same year, an outbreak happened in Singapore, with 11 cases and one death.
In Bangladesh, Nipah virus showed a different pattern, beginning with an outbreak of brain inflammation (encephalitis) in Meherpur in 2001. The notable difference here was that no pigs were involved in this outbreak because pig farming isn’t practiced in Bangladesh, a predominantly Muslim country. Subsequent seasonal outbreaks are believed to be separate instances of the virus spilling over from animals to humans.
- In 2001, an encephalitis outbreak in Siliguri, West Bengal, India, nearby Bangladesh, is now believed to have been an outbreak of Nipah.
- In both Bangladesh and Siliguri, drinking fresh date palm sap is thought to have facilitated the direct spillover of NiV from bats to humans.
- In 2014, the Philippines reported an outbreak where exposure to infected horses was the route of NiV transmission, similar to the Hendra virus infections in Australia.
- In 2018 and 2019, Kerala, a southern state in India, reported two separate NiV outbreaks, with fruit bats suspected in the spillover events.
Signs and Symptoms of Nipah Virus
Nipah virus infection, which incubates anywhere from 4 days to 2 weeks, can present in several ways. Some people might experience brain inflammation (encephalitis) or respiratory issues, while others might not show any symptoms. It’s worth noting that the symptoms can vary depending on the strain of the virus; for instance, about 70% of patients in India and Bangladesh experience respiratory problems, but this isn’t the case for patients in Malaysia.
The illness typically begins with symptoms like fever, headache, dizziness, and vomiting. These symptoms progress quickly into encephalitis, which can cause drowsiness, confusion, and disorientation, and can lead to a coma. Among the symptoms related to the central nervous system, a decreased level of consciousness, dysfunction of the brainstem, muscle twitching, lack of reflexes, weak muscle tone, and signs of cerebellar dysfunction are common. Severe cases of the illness can lead to multiple organ dysfunction, gastrointestinal bleeding, and kidney failure. In Bangladesh outbreaks, 69% of patients experienced difficulty breathing, and some even developed Acute Respiratory Distress Syndrome.
- Fever
- Headache
- Dizziness
- Vomiting
- Drowsiness
- Disorientation
- Confusion
- Coma
In some cases, survivors of Nipah virus encephalitis may continue to experience long-term neurological effects. These may include fatigue, brain disease, uncontrolled eye movement, abnormal neck muscle contraction, weakness in specific areas, and facial paralysis. Furthermore, a small percentage of patients might experience a delayed onset of the illness, or even possible relapses after recovering from the initial infection.
Testing for Nipah Virus
Patients suspected to have Nipah virus infection may often have low levels of white blood cells and platelets. Levels of certain liver enzymes (alanine aminotransferase and aspartate aminotransferase) may also be raised. Analyzing the cerebrospinal fluid (CSF), the fluid that surrounds your brain and spinal cord, usually reveals a high count of white blood cells or protein levels, or both.
In the acute (sudden and severe) stage of Nipah virus infection, antibodies against the virus are found in the blood in over 70% of cases, but in less than a third of CSF samples. The presence of the virus in CSF samples was strongly linked with a higher risk of death.
An EEG scan, which monitors brain activity, can show a specific pattern seen in encephalitis (brain inflammation) characterized by sharp and slow waves occurring every 1 or 2 seconds.
Typical findings on an MRI scan include multiple small lesions (damaged areas) located in the white matter of the brain, areas around the ventricles (chambers of the brain that contain CSF), and the corpus callosum (the part of the brain that connects the two hemispheres). These damage spots do not cause swelling in the brain or pressure effects, and few patients show signs of enhancement (increased visibility) in the leptomeninges (membranes that cover the brain and spinal cord) or the parenchyma (tissue inside the brain).
The Nipah virus can be identified from urine and respiratory secretions using tests called culture and PCR. Real-time RT-PCR is a super sensitive test that can detect even small amounts of the virus better than regular tests.
While blood tests for antibodies against the virus are not very helpful in diagnosing acute (sudden and severe) infections, they can be useful in studying how the disease spreads in a population.
Treatment Options for Nipah Virus
If you have a NiV infection, the doctors will keep you quarantined, which means you’ll be kept away from others, to prevent the virus from spreading. The main treatment involves managing your symptoms and keeping you as comfortable as possible. This is called supportive treatment.
Ribavirin is a type of medication called an antiviral. This drug has been effective against similar viruses, like the one that causes respiratory infections. However, there are mixed reports about its effectiveness against the NiV virus. Some studies indicate it can help reduce death rates, while others found it to have no effect. Even so, ribavirin is recommended for use in Nipah virus infections according to the Indian National Centre for Disease Control.
Other medications, like acyclovir, chloroquine, and ephrin-B2, are being studied to see if they could be potential treatment options. In particular, a drug called favipiravir, which is used to treat the flu in Japan, has proven to be effective in hamsters. Another promising treatment is a human monoclonal antibody, which has shown effectiveness in ferrets and other non-human primates.
Before you can be discharged from the hospital, doctors need to be sure you don’t have the virus anymore. They will do a throat swab and test it using a procedure called RT-PCR. Once tests show you’re no longer carrying the virus, you may still need to stay in isolation for 21 days after the date the infection was confirmed, to ensure it doesn’t spread to others.
What else can Nipah Virus be?
When trying to diagnose a disease that shows symptoms like fever, brain inflammation (encephalitis), or severe lung condition (ARDS), the patient’s travel history, current health incidents, and personal background can help pinpoint the actual illness. This diagnostic process is called differential diagnosis. In the case of Nipah virus (NiV) infection, similar symptoms could be caused by the following diseases:
- Japanese encephalitis
- Measles
- Rabies
- Dengue encephalitis
- Cerebral malaria
- Scrub typhus
- Leptospirosis
- Herpes encephalitis
- Bacterial meningitis
What to expect with Nipah Virus
The death rate for certain medical conditions can vary greatly, ranging from 40% to 100%. Factors that can make the prognosis worse include being older in age and having severe involvement of the brain stem. The outcome and death rates can also depend on the type of virus causing the condition. For example, the Malaysian variant of certain viruses has shown to have lower death rates.
Possible Complications When Diagnosed with Nipah Virus
Even if someone survives, there could be lasting effects on their brain and nerves, including changes in behavior, abnormal neck movements, trouble moving their eyes, weakness, and paralysis on one side of the face. A small percentage of patients may experience a return of this brain infection after they’ve initially recovered.
- Changes in behavior
- Abnormal neck movements
- Difficulty moving eyes
- Muscle weakness
- Paralysis on one side of the face
- Return of brain infection after initial recovery
Preventing Nipah Virus
Educating patients is vital in preventing the disease, especially as there’s no effective treatment currently available. This education should concentrate on how to avoid eating or coming into contact with date palm sap, which can cause infection. The World Health Organization (WHO) also advises people to steer clear of bats and pigs, and not to eat fruit that bats have bitten or raw date palm sap.
People who work in animal slaughter are encouraged to wear protective clothing. In the event of an outbreak, spread of the disease from person to person can be limited by reducing contact and using personal protective equipment, which include items such as masks and gloves to create a barrier against infections.
Another crucial part of managing an outbreak involves ‘contact tracing’ and ‘quarantine’. Contact tracing is the process of identifying and monitoring individuals who may have been exposed to the disease. Quarantining means isolating these individuals to prevent them from spreading the disease to others. These steps play an important role in preventing the further spread of the disease during an outbreak.
