Introduction to the Nipah Virus
Nipah virus infection in humans results in a variety of clinical signs, ranging from asymptomatic infection (subclinical) to severe respiratory infection and deadly encephalitis.
The case mortality rate is estimated to be between 40% and 75%. This rate varies with the outbreak, depending on local epidemiological surveillance and clinical management skills.
It can be spread to humans through animals (such as bats or pigs), contaminated foods, or directly from person to person.
Nipah virus’s natural host is fruit bats from the Pteropodidae family.
There is right now no treatment or vaccine available for humans or animals. Humans are treated primarily with supportive care.
The 2018 annual review of the WHO R&D Blueprint list of prime concern diseases shows that the Nipah virus requires urgent study and development.
Clinical Symptoms of Nipah Virus Infection
Nipah virus (NiV) is a zoonotic virus (transmitted from animals to humans). It can likely be spread through contaminated food or between people. Infected patients develop a variety of symptoms, including asymptomatic (subclinical) infection, severe respiratory sickness, and deadly encephalitis. The virus can also cause serious disease in animals like pigs, resulting in substantial economic losses for farmers.
Although there have only been a few reported outbreaks in Asia, the Nipah virus infects a wide range of animals and causes serious sickness and death in humans, making it a public health concern.
Outbreak History and Geographic Spread
The Nipah virus was discovered in 1999 during an outbreak among pig breeders in Malaysia. There have been no new outbreaks recorded in Malaysia since 1999. It was also detected in Bangladesh in 2001, and outbreaks have occurred almost every year since then. The disease has also been detected regularly in eastern India. Other regions may be in danger of infection, as evidence of the virus has been discovered in the recognized natural reservoir (Pteropus bat species) as well as numerous other bat species in a number of countries, including Cambodia, Ghana, Indonesia, Madagascar, the Philippines, and Thailand.
During Malaysia’s first documented outbreak, which also affected Singapore, the majority of human infections were caused by direct contact with sick pigs or contaminated tissues. Transmission is suspected to have occurred by unprotected exposure to pig fluids or contact with diseased animal tissue. In following epidemics in Bangladesh and India, the most common cause of infection was the eating of fruits or fruit products (such as raw date palm juice) contaminated with infected fruit bat urine or saliva.
There is currently no research on viral persistence in human fluids or the environment, including fruits.
Nipah virus transmission has also been put on record among family members and carers of affected patients.
During later outbreaks in Bangladesh and India, the Nipah virus moved directly from person to person via close contact with secretions and excretions. In Siliguri, India, in 2001, the virus was also transmitted in a healthcare setting, with 75% of cases involving hospital staff or visitors. From 2001 to 2008, over half of all recorded cases in Bangladesh were caused by human-to-human transmission while giving treatment to sick patients.
Signs and symptoms
Human infections can range from asymptomatic to acute respiratory infections (mild or severe), as well as deadly encephalitis.
In the early stages, infected persons experience symptoms such as fever, headaches, myalgia (muscle pain), vomiting, and a sore throat. This can be followed by dizziness, drowsiness, altered consciousness, and neurological symptoms indicating acute encephalitis. A few people may also develop atypical pneumonia and serious respiratory difficulties, like acute respiratory distress. Seizures and encephalitis are common in severe cases, which can lead to coma within 24-48 hours.
The incubation period (the time it takes for symptoms to appear) is thought to be between 4 and 14 days. However, incubation periods of up to 45 days have been documented.
The majority of persons who survive acute encephalitis recover completely, but some survivors develop long-term neurologic disorders. Approximately 20% of individuals experience persistent neurological effects such as seizure disorder and personality abnormalities. A tiny percentage of patients who recover later have a relapse or delayed onset encephalitis.
The case mortality rate is estimated to be between 40% and 75%. This rate varies with the outbreak, depending on local epidemiological surveillance and clinical management skills.
The basic signs and symptoms of Nipah virus infection are unclear, and the diagnosis is frequently not suspected at presentation. This can deter correct diagnosis and provide difficulties in outbreak identification, efficient and timely infection control measures, and outbreak response activities.
Furthermore, the quality, number, type, and timing of clinical sample collection, as well as the time required to transmit samples to the laboratory, can all have an impact on the accuracy of laboratory results.
Diagnosis and Detection of Nipah Virus
Nipah virus infection can be diagnosed based on clinical history during the acute and convalescent stages of the disease. The primary tests performed are real-time polymerase chain reaction (RT-PCR) from bodily fluids and antibody detection using enzyme-linked immunosorbent assay (ELISA). Else tests done consist of the polymerase chain reaction (PCR) assay and virus isolation using cell culture.
Treatment and Prevention Strategies
There are presently no treatments or vaccines available for Nipah virus infection, even though WHO has specified Nipah as a priority disease in the WHO Research and Development Blueprint. Intensive supportive care is recommended for severe respiratory and neurologic problems.
Nipah virus’s natural hosts are fruit bats of the Pteropodidae family, notably those from the Pteropus genus. Fruit bats appear to be disease-free. It is assumed that the geographical distribution of Henipaviruses overlaps with that of the Pteropus group.
This idea was supported by evidence of Henipavirus infection in Pteropus bats from Australia, Bangladesh, Cambodia, China, India, Indonesia, Madagascar, Malaysia, Papua New Guinea, Thailand, and Timor-Leste. African fruit bats of the genus Eidolon, family Pteropodidae, tested positive for antibodies to Nipah and Hendra viruses, indicating that these viruses may be present in the geographic distribution of Pteropodidae bats in Africa.
Nipah virus outbreaks in pigs and other domestic animals, including horses, goats, lambs, cats, and dogs, were first put on record during the 1999 Malaysian outbreak. The virus is quite infectious in pigs. Pigs are contagious during the incubation period, which lasts between 4 and 14 days. An infected pig may not show any signs, but others develop acute feverish sickness, hard breathing, and neurological symptoms such as trembling, twitching, and muscle spasms.
Except for young piglets, mortality is often minimal. These symptoms are similar to those seen in other pig respiratory and neurological disorders. Nipah virus should be considered if pigs exhibit an unusual barking cough or if human instances of encephalitis are reported.
Currently, there are no vaccinations available for the Nipah virus. Based on the experience obtained during the 1999 Nipah outbreak involving pig farms, routine and thorough cleaning and disinfection with proper detergents may be effective in preventing infection. If an outbreak is suspected, quarantine the animal premises immediately. Culling sick animals, with careful supervision of burial or cremation of corpses, may be required to limit the danger of transmission to humans.
Restricting or prohibiting the transportation of animals from affected farms to other locations may help to slow the disease’s spread. Because Nipah virus outbreaks have implicated pigs and/or fruit bats, building an animal health/wildlife surveillance system using a One Health approach to detect Nipah cases is critical for providing early warning to veterinary and human public health authorities.
Public Health and Safety Measures
In the absence of a vaccine, the only option to limit or prevent infection in people is to raise awareness of the risk factors and educate them on how to reduce their exposure to the Nipah virus. Efforts to avoid transmission should begin with limiting bat access to date palm sap and other fresh food sources. Protecting bats from sap collection sites with protective coverings (such as bamboo sap skirts) may be beneficial.
Handling sick animals or their tissues, as well as slaughtering and culling procedures requires the use of gloves and other protective apparel. As much as possible, people should avoid contact with diseased pigs. When building new pig farms in endemic areas, examine the existence of fruit bats in the area, and in general, protect pig feed and pig sheds from bats whenever possible. Avoid close, unprotected physical contact with anyone sick with the Nipah virus. After caring for or visiting sick persons, it is important to wash your hands frequently.
Health-care staff caring for patients with suspected or proven infection, or handling specimens from them, should always use conventional infection control precautions. Human-to-human transmission has been documented, particularly in health-care settings, thus contact and droplet measures should be implemented in addition to conventional precautions. Airborne precautions may be required in certain situations. Samples collected from humans and animals with suspected Nipah virus infection should be handled by competent personnel working in properly equipped laboratories.
Global Health Recommendations and Future Research
WHO provides technical recommendations to affected and at-risk nations on how to manage and prevent Nipah virus outbreaks. The threat of worldwide transmission via fruits or fruit products (such as raw date palm juice) contaminated with infected fruit bat urine or saliva can be reduced by carefully washing and peeling them before consumption. Fruit showing symptoms of bat bites should be discarded.