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Nipah Virus Infection

Nipah virus (NiV) infection is a newly emerging zoonosis (disease or infection that is naturally transmissible from vertebrate animals to humans) that causes severe disease in both animals and humans.

Nipah virus is closely related to Hendra virus. Both are members of the genus Henipavirus, a new class of virus in the Paramyxoviridae family.

Key facts

  • Nipah virus is an RNA virus that is part of the Paramyxovidae family that was first identified as a zoonotic pathogen after an outbreak involving severe respiratory illness in pigs and encephalitic disease in humans in Malaysia and Singapore in 1998 and 1999.
  • Nipah virus can cause a range of mild to severe disease in domestic animals such as pigs.
  • Nipah virus infection in humans causes a range of clinical presentations, from asymptomatic infection (subclinical) to acute respiratory infection and fatal encephalitis.
  • Nipah virus can be transmitted to humans from animals (bats, pigs), and can also be transmitted directly from human-to-human.
  • Fruit bats of the Pteropodidae family are the natural host of Nipah virus.
  • There is no treatment or vaccine available for either people or animals.
  • The primary treatment for humans is supportive care.
  • Nipah virus is on the WHO list of Blueprint priority diseases

Transmission

The natural host of the virus are fruit bats of the Pteropodidae Family, Pteropus genus.

NiV was first identified during an outbreak of disease that took place in Kampung Sungai Nipah, Malaysia in 1998. On this occasion, pigs were the intermediate hosts.However, in subsequent NiV outbreaks, there were no intermediate hosts.

In Bangladesh in 2004, humans became infected with NiV as a result of consuming date palm sap that had been contaminated by infected fruit bats.

Human-to-human transmission has also been documented, including in a hospital setting in India.

Symptoms

Human infections range from asymptomatic infection, acute respiratory infection (mild, severe), and fatal encephalitis. Infected people initially develop influenza-like symptoms of fever, headaches, myalgia (muscle pain), vomiting and sore throat. This can be followed by dizziness, drowsiness, altered consciousness, and neurological signs that indicate acute encephalitis. Some people can also experience atypical pneumonia and severe respiratory problems, including acute respiratory distress. Encephalitis and seizures occur in severe cases, progressing to coma within 24 to 48 hours.

The incubation period (interval from infection to the onset of symptoms) is believed to range between from 4-14 days. However an incubation period as long as 45 days has been reported.

Most people who survive acute encephalitis make a full recovery, but long term neurologic conditions have been reported in survivors.  Approximately 20% of patients are left with residual neurological consequences such as seizure disorder and personality changes. A small number of people who recover subsequently relapse or develop delayed onset encephalitis.

The case fatality rate is estimated at 40% to 75%; however, this rate can vary by outbreak depending on local capabilities for epidemiological surveillance and clinical management.

Diagnosis

Initial signs and symptoms of NiV infection are non-specific and the diagnosis is often not suspected at the time of presentation.  This can hinder accurate diagnosis and creates challenges in outbreak detection and institution of effective and timely infection control measures and outbreak response activities.

In addition, clinical sample quality, quantity, type, timing of collection and the time necessary to transfer samples from patients to the laboratory can affect the accuracy of laboratory results.

NiV infection can be diagnosed together with clinical history during the acute and convalescent phase of the disease. Main tests including real time polymerase chain reaction (RT-PCR) from bodily fluids as well as antibody detection via ELISA.  Different tests include:

  • enzyme-linked immunosorbent assay (ELISA)
  • polymerase chain reaction (PCR) assay
  • ·virus isolation by cell culture.

Treatment

There are currently no drugs or vaccines specific for NiV infection although this is a priority disease on the WHO R&D Blueprint.  Intensive supportive care is recommended to treat severe respiratory and neurologic complications.

Natural host: fruit bats

Fruit bats of the family Pteropodidae – particularly species belonging to the Pteropus genus – are the natural hosts for Nipah virus. There is no apparent disease in fruit bats.

It is assumed that the geographic distribution of Henipaviruses overlaps with that of Pteropus category. This hypothesis was reinforced with the 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, were found positive for antibodies against Nipah and Hendra viruses, indicating that these viruses might be present within the geographic distribution of Pteropodidae bats in Africa.

Nipah virus in domestic animals

Nipah outbreaks in pigs and other domestic animals (horses, goats, sheep, cats and dogs) were first reported during the initial Malaysian outbreak in 1999.

Nipah virus is highly contagious in pigs. Pigs are infectious during the incubation period, which lasts from 4 to 14 days.

An infected pig can exhibit no symptoms, but some develop acute feverish illness, labored breathing, and neurological symptoms such as trembling, twitching and muscle spasms. Generally, mortality was low except in young piglets. These symptoms are not dramatically different from other respiratory and neurological illnesses of pigs. Nipah should be suspected if pigs also have an unusual barking cough or if human cases of encephalitis are present.

Prevention

Controlling Nipah virus in domestic animals

Currently, there are no vaccines available against Nipah virus. Routine and thorough cleaning and disinfection of pig farms (with appropriate detergents) may be effective in preventing infection.

If an outbreak is suspected, the animal premises should be quarantined immediately.  Culling of infected animals – with close supervision of burial or incineration of carcasses – may be necessary to reduce the risk of transmission to people. Restricting or banning the movement of animals from infected farms to other areas can reduce the spread of the disease.

As Nipah virus outbreaks in domestic animals have preceded human cases, establishing an animal health surveillance system, using a One Health approach, to detect new cases is essential in providing early warning for veterinary and human public health authorities.

Reducing the risk of infection in people

In the absence of a licensed vaccine, the only way to reduce infection in people is by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to and decrease infection from NiV.

Public health educational messages should focus on the following:

  • Reducing the risk of bat-to-human transmission: Efforts to prevent transmission should first focus on decreasing bat access to date palm sap and to other fresh food products. Keeping bats away from sap collection sites with protective coverings (e.g., bamboo sap skirts) may be helpful.Freshly collected date palm juice should be boiled and fruits should be thoroughly washed and peeled before consumption.
  • Reducing the risk of animal-to-human transmission: Gloves and other protective clothing should be worn while handling sick animals or their tissues, and during slaughtering and culling procedures. As much as possible, people should avoid being in contact with infected pigs.
  • Reducing the risk of human-to-human transmission: Close unprotected physical contact with Nipah virus-infected people should be avoided. Regular hand washing should be carried out after caring for or visiting sick people.

Controlling infection in health-care settings

  • Health-care workers caring for patients with suspected or confirmed NiV infection, or handling specimens from them, should implement standard infection control precautions for all patients at all times
  • As human-to-human transmission in particular nosocomial transmission have been reported, contact and droplet precautions should be used in addition to standard precautions.
  • Samples taken from people and animals with suspected NiV infection should be handled by trained staff working in suitably equipped laboratories.

Source : WHO

Nipah virus - video for the deaf

Nipah virus infection in Kerala

First symptomatic case of Nipah virus infection manifested on 2nd May 2018 near Perambra in Kozhikode district of Kerala. The index case was a 26 - year - old male who initially presented with fever, myalgia and respiratory distress. He died in Calicut Medical College, Kerala within the next few days. Subsequently, four other family members and close contacts were admitted within the next two days, of which three tested positive for Nipah virus at Manipal Centre for Virus Research and were subsequently confirmed at ICMR - National Institute of Virology, Pune.

As on May 31, 2018, there are 19 reported cases (18 lab confirmed). Out of 19 reported cases 17 died, from the two affected districts of Kozhikode and Malappuram in Kerala State. The Kerala State Govt. as well as the Union Ministry of Health & Family Welfare have immediately come into action. Steps taken are as follows:

  • The Kerala Govt. has ensured adequate ICU/hospital isolation wards facilities for all suspect Nipah cases.
  • Adequate supply of personal protective equipment (PPE) has been arranged for health care workers.
  • Contact tracing of the index case, secondary cases and contacts has been done. All the contacts are kept under close supervision and being monitored for the next 42 days.
  • Pigs have been isolated and surveillance in pigs and other domestic animals has been initiated.
  • The Govt. of Kerala is also exploring various treatments for NiV infection.
  • MCVR, Manipal and NIV, Pune are well equipped with Nipah diagnostics to cope up with the increased Nipah testing load.
  • The NIV, Field Unit at Allapuzha, Kerala has been equipped with diagnostics for Nipah testing.

Advice to people:

  • Avoid eating half bitten fruits or fruits dropped on the ground.
  • Frequent hand washing with soap and water is recommended.
  • Avoid contact with bats, pigs and pig handlers.

Guidelines issued by Government of India

The Government of India has issued the following guidelines.



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