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Nipah virus (NiV) is a member of the family Paramyxoviridae, genus Henipavirus. NiV was initially isolated and identified in 1999 during an outbreak of encephalitis and respiratory illness among pig farmers and people with close contact with pigs in Malaysia and Singapore. Its name originated from Sungai Nipah, a village in the Malaysian Peninsula where pig farmers became ill with encephalitis. Given the relatedness of NiV to Hendra virus, bat species were quickly singled out for investigation and flying foxes of the genus Pteropus were subsequently identified as the reservoir for NiV.

Note : All Details Have Been Taken From WHO Official Website & Center for disease control and prevention(CDC) Official Website to Create Awareness Among People. All Credits Goes To WHO Website & CDC Website.

Nipah Virus History

Nipah virus infection was first recognized in a large outbreak of 265 suspected cases in peninsular Malaysia during September 1998 to April 1999. Most patients had contact with sick pigs or had been in close physical contact with Nipah virus infected patients and then presented primarily with encephalitis. The outbreak was initially thought to be due to Japanese encephalitis, but it was later identified as Nipah virus encephalitis. This outbreak caused widespread panic and fear in Malaysia leading to considerable social disruptions and tremendous economic loss because of the mass culling of over one million pigs. In addition, eleven abattoir workers in Singapore developed a febrile illness caused by Nipah virus during March 1999 following close contact with imported pigs from Malaysia. The presentation of Nipah virus infection has been variable, ranging from the high mortality observed in the original Malaysian outbreak to an outbreak of low mortality disease among abattoir workers in Singapore, which presented as neurological illness and atypical pneumonia. No new outbreaks have been reported from these countries since May 1999.

Morbidity and mortality due to Nipah or Nipah-like virus encephalitis, South-East Asia Region, 2001-2012

Year/Month Location No. cases No. deaths Case Fatality Rate
Jan-Feb 2001 Siliguri (India) 66 45 68%
Apr-May 2001 Meherpur (Bangladesh) 13 9 69%
Jan-03 Naogaon (Bangladesh) 12 8 67%
Jan  2004 Rajbari( Bangladesh) 31 23 74%
Apr-04 Faridpur (Bangladesh) 36 27 75%
Jan-Mar 2005 Tangail (Bangladesh) 12 11 92%
Jan-Feb 2007 Thakurgaon (Bangladesh) 7 3 43%
Mar-07 Kushtia,Pabna,Natore (Bangladesh) 8 5 63%
Apr-07 Naogaon (Bangladesh) 3 1 33%
Apr-07 Nadia (India) 5 5 100%
Feb-08 Manikgonj (Bangladesh) 4 4 100%
Apr-08 Rajbari and Faridpur (Bangladesh) 7 5 71%
Jan-09 Gaibandha, Rangpur and Nilphamari (Bangladesh) 3 0 0%
Rajbari (Bangladesh) 1 1 100%
Feb-Mar 2010 Faridpur, Rajbari,Gopalganj,Madaripur (Bangladesh) 16 14 87.50%
Jan-Feb 2011 Lalmohirhat, Dinajpur, Comilla, Nilphamari and Rangpur (Bangladesh) 44 40 91%
Feb-12 Joypurhat, Rajshahi, Natore, Rajbari and Gopalganj (Bangladesh) 12 10 83%
Total   280 211 75%
 

 Nipah Virus 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

Nipah Virus 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.

Nipah Virus Transmission

Transmission of Nipah virus to humans may occur after direct contact with infected bats, infected pigs, or from other NiV infected people.

In Malaysia and Singapore, humans were apparently infected with Nipah virus only through close contact with infected pigs. The NiV strain identified in this outbreak appeared to have been transmitted initially from bats to pigs, with subsequent spread within pig populations. Incidental human infections resulted after exposure to infected pigs. No occurrence of person-to-person transmission was reported in this outbreak.

Conversely, person-to-person transmission of Nipah virus in Bangladesh and India is regularly reported. This is most commonly seen in the family and caregivers of Nipah virus-infected patients. Transmission also occurs from direct exposure to infected bats. A common example is consumption of raw date palm sap contaminated with infectious bat excretions.

Nipah Virus Signs and Symptoms

Infection with Nipah virus is associated with encephalitis (inflammation of the brain). After exposure and an incubation period of 5 to 14 days,illness presents with 3-14 days of fever and headache, followed by drowsiness, disorientation and mental confusion. These signs and symptoms can progress to coma within 24-48 hours. Some patients have a respiratory illness during the early part of their infections, and half of the patients showing severe neurological signs showed also pulmonary signs.

During the Nipah virus disease outbreak in 1998-99, 265 patients were infected with the virus. About 40% of those patients who entered hospitals with serious nervous disease died from the illness.

Long-term sequelae following Nipah virus infection have been noted, including persistent convulsions and personality changes.

Latent infections with subsequent reactivation of Nipah virus and death have also been reported months and even years after exposure.

Nipah Virus Risk of Exposure

In the Malaysia and Singapore outbreak, Nipah virus infection was associated with close contact with Nipah virus-infected pigs.

In Bangladesh and India, where Nipah virus infection is more frequent, exposure has been linked to consumption of raw date palm sap and contact with bats. Importantly, human-to-human transmission has been documented and exposure to other Nipah virus infected individuals is also a risk factor.

Nipah Virus Diagnosis

Laboratory diagnosis of a patient with a clinical history of NiV can be made during the acute and convalescent phases of the disease by using a combination of tests. Virus isolation attempts and real time polymerase chain reaction (RT-PCR) from throat and nasal swabs, cerebrospinal fluid, urine, and blood should be performed in the early stages of disease. Antibody detection by ELISA (IgG and IgM) can be used later on. In fatal cases, immunohistochemistry on tissues collected during autopsy may be the only way to confirm a diagnosis.

Nipah Virus Treatment

Treatment is limited to supportive care. Because Nipah virus encephalitis can be transmitted person-to-person, standard infection control practices and proper barrier nursing techniques are important in preventing hospital-acquired infections (nosocomial transmission).

The drug ribavirin has been shown to be effective against the viruses in vitro, but human investigations to date have been inconclusive and the clinical usefulness of ribavirin remains uncertain.

Passive immunization using a human monoclonal antibody targeting the Nipah G glycoprotein has been evaluated in the post-exposure therapy in the ferret model and found to be of benefit.

Nipah Virus Prevention

Nipah virus infection can be prevented by avoiding exposure to sick pigs and bats in endemic areas and not drinking raw date palm sap.

Additional efforts focused on surveillance and awareness will help prevent future outbreaks. Research is needed to better understand the ecology of bats and Nipah virus, investigating questions such as the seasonality of disease within reproductive cycles of bats. Surveillance tools should include reliable laboratory assays for early detection of disease in communities and livestock, and raising awareness of transmission and symptoms is important in reinforcing standard infection control practices to avoid human-to-human infections in hospital settings (nosocomial infection).

A subunit vaccine, using the Hendra G protein, produces cross-protective antibodies against HENV and NIPV has been recently used in Australia to protect horses against Hendra virus. This vaccine offers great potential for henipavirus protection in humans as well.

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.

Note : All Details Have Been Taken From WHO Official Website & Center for disease control and prevention(CDC) Official Website to Create Awareness Among People. All Credits Goes To WHO Website & CDC Website.

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