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Sr. Executive / Executive, Production; THE IBN SINA PHARMACEUTICAL IND LTD

 Outbreak of Nipah Virus Infection in Bangladesh
Update: 2011-02-08

Nipah virus Encephalitis strikes again in Bangladesh in the region of Rangpur and Lalmonirhat. According to a source of government, 16 people died of the disease in last few days and 23 people are taking treatment at Rangpur Medical College and Hospital (RMCH) and Hatibandha Sadar Hospital. Nipah Virus Infection (NiV) is an emerging infectious disease of public health importance in the South-East Asia Region.

The outbreak of Nipah virus was first observed in September 1998 on pig farms in peninsular Malaysia and it resulted in 105 human deaths and the culling of one million pigs. 11 cases of nipah virus infection and one death occurred in the abattoir workers of Singapore when they were exposed to pigs exported from the affected Malaysian farms. Since 2001, human outbreaks and clusters of cases have been reported periodically in Bangladesh and neighboring region of northern India. Apart from pigs and human, Nipah virus is also prevalent in other domestic animals such as horses, goats, sheep, cats and dogs.

Nipah virus was discovered by Dr Chua Kaw Bing from the University of Malaya in March 1999.The name "Nipah" is taken after the place, Kampung Nipah in Negeri Sembilan where the virus was first isolated from humans in that area. The Nipah virus has been classified by the Centers for Disease Control and Prevention as a Category C agent. It is a new member of the paramyxovirus family. Based on seroprevalence data and virus isolations, the primary reservoir for Nipah virus is identified as Pteropid fruit bats including Pteropus vampyrus (Large Flying Fox) and Pteropus hypomelanus (Small Flying-fox)-both of which occur in Malaysia and the genus Pteropus giganteus is seen is Bangladesh. There is strong evidence that emergence of bat-related viral infection communicable to humans and animals have been attributed to the loss of natural habitats of bats. As the flying fox habitat is destroyed by human activity the bats get stressed and hungry, their immune system gets weaker, their virus load goes up and a lot of virus spills out in their urine and saliva.

The outbreak of the Nipah Virus in Malaysia and Singapore is mostly due to an increasing overlap between bat habitats and piggeries in peninsular Malaysia. At the index farm, fruit orchards were in close proximity to the piggery, allowing the spillage of urine, faeces and partially eaten fruit onto the pigs. Retrospective studies demonstrate that viral spillover into pigs may have been occurring in Malaysia since 1996 without detection .During 1998; viral spread was aided by the transfer of infected pigs to other farms where new outbreaks occurred. The transmission has occurred from the animals to human via respiratory droplets, throat and nasal secretion from the infected pigs or contact with the tissue of a sick animal. On the other hand, different transmission route is noticed in Bangladesh and India. The outbreaks in Bangladesh and India are mostly due transmission of the virus directly or indirectly from the infected bats to human. This occurs because of the consumption of fruits or fruit products (for example, raw palm juice) that has been contaminated by the infected fruit bats. Infected bats shed virus in their excretion and secretion such as saliva, urine, semen and excreta but they are symptomless carriers. Human to human transmission has also been observed in India in 2001 during the outbreak in Siliguri, 33 health workers and hospital visitors became ill after exposure to patients hospitalized with Nipah virus illness, suggesting nosocomial infection. Strong evidence indicative of human- to-human transmission of NiV was found in Bangladesh in 2004. Infected human sheds Nipah virus in upper respiratory secretions and urine.

Nipah virus disease in pigs is also known as porcine respiratory and neurologic syndrome, as well as barking pig syndrome. Nipah virus is highly contagious in pigs and it has been seen that the pigs are infectious during the incubation period, which lasts from 4 to 14 days. The symptoms seen in pigs include acute feverish illness, labored breathing, and neurological symptoms such as trembling, twitching and muscle spasms. The symptoms have no difference from other respiratory and neurological illness of pigs. Thus Nipah virus infection should be suspected if pigs show unusual barking coughs.

Nipah virus infection in human has similar symptoms to that of influenza and encephalitis depending on the severity of infection. The incubation period of NiV infection in human varies from 4 to 45 days. The usual one ranges from 4 to 20 days. Also 2 days or a month long incubation period has been observed. Some people may remain asymptomatic during initial infection, but develop serious neurological disease up to four years or later. The initial signs include fever, headaches, myalgia (muscle pain), vomiting and sore throat. These are followed by either acute or late onset of encephalitis and the symptoms include dizziness, drowsiness, altered consciousness, neurological signs, disorientation, convulsion, and coma. Most people survive acute encephalitis make a full recovery. 20% are left with residual neurological consequences such as convulsions and personality changes. In rare cases, patient develops delayed onset encephalitis. Persistent neurological dysfunction observed a more than 15% of people. Further, those who may have recovered from an acute episode may also have a relapse. Septicemia, bleeding from the gastrointestinal tract, renal impairment and other complications can occur in severely ill patients. Cases that have progressed to encephalitis are often fatal. The case fatality rate ranges from 9 to 75%. Less often, patients develop respiratory signs, which may include acute respiratory distress syndrome.

Nipah virus is most likely to be recovered from clinical samples early in the illness. This virus is classified as a biosafety level 4 (BSL4) pathogen, which restricts the number of laboratories able to perform virus isolation. Nipah virus infection can be diagnosed by a number of different tests such as serum neutralization, enzyme-linked immunosorbent assay (ELISA), polymerase chain reaction (PCR) assay, immunofluorescence assay and virus isolation by cell culture.

Currently there are no drugs or vaccines available to treat Nipah virus infection. Intensive supportive care with treatment of symptoms is the main approach to managing the infection in people. Some infected individuals who received the antiviral drug ribavirin early in their illness had less severe symptoms. Treatment is mostly focused on managing fever and the neurological symptoms. Severely ill individuals will be hospitalized and may require the use of a respirator (ventilator).

NiV infection in domestic animals can be prevented by routine cleaning and disinfection of pig farms (with sodium hypochorite or other detergents) and this mode of control is expected to 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 to detect new cases is essential in providing early warning for veterinary and human public health authorities.

The risk of infection in people can be reduced by raising awareness of the risk factors and educating people about the measures they can take to reduce exposure to the virus. 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. Freshly collected date palm juice should also be boiled and fruits should be thoroughly washed and peeled before consumption.
  • Reducing the risk of human-to-human transmission. Close physical contact with Nipah virus-infected people should be avoided. Gloves and protective equipment should be worn when taking care of ill people. Regular hand washing should be carried out after caring for or visiting sick people.
  • Nipah virus is readily inactivated by soaps, detergents and many disinfectants. Routine cleaning and disinfection with sodium hypochlorite or commercial available disinfectants is expected to be available.
  • 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.
  • Controlling infection in health-care settings. Health-care workers caring for patients with suspected or confirmed Nipah virus infection, or handling specimens from them, should implement standard infection control precautions. Samples taken from people and animals with suspected Nipah virus infection should be handled by trained staff working in suitably equipped laboratories.
The outbreak of NiV infection can only be stopped by adopting correct prevention strategies. Establishing appropriate surveillance systems will be necessary so that NiV outbreaks can be detected quickly and appropriate control measures initiated.
B.Pharm(North South University)
Research Executive, Viola Vitalis,Bangladesh.

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