NIPHA VIRUS: A NEW BIOLOGICAL ENEMY OF MANKIND

Nipah virus (NiV) disease in pigs is also known as “Porcine respiratory” and “Neurologic syndrome” as well as barking pig syndrome based on clinical observation. The virus is named after the Malaysian village Sungai Nipah, Where it was first discovered in 1999. This virus along with Hendra virus comprises a new genus designated Henipavirus in the subfamily Paramyxovirinae.

Reservoir of NiV

Reservoir of virus Fruit bats of the genus Pteropus (Flying foxes) was identified as natural reservoirs of NiV. The seroepidemiologic study in Malaysia implicated four fruit bat species, Pteropus hypomelanus, P. vampyrus, Cynopterus brachyotis, Eonycteris spelaea, and an insectivorous bat Scotophilus kuhlii.

Isolation of NiV

Nipah virus can be isolated from the brain and spinal fluid of victims. Infective virus was isolated from environmental samples of bat urine and partially-eaten fruit.

Fatality

Case fatality rate of NiV ranges from 40-70% although it has been as high as 100% in some outbreaks. In india % of fatality-

Feb 2001	66%
Jan-Feb 2007	43%
Mar-Apr 2007	63%
April 2007	100%

Note- Recently on 22^nd May 2018, a news report from kozhikode kerala reported about 10 people who were infected by NiV. Out of these 10 people, 8 were dead by that time and rest of 2 were in very serious condition on ventilator. Among those 10 people, 4 were from same family which was infected by eaten fruit.

Mode of transmission

The mode of transmission Infected bats shed virus in their excretion and secretion such as saliva, urine, semen and excreta but they are symptomless carriers. The NiV is highly contagious among pigs, spread by coughing. Direct contact with infected pigs was identified as the predominant mode of transmission in humans when it was first recognized in a large outbreak in Malaysia in 1999.

Symptoms

Symptoms of NiV infection in humans are similar to that of influenza such as fever and muscle pain. In some cases, inflammation of the brain occurs leading to disorientation or coma. Encephalitis may present as acute or late onset.

Diagnosis

• Enzyme-linked immunosorbent assay (ELISA)
• Polymerase chain reaction (PCR) assay

• Virus isolation by cell culture.

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:

Prevention and control

Ø  There is no effective treatment for Nipah virus disease.

Ø  However Ribavarin may alleviate the symptoms of nausea, vomiting, and convulsions. Treatment is mostly focused on managing fever and the neurological symptoms. Ribavirin is a prodrug, which when metabolized resembles purine RNA nucleotides.

Ø  A vaccine named ALVAC developed in Canada was tested on cats and was found to be effective against Nipah virus. This recombinant sub-unit vaccine formulation protected cats against this lethal virus, appears to be a promising vaccine for humans.⃰

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

Source- WHO Asia-Pacific Region, Collaborating Centre for Viral Zoonoses, Division of Neurovirology, Chulalongkorn University, Bangkok, Thailand.

⃰ According to the journal of virology.