Striking a Familiar Zoonotic Pathogen Chord

International arrivals at Suvarnabhumi International Airport in Bangkok face extra screenings following the outbreak in India. (Suvarnabhumi Airport Office /Handout via Reuters)

"Nipah virus (NiV) is a member of the Henipavirus genus of the Paramyxoviridae family and is a zoonotic virus with a high case fatality rate. Our knowledge of the geographic distribution of NiV and the disease it causes, mode of pathogen transmission, and clinical manifestations of infection, have evolved over time."

"The first recognized human infection was in the Malaysian village of Kampung Sungai Nipah in 1998, initiating a deadly outbreak that lasted through 1999. Smaller sporadic outbreaks have since recurred nearly annually within South Asia with case fatality rates reaching greater than 90%."

National Library of Medicine...National Center for Biotechnology Information 

Black flying fox bats ... World Health Organization

 

Nipah virus infection in humans causes a range of clinical presentations, from asymptomatic infection (subclinical) to acute respiratory infection and fatal encephalitis.

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

Nipah virus can be transmitted to humans from animals (such as bats or pigs), or contaminated foods 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.

The 2018 annual review of the WHO R&D Blueprint list of priority diseases indicates that there is an urgent need for accelerated research and development for the Nipah virus. WHO 

Confirmation of an outbreak of Nipah virus in West Bengal, India, led to southwest Asia airports placed on alert. Checkpoints for passengers from West Bengal were implemented by Thailand on Sunday, while Taiwan's Centers for Disease Control announced that it planned to list the disease as a Category 5 threat. The Indian Ministry of Health confirmed two cases of the zoonotic infection, with 200 close contacts being monitored and tested. 

 

Nipah has a fatality rate of 40 to 70 percent, according to the Centers for Disease control and Prevention. No vaccine has yet been produced against the virus and there is no cure for Nipah virus. Outbreaks of Nipah occur annually in South Asia, while more broadly global awareness of the virus remains low. Transmitted to people from animals, the virus can be contracted from direct contact with infected animals, primarily flying fox bats and pigs.

Nipah virus has a fatality rate in humans of up to 75 per cent. (Reuters: CK Thanseer)

 

Fruit contaminated by these animals can be a source of infection for the unsuspecting. Raw date palm juice produced with sap contaminated by fruit  bats has been linked to outbreaks in Bangladesh. The virus, once it makes the leap from a contaminated animal's tissues or secretions, can readily spread person-to-person through close physical contact.

Scientists in Bangladesh have previously caught bats to test them for the virus. (Reuters: Mohammad Ponir Hossain, file)

 

A major outbreak among pig farmers in 1999 Malaysia killed over a hundred people, and this was the world's introduction to the presence of the virus,  highly contagious among pigs. Nipah outbreaks occur almost annually in Asia, most frequently in Bangladesh and India. A 'predictable season pattern' has emerged as routine outbreaks in Bangladesh between December and April, a research paper published in the Journal of Infection and Public Health established.

 

That research linked the pattern to peak harvesting season for raw date palm sap, a cultural delicacy and tradition, where fruit bats frequently live among date trees. The Philippines, Singapore and Malaysia have also been host to outbreaks. "This represents a return of Nipah to this area after a long gap, which is concerning from a surveillance standpoint", pointed out Lauren Sauer, director, Special Pathogen Research Network at University of Nebraska Medical Center.

 

Within days of infection symptoms including fever, headache, cough, muscle pain and difficulty breathing emerge. Patients may experience neurological symptoms such as  brain swelling as the infection progresses. Patients who survive brain swelling (encephalitis or brain inflammation) can recover but still face a future life of consequences including seizure disorders.

 

No licensed treatments exist for Nipah, nor are there any available vaccines.  

 

In 2018 the World Health Organization  marked Nipah as a priority pathogen urgently requiring accelerated research and development particular to the virus.