Nipah

There's a real, deadly virus.

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bats. getty

Nipah virus was the inspiration for the virus in the movie Contagion. It’s a real virus. It's also an exceptionally deadly one.

Fortunately, only a dozen or so Nipah outbreaks have ever been known to occur. This has led to a few hundred cases total, with around 300 cases in the largest outbreak.

The problem is the disease can be very deadly. It is an exceptionally deadly disease with mortality rates in the 50-75% rate, rivaling Ebola.

There is no specific treatment for Nipah. No vaccine, no cure.

In the movie, Nipah Virus (Niv) is a bit different than it actually is. Hollywood changed the story a bit. In the movie, the virus seems like an awful case of the flu, but it's supposed to be Nipah merged with influenza, making Nipah more easily spread. Fortunately, this merger of these viruses is not likely.

What's the story?

Nipah was first seen in Malaysia in 1998 in pig farmers. It was mistaken at first for another virus, Japanese Encephalitis. Both diseases lead to encephalitis, or brain swelling, which can cause seizures, coma, and other neurologic problems. A mosquito control campaign to stop Japanese Encephalitis failed to stop the encephalitis that was actually Nipah - and not spread by mosquitoes.

However, those who were sick had close contact with pigs (86% reported handling a pig, half of the pigs were noted to be sick).

The link was made, but the disease had spread. The pigs were routinely transported between farms and abattoirs (slaughterhouses), which had spreadthe infection further. The outbreak affected in Malaysia and across the border in Singapore. To end the spread of the disease, close to 1 million pigs were culled and transport of pigs was banned while abattoirs were closed.

By that point over 100 had died and about 300 infected. The disease was not seen again in Malaysia.

Then the disease showed up in Bangladesh in 2004, where there weren't pig farms. People were pretty much uniformly Muslim and did not eat pork.

With a bit of investigation, it turned out the Bangladesh cases were due to - of all things - date palm sap. This sweet sap had been contaminated by fruit bat droppings. The bats, it seemed, liked the sweet sap as much as the people who harvested it.

Multiple outbreaks have occurred since 2001, almost every year up until 2011. 9 cases have been identified in 2015. All of these outbreaks have occurred in Bangladesh and India. Most infections occur in a Nipah band in Bangladesh.

The cases in Malaysia were more encephalitic (affecting the brain) while those in Bangladesh were  more respiratory. The Malaysian cases did not appear to spread person-to-person. In Bangladesh and India, the infection has spread from patient to caregiver, whether in the home or in a clinic or hospital.

One doctor is known to have died from taking care of Nipah patients.

What does it cause?

Nipah Virus can cause mild or asymptomatic disease - or it can cause fever, headache, dizziness, and vomiting. This can progress to problems breathing, brain swelling (encephalitis) causing loss of consciousness and/or seizures, and death. The encephalitis can be particularly serious and difficult to treat.

The disease can cause a serious vasculitis, or inflammation of the vessels, in the brain, as well as brain lesions. It can cause particular problems such as 'segmental myoclonus' -, and lack of reflexes (areflexia) and lack of muscle tone.

The disease can relapse, months or years later. Many have recurrent symptoms, including some who had initially mild symptoms.

Many others are left with permanent neurologic deficits.

How does it spread?

So far, transmission routes have been fairly limited: 

a) Handling pigs, especially sick pigs

b) Eating, drinking raw date palm sap

c) Caring for someone ill with Nipah (at home or in a hospital or clinic)

d) Preparing a body that had died from Nipah

The virus is found naturally in flying foxes - fruit bats. It's important to avoid contact with bats or their excreta anywhere - but especially where Nipah is found.

The virus can spread from person-to-person so be sure to involve medical professionals and the correct precautions if Nipah is suspected.

There can be many other ways the disease is spread. Anything which bat droppings can contaminate might spread it. Other animals, like pigs, could potentially become secondary hosts.

There can be simple ways to protect against Nipah. Bamboo skirts to protect the date palm sap being harvested from bat contamination.

What treatment is there?

There is no specific treatment. Treatment is usually supportive - including help with breathing (oxygen, ventilation), hydration (fluids), and other intensive care. There has been investigation into whether ribavirin can help treat Nipah. The drug, which has been used in other viruses, may make the encephalitis less severe.

Pigs and other animals can also become sick and may be culled, as they have been in Malaysia.

Where is the virus?

The virus has been identified in not just Malaysia, Signapore, Bangladesh, and India, where there have been outbreaks.

Antibodies to the virus was still seen in bats in Malaysia after the last human infections, but there have been no subsequent outbreaks.

Antibodies against the virus have been found in the same bats in Thailand, Cambodia (including at restaurants), and in similar bats, West African fruit bats, in Ghana as well as other bats in Madagascar. However, no human (or other animal) cases have been seen in these countries.

Why now?

The virus has only recently been identified (in 1998). Likely there were cases before, but surveillance and testing were not able to identify these. 

It may be, though, that humans are accelerating its spread. When humans move to the edge of a forest where bats live, they may be exposed more to bat diseases. When people cut down the trees where bats live and eat, they may be at even further risk. Bats may be more likely to seek food and a place to sleep closer to humans. Forests may be cut down leaving fragmented sections of trees between villages, forcing bats and humans closer together.When forests where bats live are encroached upon, humans are at greater risk from bat diseases, like Nipah.

In Malaysia, large commercial pig farms were expanding. These farms were often close to forested areas that were being cut down or orchards, where bats lived and ate. The bats could eat fruit, dropping bits into the farms where pigs lived, thus spreading the disease through fruit. The commercial trade of pigs led to the dispersal of the disease even further.

In Bangladesh, the Nipah belt occurs where trees have been taken down where bats once lived. Those villages between areas of fragmented forest rather than intact forest may be at greater risk.

What precautions are needed?

It's important that caregivers keep themselves safe and do not become infected. In the case of Nipah, standard, contact, and droplet precautions are needed. This includes, among other steps, wearing gloves and a simple mask to avoid becoming infected.

How is it diagnosed?

The disease often occurs in outbreaks. Similar cases may be diagnosed clinically.

New outbreaks and confirmation of diagnoses can be based on PCR testing of throat or nasal swabs, CSF (cerebrospinal fluid), urine, or blood tests even in early stages of the illness. Antibodies can be detected later on. Immunohistochemistry can be performed on tissue samples (such as from an autopsy). Such testing - PCR, Antibody, and immunohistochemistry may not be available in remote areas where the infection often occurs. 

When does it occur?

Outbreaks usually occur in the winter. The season last from December to May.

Why is it called Nipah?

The virus was named after where the first outbreak occurred - in Kampung Sungai Nipah, Malaysia. 

Is there a vaccine?

There isn't a vaccine currently. However, there is hope that a vaccine developed for a similar virus, Hendra, which has been affecting horses in Australia, could help prevent Nipah. This is a subunit vaccine, using the Hendra G protein, that creates antibodies protective against both Hendra and Nipah. 

What sort of virus is Nipah?

Nipah is a member of the family Paramyxoviridae, genus Henipavirus. This genus includes Hendra virus, which has caused disease in humans and horses in Australia, as well as Cedar virus, which doesn't seem to be a problem. Many viruses are in the family Paramyxoviridae - such as, measles, parainfluenza, metapneumovirus.

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