It was first
identified in fruit bats of the Pteropodidae family, which are also the natural hosts
of the virus.
Out of an estimated
582 human cases of Nipah virus, 54 percent were fatal.
Signs and symptoms
The symptoms start to appear within
3–14 days after exposure. Initial symptoms are fever, headache, drowsiness
followed by disorientation and mental confusion.
These symptoms can progress into coma
as fast as in 24–48 hours. Encephalitis is the dreaded complication of nipah
virus infection.
Respiratory illness can also be
present during the early part of the illness. Nipah-case patients who had
breathing difficulty are more likely than those without respiratory illness to
transmit the virus.
The disease is suspected in
symptomatic individuals in the context of an epidemic outbreak.
Diagnosis and Tests
Laboratory diagnosis of Nipah virus infection is made
using real time polymerase chain reaction (RT-PCR) from throat swabs, cerebrospinal fluid, urine and blood
analysis during acute and convalescent stages of the disease.
Immunohistochemistry on
tissues collected during autopsy also confirms the disease. Viral RNA can
be isolated from the saliva of infected persons.
Treatment
Currently there is no effective treatment for Nipah virus
infection. The treatment is limited to supportive care.
It is important to practice standard infection control
practices and proper barrier nursing techniques to avoid the transmission of
the infection from person to person.
All suspected cases of Nipah virus infection should be
isolated and given intensive supportive care. Ribavirin has been shown
effective in in vitro tests, but has not yet been proven
effective in humans.
Passive immunization using a human monoclonal antibody
that targets the Nipah G glycoprotein has been evaluated in the ferret model as
post-exposure prophylaxis.
The anti-malarial drug chloroquine was shown to block the
critical functions needed for maturation of Nipah virus, although no clinical
benefit has yet been observed.
m102.4, a human monoclonal antibody, has been used in
people on a compassionate use basis in Australia and is presently in
pre-clinical development.
Prevention
Prevention of Nipah virus infection is important since
there is no effective treatment for the disease.
The infection can be prevented by avoiding exposure to
bats in endemic areas and sick pigs.
Drinking of raw palm sap (palm toddy) contaminated by bat excretes, eating
of fruits partially consumed by bats and using water from wells infested by
bats should be avoided.
Bats are known to drink toddy that is collected in open
containers, and occasionally urinate in it, which makes it contaminated with
the virus.
Surveillance and awareness are important for preventing
future outbreaks. The association of this disease within reproductive cycle of
bats is not well studied. Standard infection control practices should be
enforced to prevent nosocomial infections.
A subunit vaccine using the Hendra G protein was found to
produce cross-protective antibodies against henipavirus and nipavirus has been
used in monkeys to protect against Hendra virus, although its potential for use
in humans has not been studied.
Risk of exposure
Fruit
bats are the natural reservoirs of Nipah virus
The risk of exposure is high for
hospital workers and caretakers of those infected with the virus.
In Malaysia and Singapore, Nipah
virus infection occurred in those with close contact to infected pigs.
In Bangladesh and India, the disease
has been linked to consumption of raw date palm sap (toddy) and contact with
bats.
Outbreaks
The highest mortality due to Nipah virus infection has
occurred in Bangladesh. In Bangladesh, the outbreaks are typically seen in
winter season.
Nipah virus first appeared in Malaysia in 1998 in
peninsular Malaysia in pigs and pig farmers.
By mid-1999, more than 265 human cases of encephalitis,
including 105 deaths, had been reported in Malaysia, and 11 cases of either
encephalitis or respiratory illness with one fatality were reported in
Singapore. In 2001, Nipah virus was reported from Meherpur District, Bangladesh and Siliguri, India.
The outbreak again appeared in 2003, 2004 and 2005
in Naogaon District, Manikganj District, Rajbari District, Faridpur District and Tangail District.
In Bangladesh, there were outbreaks in subsequent years as
well. For the first time in India, an outbreak has been reported in
the Kozhikode district of Kerala.
Ten deaths have been recorded, including one healthcare
worker. Those who have died are mainly from the districts of Kozhikode and
Malappuram, including a 31-year-old nurse, who was treating patients infected
with the virus.
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