Written by Phillip Mazzotta
Nipah virus belongs to the family of viruses known as paramyxoviridae and genus henipavirus. Henipavirus include Hendra virus and Cedar virus along with Nipah virus. The virus was named after the place from where it was first isolated, Kampung Sungai Nipah, a village in Malaysia. Pigs were the intermediate hosts at the time of outbreak in 1999; however, it was soon found that subsequent NiV (Nipah virus) outbreaks had no more intermediate hosts.
Nipah virus causes encephalitis. The first outbreak was reported in 1999, Malaysia with more than 300 human cases and 100 deaths. In 2001 Nipah virus was again identified as a causative agent of a human disease occurring in Bangladesh. Genetic studies proved it to be the Nipah virus, but a strain different from the one recognized in 1999. Siliguri, India in the year 2001 witnessed another outbreak with person to person transmission of the virus this time.
Reservoir of the virus
It was found that the fruit bat of the family pteropus were the natural reservoirs of NiV. The infected agent has also been found in the environmental samples of fruit bat’s urine and partially eaten fruits in Malaysia.
Diagnosis and detection of the virus
A standard protocol has yet to be set for the detection of Nipah virus, but one of the common processes used currently is virus isolation from tissue samples. NiV from all the species can be detected from cerebrospinal fluid, kidneys and liver. Other practicable strategies are enzyme-linked immunosorbent, real time Polymerase chain reaction (RT-PCR) and immunofluorescence assays. Immunohistochemistry on the tissues becomes the only way to confirm the diagnosis in cases that are fatal.
Disease caused by Nipah virus and its symptoms
Nipah virus infection causes inflammation of brain, medically acknowledged as encephalitis. The incubation period of the virus ranges between 5-14 days. Illness is known to manifest between 3-14 days via headache, fever with subsequent drowsiness, mental confusion and disorientation. Progression of signs and symptoms to coma within 48 hours have also been reported. Some patients during early part of infection encountered respiratory illness and it was sorted out that half of the patients showing neurological signs also experienced pulmonary signs.
Around 300 patients were infected with the Nipah virus during 1998-99 outbreak, with a 40% death rate and the near collapse of the billion-dollar-pig farming industry.
Long term sequelae subsequent to viral infection has also been reported which includes personality changes and persistent infections.
Many cases showing latency of the virus and then reactivation leading to death have also been reported.
Transmission of the virus
Primarily bats and pigs infected with NiV were reported to be initial intermediate hosts and it was found that the virus was transmitted by direct contact with infected pigs and bats. Subsequent outbreaks showed that person to person transmission of NiV was also possible.
In Malaysia and Singapore, where initial outbreak was reported, the virus was only transmitted to humans by close contact with infected pigs. The strains of NiV identified in this outbreak were thought to be initially transferred from bats to pigs following further dissemination within pig’s population. These infected pigs were involved in incidental human infections. One of the important things to mention is no person to person transmission was reported during this outbreak.
On the other hand there are regular cases of person to person transmission in India and Bangladesh. The most common cases of person to person transmission are seen in families and caretakers of Nipah virus infected patients. Studies have confirmed that contact with an infected bat can also leave you vulnerable to the NiV virus. Example to this is, consumption of raw date palm sap that is befouled with infectious bat secretions.
Treatment and remedies
Up till now there is no treatment or vaccine which can be used as a therapy for NiV infection. The main goal is to treat the symptoms as effectively as possible in order to keep a check on infection. Vaccine against NiV is extremely difficult to synthesize because of the high mutation rate of RNA viruses as is true for most of the zoonotic diseases. On the other hand studies and researches have shown that targeting the G and F protein of the virus can prove to be efficacious as it will inhibit the binding of virus with the host cells.
Another drug named ribavirin has proved itself effective against virus, but only In vitro.
Yet treatment is limited to supportive care as for Nipah virus encephalitis, mode of transmission can also be from person to person. Proper nursing techniques prevents hospital acquired infections also known as nosocomial transmission.
Preventive methods for the infection against NiV virus
Quite a simple way to prevent the infection is to avoid direct contact with sick pigs and bats in endemic areas and avoid drinking raw date palm sap.
Awareness against the virus can prove to be a helping step for preventing further future outbreaks. Awareness of symptoms and transmission can reinforce standard infection control and can prove to be helpful in avoiding person to person transmission of the deadly virus.
Recently a vaccine has been prepared using hendra G protein. It produces cross protective anti bodies and has been used in Australia to save horses against the hendra virus. This vaccine has proved to be effective for protecting henipavirus infections in humans as well.
Various other pathologies caused by Nipah virus
Most of the other pathologies seen in relation to NiV virus are severe headaches. Problems in swallowing, blurred vision. About a quarter of patients suffer from seizers. The conscious state deteriorates with time, and severe hyper tension develops with a high temperature and fast heart rate.
The very same virus in animals causes porcine respiratory and neurological syndrome which is locally named as mile cough syndrome.