Flu

Nipah Virus Infection | All you need to know

infection

: The incidence of acute encephalitis that occurred in Malaysia in March 1999 has been elucidated as infection of pigs with a novel paramyxovirus, (nipa ), and encephalitis in humans. The Malaysian government slaughtered the pig that became the source of infection and blocked the infection route to humans. However, in 2004, cases of human infection were found in Bangladesh (see Appendix 1). Nipah infection was an outbreak as an emerging infection, but the importance of surveillance of daily diseases, the response when unknown ones appear among them, measures for severe infections / new infections at national level The importance of international cooperation for emerging infectious diseases has been reaffirmed.
In Japan, there has been no direct damage ever since that time, but according to the Infectious Diseases Act revised in November 2003, this disease was designated as a quaternary infection.

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Epidemiology In
1997, there was an epidemic of acute encephalitis among swine farm workers in Kint, Northern Perak State, Malaysia, with one death. The area is a resident area of ​​Japanese encephalitis (JE), and at that time it was thought that this epidemic might be caused by the JE virus. The next day, in September 1998, another case of acute encephalitis occurred among pig producers in Ipoh, the capital of the province, and a few cases continued until February 1999. From December 1998 to January 1999, similar patients were found around Sikamat City in Negri Sembilan Province in the south near the capital city Kuala Lumpur. The third cluster is the largest, and a few cases occurred in December 1998 in Bukit Pelandok City, Negri Sembilan Province, and the number of patients increased sharply in February and March 1999, with dozens of people each week. It increased, half of which was death.

Nipah Virus Infection
Infection

All were initially considered JE, and measures were taken such as control of mosquitoes and mass vaccination of JE vaccine, but most of the patients are adult males, and they are involved in slaughter of pigs in pig farms. JE has a different encephalitis condition than JE because of being a worker, having a patient outbreak from JE vaccine-vaccinated people, and having a case of respiratory and nervous system symptoms in pigs in a pig farm. Investigation was advanced as an epidemic.
During the course of the outbreak, Nipah virus was identified as a pathogen. There were 265 patients enrolled as acute encephalitis between September 1998 and March 1999, of which 105 were fatal. 155/265 people were infected with Nipa virus, 37/265 people were infected with Nipah / JE, and 11/265 people were confirmed with JE. Of the deaths, 55/105 were infected with Nipah, 21/105 were infected with Nipah / JE, and 4/105 were infected with JE.

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93% of people with encephalitis are involved in pig farms, 41.9% are workers, 38.5% are managers, and even if they are not directly related to them, they have experience working in a pig farm, or He was very close to the pig farm. The ages were 10% to 19% at 6.4%, and those below 10 years were only 12%, most of them at 20 years of age and 82.6% male.
Malaysia is a multi-ethnic nation consisting of Malay, Chinese and Indian people. Chinese residents account for only about 5% of the total, but 70.6% of the patients in this case are Chinese, and 11.3% are Indian, 11.1% are foreign workers, and 1.1% are Malay. The The majority of pig producers in Malaysia are Chinese.

The above age, sex, occupation, race, etc. can not be explained by the JE epidemic, and this epidemiological trend becomes clear from the time of the third cluster occurrence and strongly suggests the possibility of non-JE It became.

Pathogen

 At Malaya University, we tried to isolate viruses in 2 cases of cerebrospinal fluid obtained from 3 cases of death in the early stage of the third cluster. Was confirmed. It was morphologically paramyxovirus-like but unidentifiable. All known viruses and JE viruses were negative. This virus is similar to Hendra virus (see Appendix 2: originally called equine morbilivirus), a new paramyxovirus found in Australia in 1994 by the US CDC (Centers for Disease Control and Prevention). It turned out to be a virus.
Fig. Electron micrograph of Nipah virus (provided by Koichi Morita, Institute of Tropical Medicine, Nagasaki University)

However, this virus was found to have 21% mutation at the gene level and 11% at the amino acid level, and was considered to be a related but independent new paramyxovirus. The virus, originally called Hendra virus-like virus, was newly named the Nipah virus (Nipah virus) after the name of the village and the river from which the virus was isolated (Figure).
The route of infection is considered to be in intimate contact with the secretions and urine etc of infected pigs. At the beginning of the epidemic, health care workers treated patients as JE, and they did medical care, general examination, dissection, virus testing etc. without paying special attention to biohazards. Since then no people infected with the virus have been found. Therefore, the possibility of human-to-human transmission was considered to be extremely low.
The natural host of Nipah virus is bats. In Malaysia, as the pig farming industry flourishes, jungle and the like are cut open and large-scale management is realized, and as a result, it is considered that a pig encounters an unknown virus and the infection is transmitted to humans through the pig.
Among patients with acute encephalitis in northern Malay City in 1997, some have demonstrated IgG antibodies against Nipa virus, and it is presumed that Nipa virus encephalitis had already occurred in 1997.

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Clinical symptoms / signs
The main clinical symptoms are acute cerebral inflammation such as fever, headache, dizziness, vomiting, etc., which occur suddenly, and there is nothing specific. In the case of 94 confirmed cases, 55% of patients showed impaired consciousness, brainstem dysfunction etc., and myoclonus, hypotonia, hypertension, polypnea etc. appeared. Some cerebrospinal fluid abnormalities are seen in 75%. 53% complete recovery, 32% fatality rate, 14% of those who left a sequelae such as neurological disorder, it can be said that it is a serious disease with extremely poor prognosis. In addition, doll’s eye finding (doll’s eye finding), high blood pressure, tachycardia, etc. were signs of poor prognosis.
Three patients who have had a neurological disorder have a relapse of their symptoms 3 to 39 days after the initial symptom. In addition, although the proportion is not clear, the existence of a latently infected person has also been pointed out.
There is nothing specific in general clinical examination. Common histologic findings included vasculitis and endothelial cell injury in the central nervous system, including necrosis of blood vessel walls, thrombosis, and infiltration of inflammatory cells such as lymphocytes and neutrophils. This vascular disorder was also seen in the lung, heart, kidney and so on.
The clinical symptoms of the pig that became the source of human infection are primarily respiratory symptoms, with moderate to severe cough, increased airway secretions, dyspnea, or sometimes convulsions and other neurological symptoms. Nipavirus morbidity in pigs is high but its mortality is low unlike in humans. More than 90% of swine were reported to be antibody positive in a swine farm. In the endemic areas, it was also reported that dogs (more than 50%), cats (1/23), horses (2/47) and bats (15/99) were positive for Nipa virus antibodies.

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Pathogen Diagnosis

Pathogen diagnosis uses spinal fluid, urine, airway secretion fluid, and the like as materials, and isolates viruses in tissue culture using Vero cells and the like. Measurement of serum IgM antibodies, viral gene detection methods using RT-PCR, etc. have also been established

Treatment / Prevention

The treatment is based on the treatment of acute encephalitis, but there are reports that ribavirin was effective. There is no vaccine protection method.

Appendix 1: Multiple outbreaks of Nipa virus infection have been identified in Bangladesh in 2004. Mortality rates were 60-74% higher than those reported at 40% in Malaysia. In Malaysia, the infection was through pigs, but in Bangladesh it is said that the infection was from fruits contaminated with virus-bearing bats. It is also speculated that human-to-human transmission may have occurred.

Appendix 2: Hendra virus: RNA virus classified as paramyxovirus. In 1994, the race horse pneumonia infects three humans in Australia, and the death of two has made it clear for the first time. One was a respiratory infection and one was a central nervous infection. The natural host is a large bat (fruit bat), which is transmitted from bats to horses, and horse urine is considered to be a source of infection for humans. Although there have been no reports of subsequent human transmission, Hendra virus has been confirmed in Papua New Guinea bats.

What are treatments for a Nipah virus infection?

According to the U.S. Centers for Disease Control and Prevention (CDC), supportive care is the only current treatment for this viral infection. There is no vaccine specifically available to protect humans. However, some researchers suggest that the antiviral drug ribavirin may be useful, but there is little or no data to support this. A human monoclonal antibody that targets the G glycoprotein of NiV has shown benefit in a ferret animal model of this disease, but researchers have not studied the effects of the antibody in humans.

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What is Nipah virus infection (NiV)?

Nipah virus infection is a zoonosis transferred by contact with an NiV-infected animal or person or their secretions that has a high fatality rate in infected humans.

What causes a Nipah virus infection?

NiV.

What are signs and symptoms of a Nipah virus infection?

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The signs and symptoms of NiV infection begin with

Encephalitis follows and those infected may exhibit drowsiness, disorientation, mental confusion, altered consciousness, and seizures that can progress, within 24-48 hours, to coma and eventually death.

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