On behalf of TeamHealth’s Emerging Infectious Disease Task Force
This year marks the third outbreak of Nipah virus in the Indo-Bangladesh region. Nipah is a dangerous and often lethal viral disease. Most clinicians in the United States have little to no experience with this viral disease. Because of this, TeamHealth’s Emerging Infectious Disease Task Force (EIDT) thought it was appropriate to produce this short post on the topic of the Nipah virus.
What is Nipah Virus?
The Nipah virus is an encapsulated RNA virus in the family Paramyxoviridae. The name given to the virus was “Nipah” after the nearby river and village in Malaysia where the first outbreak occurred. Nipah viral infections are associated mainly with Pteropus fruit bats common throughout Asia.
Viruses like Nipah can infect a variety of mammals, many of which are domestically cultivated and have close human contact.
Thus far, there has been no evidence of aerosol transmission of the virus.
Nipah Virus Emergence and Status
In 1999, Malaysia and Singapore reported an unusual series of encephalitis cases, associated with agricultural workers. Both the pigs and the human workers developed a form of rapidly progressive encephalitis often accompanied by severe pulmonary symptoms.
The encephalitis cases also demonstrated a high case fatality rate (CFR). In the first outbreak, out of 250 farmworkers contracting the disease, there were 100 deaths (CFR = 40%).
Two Kinds of Outbreaks for Nipah
Almost all outbreaks of Nipah virus are located within the Indo-Bangladesh region. These outbreaks demonstrate high levels of human to human transmission. Most outbreaks outside of this region are usually associated with animal to human transmission.
Since initial reports, annual cases have typically ranged from zero to 67. The outbreak in January 2023 was focused in Kerala, India and had a substantial impact. There were over 300 cases of Nipah virus encephalitis reported and over 100 fatalities.
Another concern is a very high secondary attack rate during subsequent outbreaks. In 2001, a single index case admitted to a private hospital resulted in an estimated 23 hospital staff and eight visitors becoming secondarily infected.
Signs and Symptoms
The incubation period of Nipah virus infection is from 4-14 days post exposure. Patients typically present with fever and headache.
Typical symptoms on initial presentation for Nipah viral disease include fever and headache.
Long-term side effects in survivors of Nipah virus infection include mostly persistent seizure disorders and personality changes. Nipah viral infections or exposures can lead to a reemergence of symptoms and occasionally fatalities.
Diagnosis and Treatment of Nipah Viral Infection
Nipah viral infections can be diagnosed during the acute illness or after recovery. In the acute phase, diagnosis can be made through association with the constellation of symptoms and the use of real-time polymerase chain reaction studies (RT-PCR).
Early diagnosis of Nipah viral infection can be difficult due to the nonspecific nature of early symptoms. Early diagnosis is critical for managing encephalitis and cerebral edema and can help prevent transmission of the disease.
Currently, there are no approved or licensed treatments available for Nipah infection.
Immunotherapy for Nipah Viral Infections
Although no vaccine exists for Nipah virus, immunotherapy with monoclonal antibodies is available in some settings. One monoclonal antibody treatment (m102.4) has completed phase 1 trials and is currently undergoing phase 2 trials.
In addition, the antiviral remdesivir has been studied in nonhuman primates when given as post-exposure prophylaxis and in early phase infection. However, it is not currently approved for this therapy.
Finally, ribavirin was used to treat a small number of patients during the initial Malaysian Nipah virus outbreak, but its efficacy in humans remains unclear.
The Nipah virus represents another emerging viral disease of high transmission and pathogenic potential. This suggests a potential risk for pandemic disease and the need for Nipah and similar diseases to continue to be studied and monitored.