What You Need to Know About Nipah Virus
How Is Nipah Virus Transmitted?
Fruit bats, also known as flying foxes, are the natural reservoir hosts of NiV. The virus is present in bat urine, feces and saliva. Fruit trees can attract bats from surrounding habitats. Bats inhabiting the fruit trees lead to . Since NiV can survive in substances that are rich in sugar, such as in fruit pulp or date palm sap, consumption of contaminated fruit can lead to infection. In the 1998 outbreak in Malaysia, fruits that were partially consumed by bats infected with the virus were subsequently ingested by pigs. Then workers and pig farmers became infected after close contact with ill pigs.
Past and Present Nipah Outbreaks
Several countries have reported NiV outbreaks, including Bangladesh, India, Philippines, Malaysia and Singapore. In India, outbreaks have been reported in the states of West Bengal (2001 and 2007) and Kerala (2018 and 2021).
In involved 17 cases between March and May. This outbreak was linked back to exposure to infected horses and contact with contaminated body fluids from sick horses during slaughtering and/or consumption of contaminated or undercooked horse meat. Secondary human-to-human cases likely occurred due to lack of appropriate preventative measures and infection control practices in the homes of infected individuals and in healthcare facilities.
A few years later, a and involved 13 cases with 11 deaths. Evidence suggests that the likely origin of this outbreak was exposure to bat secretions from forest trekking, eating fruits bitten by bats or .
In Bangladesh, human consumption of raw date palm sap contaminated with NiV from bat excretions is a major risk factor for acquiring NiV infection and has led to . These outbreaks often follow a seasonal pattern in the winter and spring seasons (November to April), which coincides with date palm sap harvest.
According to a March 2023 report from the (WHO) and the Bangladesh Institute of Epidemiology, Disease Control and Research (IEDCR), the current 2023 outbreak has accumulated 14 cases and claimed 10 lives. Cases have been reported across seven districts in Bangladesh thus far, although, historically, cases have been reported in numerous districts across the country.
Pathogenesis and Diagnosis
NiV is a single-stranded, non-segmented, enveloped RNA virus. The RNA genome consists of 6 genes: nucleocapsid (N), phosphoprotein (P), matrix (M), fusion glycoprotein (F), attachment glycoprotein (G) and long polymerase (L). The F and G proteins are responsible for cellular attachment and entry into the host cell. The virus infects respiratory epithelial and pulmonary endothelial cells, and eventually enters the bloodstream, where it infects organs, including the spleen, kidney and brain. Viral entry into the central nervous system damages the blood-brain barrier, leading to neurological symptoms. include fever, headaches, myalgia, respiratory illness, seizures, blurred vision and encephalitis.
NiV symptoms typically appear in 4-14 days following exposure to the virus. Encephalitis (brain swelling) may follow early symptoms, leading to drowsiness, disorientation and mental confusion, which can rapidly progress to coma within 24-48 hours. Mortality occurs in 40-75%. Long-term side effects in survivors of NiV infection include persistent convulsions and personality changes. Interestingly, dormant or latent infections, leading to symptoms or death, have also been reported months and even years after exposure.
Diagnosis of NiV infection is possible during illness or after recovery with a variety of medical laboratory tests. Laboratory testing in early-stage infection can be performed with real-time polymerase chain reaction (RT-PCR) from throat and nasal swabs, cerebrospinal fluid, urine and blood. At the end of illness, and after recovery, indirect testing for antibodies against NiV can be performed using an enzyme-linked immunosorbent assay (ELISA).
due to the non-specific early symptoms of the illness noted prior. One consideration should be for individuals with symptoms consistent with NiV infection (e.g., fever, headache, cough, sore throat and other respiratory difficulty) who have been in areas where Nipah virus is more common, such as Bangladesh or India—particularly if they have a known exposure. Early detection and diagnosis increase survival among infected individuals and assist with prevention of transmission and outbreak management.
Treatment and Vaccine Candidates
Currently, there are no licensed treatments for NiV. Individuals with NiV infections are limited to supportive care, including treatment of symptoms. Immunotherapeutic treatments (monoclonal antibody therapies) are currently under development and evaluation for treatment of NiV infections. clinical trials and has been administered on a . In addition, the has been effective in nonhuman primates when given as post-exposure prophylaxis. efficacy for NiV is unclear but was used to treat a small number of patients in the initial Malaysian NiV outbreak.
Currently, there are , though research to develop a NiV vaccine is ongoing. In July of 2022, the National Institutes of Health (NIH) reported for an investigational Nipah vaccine based on a messenger RNA (mRNA) platform developed by Moderna, Inc., Cambridge, Massachusetts. Results of this trial will be expected after the trial is completed; none are yet available.
In December 2022, a Lancet publication reported that a VSV-EBOV vaccine expressing NiV glycoprotein G (VSV-NiVG), respectively, in the African green monkey model. This was a promising step in the pursuit of a vaccine that confers broad protection against NiV.
One Health Approach
Identifying how new viruses emerge in naïve populations and pinpointing source identification is important to understand the epidemiology of any disease; however, this is extremely challenging. To understand NiV, it is important to identify and document between species and to characterize how bats move over trans-natural boundaries (border between two or more countries or areas and affecting both or all areas, including water like rivers, etc). NiV has certainly shown that it can move beyond one host species and infect others— including humans. Nipah research therefore requires a "," in which multiple sectors coordinate and work together to achieve better public health outcomes. It is imperative that the global public health, research and healthcare community work together in an interdisciplinary effort at all levels and across political and geospatial lines to prevent further Nipah virus transmission.
With climate change, a growing global population and increased interactions between humans and wildlife, the threat of epidemics of infectious diseases is ever-growing. In this next article, learn about Marburg, another zoonotic disease for which bats are a natural reservoir.
