A groundbreaking study published in Emerging Infectious Diseases has revealed the presence of Pteropine orthoreovirus (PRV), a bat-borne virus previously undetected in humans with severe illness, among Bangladeshi patients initially suspected of Nipah virus infection. This discovery, led by researchers from Columbia University's Mailman School of Public Health in collaboration with Bangladeshi health authorities, analyzed archived throat swab samples from five patients exhibiting acute symptoms such as high fever, intense headaches, persistent vomiting, profound fatigue, and neurological complications like confusion and seizures. These individuals had recently consumed raw date-palm sap—a traditional winter delicacy in the region—known as a primary vector for bat saliva and urine contamination.

Standard Nipah diagnostic tests, which rely on PCR assays targeting Nipah-specific genetic sequences, returned negative results for all five cases. Undeterred, the research team employed viral capture sequencing (VCS), an advanced metagenomic technique that unbiasedly scans for a broad spectrum of viral nucleic acids. This approach not only identified PRV RNA in the samples but also enabled the successful cultivation of live virus in cell culture, confirming viable, replicating infection.

PRV belongs to the Reoviridae family, specifically the genus Orthoreovirus, with pteropine strains historically associated with fruit bats (Pteropodidae family) in Southeast Asia and Australia. Prior detections in humans, such as in Indonesia and China, linked PRV to mild respiratory illnesses or isolated cases, but this Bangladeshi cohort marks the first evidence of severe manifestations, including pneumonia-like respiratory distress and encephalitis-like brain involvement.

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Dr. Nischay Mishra, the study's lead author and an expert in viral discovery at Columbia, emphasized the implications: "Our results demonstrate that the zoonotic risks tied to raw date-palm sap extend far beyond Nipah virus. PRV's ability to mimic Nipah symptoms could lead to misdiagnosis and underreporting if surveillance remains narrowly focused." The virus's genetic analysis revealed close relatedness to bat-derived strains, suggesting direct spillover from pteropus bats (flying foxes), which roost near date-palm groves and contaminate sap through licking or droppings during the January-to-April harvesting season.

Nipah virus (NiV), a paramyxovirus with a case fatality rate of 40-75% per World Health Organization (WHO) estimates, has caused over 300 human cases in Bangladesh since 2001, primarily through date-palm sap exposure. Outbreaks peak in winter, with secondary human-to-human transmission amplifying spread in healthcare settings. Neighboring India reports sporadic incursions, including deadly clusters in Kerala (2018, 17 deaths) and West Bengal (2023), prompting states like Kerala to implement rapid contact-tracing protocols, community quarantines, and sap-boiling mandates—strategies that contained outbreaks sans vaccine.

PRV's emergence complicates this landscape. Bats in South Asia harbor diverse reoviruses, with serological surveys indicating human exposure rates up to 20% in high-risk communities. Unlike Nipah's person-to-person potential, PRV transmission appears zoonotic-only thus far, but its respiratory tropism raises pandemic concerns akin to SARS-CoV-2. Nations like India, Nepal, Myanmar, and Bhutan share overlapping bat habitats and cultural practices (e.g., toddy palm tapping), amplifying spillover risks amid climate-driven bat migrations and deforestation.

Experts advocate metagenomic surveillance platforms, like VCS or nanopore sequencing, to detect "orphan" viruses preemptively. India's Integrated Disease Surveillance Programme (IDSP) could integrate these, building on Kerala's model of real-time genomic labs. The WHO urges low-to-moderate risk assessments for Nipah but now flags PRV for monitoring.

Key Precautions for At-Risk Populations:

• Refrain from raw date-palm sap; boil or pasteurize to 65°C for 30 minutes to neutralize enveloped and non-enveloped viruses.

• Install bamboo skirts on sap-collecting pots to block bat access, a proven 80-90% effective intervention per field trials.

• Seek immediate care for fever >38°C, headache, vomiting, dyspnea, or altered mentation post-bat exposure; request broad viral panels.

• Advocate for expanded funding in national health budgets for one-health initiatives bridging human, animal, and environmental monitoring.

This PRV revelation signals that bat-human interfaces harbor a viral "dark matter" demanding vigilant, multi-pathogen preparedness. As South Asia grapples with Nipah's shadow, ignoring such hidden threats invites catastrophe.

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