進入2026年初，印度尼帕病毒疫情再度引發國際高度關注，關鍵原因在於疫情出現「地理擴散的新變化」。根據印度官方與國際公共衛生通報，西孟加拉邦近期確認出現尼帕病毒感染病例，這是該地區自2007年以來、時隔19年後再次出現相關疫情。過去尼帕病毒在印度的病例幾乎集中於南部的喀拉拉邦，此次北東部地區重新出現感染個案，被視為疫情風險結構的重要轉折點，也因此引起世界衛生組織（WHO）與印度中央政府的高度警戒。

尼帕病毒之所以被列為全球高度關注的危險病原，與其本身極端的致死特性密切相關。根據歷次疫情的統計資料，不同地區的病死率存在差異，但整體落在40%至75%之間，屬於目前已知人畜共通病毒中致死率最高的類型之一。更令人憂心的是，尼帕病毒並非僅限於動物傳人，而是具備清楚且多次被證實的人傳人能力，尤其在家庭照護與醫療環境中，曾造成群聚感染。

在傳染源方面，尼帕病毒的天然宿主被確認為狐蝠科果蝠，這類大型蝙蝠廣泛分布於南亞與東南亞地區。病毒可經由果蝠的尿液、唾液或排泄物污染食物，最典型的案例是未經處理的新鮮水果或生椰棗汁。此外，病毒也能先感染豬等中間宿主，再由動物傳染給人類。除了動物傳人之外，若與患者的體液、分泌物或排泄物有密切接觸，尤其是在未充分防護的情況下，也可能發生人際間的直接傳播，這一特性使尼帕病毒具備區域性甚至跨國擴散的潛在風險。

潛伏期是尼帕病毒防疫上的另一項重大挑戰。一般情況下，潛伏期約為4至14天，但醫學文獻中也曾記錄最長可達45天的案例。如此漫長且不穩定的潛伏期，讓接觸者在無症狀狀態下仍可能跨區甚至跨境移動，增加疫情監測與隔離管理的難度。

在臨床表現上，尼帕病毒初期症狀往往不具高度辨識性，常被誤認為一般流感或腸胃道感染。患者初期多出現發燒、頭痛、全身倦怠、嘔吐與喉嚨痛等症狀，但病程惡化速度極快，部分患者會在短時間內進展為嚴重呼吸道感染，甚至出現急性腦炎。當中樞神經系統受到侵犯時，可能引發抽搐、意識混亂、嗜睡，最終陷入昏迷，死亡風險極高。

就目前醫療現況而言，尼帕病毒仍缺乏已獲核准的特效疫苗或專一性抗病毒藥物。臨床治療主要以支持性療法為主，包括維持呼吸功能、控制腦壓、處理併發症，以及嚴格的隔離與感染控制措施。這也意味著，防疫工作的重心必須放在「早期發現、快速隔離與阻斷傳播鏈」上，而非依賴事後治療。

正因尼帕病毒同時具備高致死率、可人傳人、潛伏期長與缺乏疫苗等特性，世界衛生組織早已將其列為具有潛在大流行風險的優先監測病原之一。此次疫情重新出現在西孟加拉邦，也再次提醒各國公共衛生體系，必須持續關注人畜共通病毒的跨區流動風險，並加強對高風險地區的疾病監測、食品安全管理與醫療人員防護。

總體而言，尼帕病毒疫情並非單一國家的內部問題，而是一項牽動區域安全與全球公共衛生警戒的長期挑戰。隨著人類活動範圍擴大與生態環境變化，這類高危險性病毒的出現頻率與地理分布，仍值得國際社會持續高度關注。

As of early 2026, the re-emergence of the Nipah virus outbreak in India has once again drawn intense international attention, largely because the epidemic has shown a new and concerning shift in its geographic pattern. According to official announcements from Indian authorities and international public health agencies, confirmed Nipah virus cases have recently been detected in West Bengal. This marks the first reported outbreak in the region since 2007, ending a 19-year absence. Historically, Nipah virus cases in India were almost exclusively concentrated in the southern state of Kerala. The reappearance of infections in eastern India is therefore regarded as a significant change in the outbreak’s risk profile and has prompted heightened vigilance from both the World Health Organization (WHO) and India’s central health authorities.

The Nipah virus is classified as one of the world’s most dangerous pathogens primarily due to its extremely high fatality rate. Based on data from previous outbreaks, mortality rates vary by region but generally range from 40% to as high as 75%, placing Nipah among the deadliest known zoonotic viruses. Even more alarming is the fact that the virus is not limited to animal-to-human transmission. Sustained human-to-human transmission has been clearly documented in multiple outbreaks, particularly within households and healthcare settings, where close contact has led to cluster infections.

In terms of its source, fruit bats of the Pteropodidae family have been identified as the virus’s natural reservoir. These large bats are widely distributed across South and Southeast Asia. The virus can spread when food is contaminated by bat urine, saliva, or feces, with unprocessed fruits and fresh date palm sap being among the most commonly implicated sources. In addition, Nipah virus can infect intermediate animal hosts such as pigs, from which it may then be transmitted to humans. Beyond zoonotic transmission, direct human-to-human spread can occur through close contact with an infected person’s bodily fluids or secretions, particularly in the absence of adequate protective measures. This characteristic significantly increases the risk of localized outbreaks escalating into regional or even cross-border public health events.

Another major challenge in controlling Nipah virus lies in its incubation period. Under typical circumstances, the incubation period ranges from four to fourteen days. However, medical literature has documented cases with incubation periods extending up to forty-five days. Such a prolonged and unpredictable incubation window allows exposed individuals to remain asymptomatic while traveling across regions or national borders, greatly complicating surveillance, contact tracing, and quarantine efforts.

Clinically, early symptoms of Nipah virus infection are often non-specific and difficult to distinguish from common illnesses, leading to delayed diagnosis. Initial manifestations frequently include fever, headache, general fatigue, vomiting, and sore throat, which may resemble influenza or gastrointestinal infections. However, disease progression can be extremely rapid. In severe cases, patients may quickly develop acute respiratory distress and life-threatening encephalitis. Once the central nervous system is affected, symptoms can escalate to seizures, confusion, drowsiness, and ultimately coma, with a very high risk of death.

At present, there are no approved vaccines or specific antiviral treatments targeting the Nipah virus. Medical management is therefore limited to supportive care, including maintaining respiratory function, controlling intracranial pressure, managing complications, and enforcing strict isolation and infection-control protocols. This reality means that public health strategies must prioritize early detection, rapid isolation of cases, and the interruption of transmission chains, rather than relying on curative treatments.

Because the Nipah virus combines a high fatality rate, the ability to spread between humans, a long incubation period, and the absence of effective vaccines or targeted therapies, the WHO has designated it as a priority pathogen with pandemic potential. The renewed outbreak in West Bengal serves as a stark reminder to public health systems worldwide of the need to remain alert to the cross-regional movement of zoonotic diseases and to strengthen disease surveillance, food safety oversight, and protective measures for healthcare workers in high-risk areas.

Overall, the Nipah virus outbreak is not merely a domestic issue for any single country but a long-term challenge with implications for regional stability and global public health security. As human activity continues to expand and ecological conditions change, the frequency and geographic spread of high-risk zoonotic viruses like Nipah are likely to remain a critical concern for the international community.