The Nipah virus has once again become an international focus following the detection of new cases in the Indian state of West Bengal. Indian authorities and international health organizations have activated surveillance and control protocols , while in Europe, and especially in Spain, experts insist that the current risk to the population is very low , although the situation is being closely monitored.
Although alarmist headlines have spoken of a “risk of a global epidemic” and compared Nipah to the COVID-19 pandemic, the available data points to a much more limited scenario: few confirmed cases, limited transmission, and a rapid health response in the affected area. This does not diminish the seriousness of the virus, which has a high fatality rate and lacks a specific treatment, but it does help to put its real impact for countries like Spain into context.
What is the Nipah virus and how is it transmitted?
Nipah virus is an emerging zoonotic pathogen that was first identified in the late 1990s during an outbreak in Malaysia and Singapore . It belongs to the genus Henipavirus , within the family Paramyxoviridae , and is classified by the WHO as a Group 4 biohazard , the highest level of risk, due to its high mortality rate and the lack of approved therapies or vaccines.
Its natural reservoir is fruit bats of the genus Pteropus . These animals can shed the virus through saliva, urine, or feces, contaminating fruit, date palm sap, or other foods . In some outbreaks, especially the one in Malaysia, pigs acted as intermediate hosts, amplifying the infection and facilitating its transmission to humans.
Transmission to humans can occur through direct contact with secretions or excretions from infected animals , by consuming contaminated products—such as raw date palm sap in Bangladesh—or through respiratory droplets and bodily fluids in close-contact settings. Person-to-person transmission has been documented in several instances , particularly among close family members and healthcare workers treating patients.
Since its identification, an estimated 750 human cases have been recorded in total, with outbreaks documented only in Bangladesh, India, Malaysia, and Singapore . Although serological studies suggest a possible presence of the virus or related viruses in other Southeast Asian and African countries, clinical cases have been concentrated in a very limited geographical area.
Clinical picture and symptoms of Nipah
Nipah infection can present in a wide variety of ways, from asymptomatic infections to extremely severe cases. The case fatality rate reported in outbreaks varies between approximately 40% and 75% , according to data from the WHO and various affected countries.
In many patients, the illness begins with flu-like symptoms : fever, headache, general malaise, and muscle aches . These initial signs may be accompanied by a sore throat, vomiting , and intense fatigue, making it difficult to distinguish from other respiratory infections in the early stages.
In a significant percentage of cases, the infection progresses to an acute respiratory illness with severe cough and difficulty breathing, or to viral encephalitis , that is, inflammation of the brain. This neurological involvement can manifest as disorientation, drowsiness, confusion , or altered mental status, and in the most severe cases can lead to coma within 24-48 hours.
Clinical series indicate that between 8% and 15% of patients may present with subclinical forms , with very mild symptoms or even no obvious manifestations. Relapses and late-onset encephalitis have also been described in people who had apparently recovered from a first episode.
The incubation period —the time from exposure to the virus until the onset of symptoms—is usually between 4 and 18 days , although intervals of up to two months have been documented . This relatively wide range necessitates continued monitoring of contacts for several weeks to rule out new secondary cases.
What is happening in West Bengal (India)
The outbreak that has triggered renewed alerts occurred in West Bengal , a densely populated state in eastern India whose capital is Kolkata. The Indian Ministry of Health reported two suspected cases of Nipah virus disease on January 12, 2026 , which were confirmed on January 14 after laboratory testing. These are the first cases detected in the region since 2007.
The first confirmed patients were two nurses who worked at a private clinic in Barasat , in the Kolkata metropolitan area, about 24 kilometers from the city. Both presented with severe symptoms. One of them has shown progressive improvement and was able to be extubated on January 16; the other remains in a coma and continues in critical condition, with no significant changes.
Preliminary investigations, compiled in the WHO Epidemiological Bulletin and reports from India's National Centre for Disease Control (NCDC) , indicate that the two healthcare workers may have been exposed to the virus during a work visit to the Purba Bardhaman district . There, they treated a person with severe respiratory distress who died from causes not yet confirmed as Nipah, but who could be the index case of the outbreak.
Following the confirmation of the positive cases, several suspected cases were identified among healthcare staff who had been in close contact with the nurses. A doctor and another nurse developed fever and cough and were hospitalized as a precaution, although initial tests for Nipah were negative . Both remain under observation as high- and low-risk contacts, respectively , pending repeat testing.
Meanwhile, another healthcare worker with compatible symptoms was admitted to the infectious diseases hospital in Beleghata . These types of preventative admissions, which some media outlets have interpreted as new infections, are in accordance with the quarantine and isolation protocols established for this virus.
Confirmed cases, contacts, and misinformation
The number of those affected has caused some confusion in the media. While some headlines have reported five confirmed cases and an out-of-control situation, Indian authorities have stressed that, according to available official data, there are only two laboratory-confirmed cases in West Bengal, both corresponding to the two nurses initially identified.
State government representatives and experts consulted by the local press have denied the figure of five infections, clarifying that the rest are suspected cases or contacts under observation who have tested negative in initial tests or are still awaiting confirmation. Some of these patients have already been discharged after the infection was ruled out.
In total, authorities have traced and monitored approximately 190-200 people who had some form of contact with the nurses or the potential index case. According to data from the NCDC and the Government of India, 196 contacts have been identified and actively monitored , undergoing screening, diagnostic testing, and home quarantine based on their level of risk.
The Indian government has indicated that, to date, no new cases have been detected among these contacts. All those traced remain asymptomatic and have tested negative, although monitoring continues because the incubation period can be up to 45 days , and some experts recommend extending follow-up for up to three months before declaring the outbreak over.
This discrepancy between the epidemiological reality and some sensationalist headlines has led the authorities to publish specific statements to curb the spread of speculative and incorrect figures and avoid unjustified alarms, both inside and outside India.
Health response in India and neighboring countries
In response to the reemergence of Nipah, India's Ministry of Health has issued a national alert urging all states to strengthen epidemiological surveillance, accelerate the detection of suspected cases, and implement stricter preventative measures in hospitals and health centers. The National Center for Disease Control and Prevention (NCDC) has activated its emergency protocols through a technical circular detailing the virus's characteristics and guidelines for action.
In the state of West Bengal, specific patient isolation circuits have been established , along with enhanced use of personal protective equipment for healthcare workers and cleaning and disinfection protocols in areas where suspected cases are treated. Surveillance has been intensified in both public and private hospitals, with clear instructions to immediately report any compatible symptoms.
Furthermore, research is being conducted on wildlife to identify potential reservoirs and transmission chains. At Alipore Zoo in Kolkata, samples have been taken from bats for RT-PCR analysis , following strict biosafety protocols, to confirm whether the virus is circulating in these populations.
The impact of the outbreak has transcended India's borders. Thailand , which receives a daily influx of travelers from Kolkata and other parts of India, has implemented temperature checks and targeted screenings at Suvarnabhumi, Don Mueang, and Phuket airports to detect travelers with respiratory symptoms or fever who have recently been in the affected areas.
Thai authorities have advised people who have visited West Bengal in the past three weeks to go immediately to a health center if they develop fever, headache, muscle aches, cough, difficulty breathing, drowsiness, confusion or seizures, and to always report their travel history.
Global background of Nipah
The Nipah virus is not new to Southeast Asian health systems. Since the first major outbreak detected in 1998-1999 in Malaysia and Singapore , linked to pig farms, recurring outbreaks have been reported in countries such as Bangladesh and India . In Malaysia, the crisis led to the culling of more than one million pigs and caused hundreds of cases of encephalitis and more than one hundred deaths , with a huge economic impact.
In Bangladesh , outbreaks have occurred almost every year since 2001, with a particularly high fatality rate. Many of these outbreaks are linked to the consumption of raw date palm sap contaminated with secretions from fruit bats, a pattern that illustrates how certain traditional practices can facilitate the virus's transmission to humans.
In India, in addition to the current outbreak in West Bengal, the state of Kerala has experienced several outbreaks in recent years. The most serious occurred in 2018 , with at least 17 deaths . In September 2023, a new outbreak in the same region led to the temporary closure of schools , the confinement of more than a thousand people, and the mobilization of extraordinary resources to contain the infection.
Other countries have also reported isolated outbreaks. In the Philippines , a 2014 outbreak was linked to the consumption of infected horse meat and caused at least 17 deaths. Beyond clinical cases, several studies have detected antibodies against henipavirus in bats in Africa and other regions, suggesting a wider circulation of related viruses, although without any concrete evidence of human outbreaks to date.
The World Health Organization includes Nipah among the pathogens with the greatest epidemic potential , not so much because of its ease of transmission—which is relatively low compared to other respiratory viruses—but because of the combination of high mortality , lack of specific treatment, and the possibility that ecological or human behavior changes could open the door to more widespread outbreaks.
Risk for Spain and the rest of Europe
In Europe, the situation is being analyzed carefully, but without alarmism. The Spanish Ministry of Health , through the Center for Coordination of Health Alerts and Emergencies (CCAES) , and organizations such as the European Centre for Disease Prevention and Control (ECDC) , agree that the current risk for Spain and the rest of Europe is very low.
Official reports highlight several key factors. First, there is no evidence of either locally acquired or imported cases of Nipah virus in Spain or the European Union. To date, no human infections with this pathogen have been diagnosed, nor has the virus been detected in domestic or wild animals in Europe.
Secondly, the absence of the main reservoir in our environment makes it extremely unlikely that the virus can become established in a sustained manner. No populations of the fruit bat species of the genus Pteropus , which act as a reservoir in Asia, have been described in Spain. The only known instance of Rousettus aegyptiacus being identified in the Balearic Islands is in the Balearic Islands. This megabat species has been identified as a possible reservoir for other henipaviruses, but it has been considered practically extinct in Spain since 2005, and neither the Nipah virus nor antibodies against it have been detected in this species.
Furthermore, neither Nipah nor compatible antibodies have been detected in mammals in Spain or the rest of Europe. The available data allow us to conclude that, at this time, neither the virus nor its natural reservoir are established in our environment, which minimizes the probability of autochthonous cases appearing.
The Spanish Society of Preventive Medicine, Public Health and Healthcare Management points out, however, that a very low risk does not equate to zero risk , and that it is necessary to maintain the capacity to respond to emerging infections. To this end, it is considered essential to maintain and strengthen epidemiological surveillance , laboratory systems, and rapid response protocols for any suspected case.
The Spanish Society of Infectious Diseases and Clinical Microbiology also insists that the probability of the virus reaching Spain and causing a pandemic is low , partly because Nipah's transmissibility is relatively limited. Even so, it emphasizes that the Spanish healthcare system, universal and well-structured , has gained experience managing recent major health crises and has considerable scientific and clinical capacity to deal with any imported cases.
Official risk assessment in Spain
The CCAES emphasizes that Nipah virus disease is listed in the World Organisation for Animal Health's Terrestrial Animal Health Code as a notifiable disease , which means that any suspicion in animals must be reported to the competent authorities immediately.
In our country, risk analyses indicate that no natural reservoirs of the virus have been identified in either native fauna or domestic animals. None of the bats in which the virus or antibodies have been detected in other regions of the world—such as P. hypomelanus, P. vampyrus, P. giganteus, P. lylei, Cynopterus brachyotis, Eonycteris spelaea, Scotophilus kuhlii, or Hipposideros larvatus —are part of the established fauna in Spain.
Consequently, health authorities consider the current probability of locally acquired cases in the Spanish population to be practically nil . The risk is theoretically limited to imported cases linked to travel from endemic areas, a scenario considered unlikely but for which detection and management protocols exist within the health services.
Even so, the Ministry of Health stresses the importance of maintaining close coordination between human and animal surveillance systems, continuing education of healthcare professionals in emerging diseases, and strengthening infection control measures in hospital settings , especially when treating patients from regions with known Nipah circulation.
In case of suspicion in Spain, samples would be sent to reference laboratories with high-level biosafety capabilities, and the isolation, contact tracing and international notification circuits set out in the International Health Regulations would be activated.
Challenges in surveillance, diagnosis and vaccines
Beyond the specific outbreak in West Bengal, several international experts have pointed out that Nipah remains an outstanding challenge for preparedness against future health emergencies. A recent commentary published in a high-impact scientific journal reviews the gaps that persist in surveillance, diagnosis, and vaccine development against this virus.
The text, prepared following an international meeting with specialists from more than 25 institutions , highlights that while laboratory tests exist to detect Nipah, many are based on assays developed locally at reference centers and are neither standardized nor easily scalable . This hinders their use in unexpected outbreaks or in settings with limited technical resources.
Therefore, the development of rapid, sensitive, and field-usable diagnostic tests is a priority , especially in rural areas of endemic countries , where the first cases often appear and where access to sophisticated laboratories is limited. Early diagnosis is key to activating isolation, contact tracing, and quarantine measures in a timely manner.
In the field of clinical research, experts emphasize that neurological involvement —encephalitis—is a leading cause of mortality and long-term sequelae . However, many preclinical studies have focused primarily on respiratory disease, leaving important areas to explore regarding how to prevent or treat neurological damage associated with the infection.
Regarding vaccines, it is acknowledged that significant progress has been made in recent years. At least three vaccine candidates are in different phases of development, some undergoing human clinical trials (phases I and II) and others showing promising results in animal models, including primates. Even so, there is still no vaccine authorized for general use against Nipah.
The scientific document concludes that, despite progress, sustained effort and greater investment are needed to address gaps in epidemiology, diagnostics, immunology, and the development of countermeasures . This preparedness would not only benefit currently affected countries but would also strengthen the global capacity to respond to any future spread of the virus.
Nipah in the context of other infectious threats
Experts point out that Nipah is part of a broader group of emerging diseases under constant surveillance. These include avian influenza H5N1 , MERS-CoV , and various arboviruses such as dengue, chikungunya, and Zika, which affect different regions of the world with very different transmission patterns and levels of risk.
In this context, the WHO warns that factors such as urban sprawl, environmental degradation, and the encroachment on natural habitats increase contact between humans and wildlife, raising the likelihood of viruses of animal origin jumping to the human population. Fruit bats , in particular, have been identified as reservoirs for multiple pathogens with epidemic potential.
Virology experts indicate that Nipah is currently a bat virus that causes occasional zoonotic outbreaks , with no signs of sustained transmission in the human community. The highest-risk groups are close relatives of index cases and healthcare workers treating them, especially in settings with fewer resources for systematically implementing protective measures.
Although Nipah has a very high fatality rate, its transmissibility is significantly lower than that of other respiratory viruses, and it is estimated to be much less transmissible than SARS-CoV-2 . This explains why, despite annual outbreaks in certain areas, widespread transmission beyond local hotspots has not been observed .
From a global health perspective, the main challenge is ensuring that countries where the virus is endemic have robust surveillance systems, trained laboratories, and clear protocols for rapid response. This early response capability is one of the best guarantees for reducing the risk of local outbreaks escalating into larger problems.
The current Nipah virus situation combines, on the one hand, limited but very serious outbreaks in certain areas of Southeast Asia and, on the other, a very low probability of direct impact on countries like Spain, which do not have a natural reservoir and have not registered any cases. Maintaining vigilance, transparency in information, and international coordination allows us to address this threat proportionately, avoiding alarmism but also avoiding complacency.