In November 2025, Europe’s largest pig producing country, Spain, discovered the ASF virus in its wild boar population. Research lab IRTA-CReSA, located close to Barcelona, found itself in the middle of that all. While playing a pivotal role in analysing blood and carcasses on the one hand, it became scrutinised on the other: what if the virus had escaped from that same lab? Three scientists look back to months of uncertainty.
“2025 has been one sanitary crisis,” says Professor Natàlia Majó Masferrer, standing in front of the IRTA-CReSA building, where some construction work is going on. “It was one species after another,” responds Professor Joaquim Segalés Coma, referring to the lumpy skin disease, avian influenza and ASF that emerged in Spain last year. “It is super stressful,” adds Dr Carles Vilalta Sans, “dealing with all those diseases on top of your normal work.”
Sense of relief about ASF situation
It is late February 2026 and although the presence of ASF in Spain is far from over, the experts can speak about the ASF situation in Spain with a sense of relief. In the 2 months prior, however, the lab had been in the eye of the storm, with unlikely levels of coincidence.
After all, it wasn’t much of a surprise that ASF would emerge in Spain, at some point. The virus has been making unexpected moves throughout Western Europe, in recent years, by emerging in Belgium, Germany, Italy and Sweden. So why not in Spain? And it was even foreseen that the Barcelona area – a densely populated area full of highways – would be a likely place for ASF to emerge. Prof Majó says, “Since 2018, there have been reports stating that here, in this area, the risk would be very high. A lot of people, a lot of wild boar and a lot of food waste.”
Nothing short of a nightmare
But to find out that the lab itself would be located right in the heart of the infected zone was nothing short of a nightmare. After all, IRTA-CReSA is one of the few laboratories in Spain with a BSL-3 facility – a highly biosafe lab where research on highly infectious viruses can be conducted (also see the Box). It has been fully equipped since 2006, played an important role during Covid-19 and was also a place of research into the ASF virus.
“The day that we had a PCR positive, we knew that we were in the middle of a hurricane,” says Prof Majó. After all, the virus must have come from somewhere.
Normal life
In normal life, Prof Majó is the head of the Animal Health programme at the Catalan research laboratory IRTA-CReSA and has a background in poultry production. Dr Vilalta is researcher and epidemiologist with a specialisation in PRRS virus; Prof Segalés is researcher and pathologist and is well-known around the world for his contributions on viral diseases. Prof Majó and Prof Segalés are both also teaching at the Autonomous University of Barcelona (UAB). IRTA-CreSA is located on the university’s campus.
Monitoring and analysing of ASF-related samples
If those responsibilities weren’t already enough, as of 25 November 2025, about 40 professionals and PhD students received a huge additional responsibility: the monitoring and analysing of ASF-related samples and carcasses from the direct surroundings. Prof Majó was at the helm, coordinating everything, while Dr Vilalta became involved in analysing epidemiological data on every outbreak. Prof Segalés took care of the pathology – researching carcasses together with a team of 3 other pathologists.
Dr Segalés explains, “On the 25th of November, the first dead wild boar was found, the second one on the 26th. One of them was found here at the UAB campus; the other one in Bellaterra, the closest village. Since 2018, we have had a surveillance plan in place, in Catalonia. All wild boar that die spontaneously from unexplained causes must be analysed. Nothing strange ever happened; carcasses were always negative for CSF, ASF and other diseases. Until November last year, when the big surprise was that they were PCR positive (for ASF, ed.), even with relatively low CT values. This implied that these animals had probably been sick and had died because of ASF.”
Fast-paced steps
Things went fast. Samples had to be sent for confirmation to Spain’s central reference lab in Algete, Madrid, while necropsy was performed on the affected animals. “Definitely all the lesions were there,” says Prof Segalés. “Large spleen and haemorrhages in kidneys and in other organs were all observed.”
He praises the speed with which all steps were in place and communicated. “It was very, very important to be quick, from the first detection to the declaration. This implies that all measures that apply to resources, to close off the area, etc., had to be implemented immediately.”
Consequences
The news that ASF had been found in Catalonia had far-reaching consequences for the swine production in Spain, as export possibilities would seriously be impacted. The consequences for exports to the European Union, United Kingdom and China remained limited, due to regionalisation agreements. Still, other countries around the globe closed their borders.
For IRTA-CReSA, busy times commenced. On top of normal work – which already included the analysis of lumpy skin disease (cattle) and avian influenza (wild birds) – at least 20 wild boar carcasses and/or blood samples would come in for analysis, each day.
“For the Catalan government, having the lab here was very convenient,” Prof Majó says, “because now we were analysing all the animals that tested positive right here, and they were incinerated also here. Carcasses did not have to be transported out of the infected zone to a rendering plant, which was always an issue in other outbreaks.”
Police guarding the lab
To make sure that everything is done ‘by the book’, members of the Mossos d’Esquadra (Catalan police) are therefore guarding the lab. They have the responsibility of overseeing the safety and correct handling of all the carcasses, as well as the disinfection of all vehicles bringing the carcasses to the lab.
The types of work roughly fall into 3 categories. The most frequent type consists of checking blood samples, which are brought to the laboratory by an organisation called “Agents Rurals”. The samples come from wild boar that have been shot further away from the infected zone. Often, it is sufficient to bleed the animals and send the blood sampling for testing. These animals are not expected to be ASF-positive.
The second category of work consists of dead wild boar from the infected zone, including road kill, with one animal being brought in about twice a day. Prof Segalés says, “Sometimes, we get just pieces of carcasses, instead of entire wild boar being found. It can be just pieces of bone from an animal that died many days before and had been foraged.”
Cyanotic carcasses
He continues, “If they are fresh wild boar carcasses, in most cases they are cyanotic, so they are blue. However, wild boar are very dark, so it is not always easy to see. If you see blood from the nostrils, then you can have an idea that this is ASF. Blood may also occur after collision with a car or a train, but in those cases you will also see other trauma. With a newly brought in wild boar carcass, first, we take a blood sample, and then we put it in the refrigerator of the BSL-3 lab. Subsequently, we do the PCR. If this turns out to be negative, the animal is incinerated. But if the animal tests positive, we take it out of the refrigerator and perform a necropsy to analyse the lesions and take more samples.”
The necropsies tend to become “never-ending stories”, according to Prof Segalés, because the outcome is often the same. He says, “We will have to adjust this for future cases. For example, for new cases in unexpected places, it would make sense to perform a necropsy. But for cases from the same location, the same area, doing so is not that important.”
The third category of work is only small and consists of handling captured wild boar on the UAB campus – left-over wild boar from a once flourishing population. Any left-over animals are being caught in traps and are subsequently culled and studied.
MAPA communicating
Such were the additional activities happening at the laboratory. Then, on the 5th of December, the Spanish Ministry of Agriculture, Fisheries and Food (MAPA) communicated openly about the possibility of the emergence of the ASF virus being related to a lab escape. And the only lab in the area doing trials with live virus was IRTA-CReSA.
Both Prof Segalés and Prof Majó found it difficult to hide their surprise about that communication. Prof Majó says, “The day before, we had had a meeting with a team of experts from the European Union. We had indicated that all the protocols seemed to be in order, and we promised we would check more in-depth.”
Prof Segalés says, “In the end, to consider the hypothesis is logical, but the point is…”, he hesitates, as Prof Majó adds, “not as the only one.” Prof. Segalés says, “Considering all the possibilities would have been fair.”
A serious investigation
It meant that a serious investigation had to follow, which involved visits of both the Spanish and the Catalan police. In addition, national media, which had already become more interested in what was going on, increased their presence. At some point, they even started to show up around the laboratory. Dr Vilalta says, “If you wanted to go out to get a cup of coffee or a sandwich, suddenly there were people who started talking to you, telling you they were media, and wanting to know why the police were there.”
Until that moment, the team had been trying to be as cooperative as possible with the local and national media. Until 5 December, the team had been cooperating in a total of 80 media requests. Prof Segalés says, “Working for a research centre, I believe that communication is part of our duty, as well. So, from this point of view, we didn’t have any problems with communicating things.”
Taking a different attitude
Soon, however, the realisation sank in at IRTA-CReSA that, perhaps, it would be best to take a different attitude, to avoid misinterpretation or confusion. Some Spanish media had already been connecting dots. There had been loads of trials with ASF virus, there was construction work going on and, on top of that, the outbreaks had taken place directly around the laboratory.
Prof Segalés says, “A message from the Catalan government and even from our communication department said: let’s stop now, because we have been pointed out as potentially guilty of a potential escape. So, until we have proof of our innocence, we will say nothing from now on.”
Just before New Year
For IRTA-CReSA itself, the question obviously was a matter of introspection. Prof Segalés says, “Although, we also contemplated the possibility of an escape, internally, most of us thought that it was not possible, because of all the measures that had been applied, for a long period of time. We had been working with ASF since 2007, 2008 – so that was 18 years already – and we had never had any problems in this regard.”
Obviously, the outbreak of the Foot-and-Mouth Disease (FMD) virus in 2007 near London, in the United Kingdom, is a good example of a virus escaping from a lab not being impossible. Prof Majó says, “There is a very big difference, however, as FMD can be transmitted through the air. And FMD transmission is much easier.” Indeed – ASF virus is normally found in blood samples, and is generally transmitted when wild boar cannibalise on carcasses of other wild boar.
Wastewater streams could not have been the cause of any leakage either, as Prof Segalés explains. Solid waste from the BSL-3 lab is incinerated and liquid waste is treated. He says, “We only release waste products after certain inactivation conditions have been met and verified.”
Proof of innocence
The first clear proof of the institute’s “innocence” appeared just before New Year’s Eve 2025, when the Catalan Institute for Research in Biomedicine published some research. This compared all strains used in trials, in the last year, with the ASF strain that was found in wild boar roaming north of Barcelona. The result: none were a match. With a smile, Prof Segalés says, “That already was a big relief. But we needed the final confirmation from the reference lab in Algete.”
From that moment on, it was waiting for the reference lab and MAPA to reach the same conclusion and present the irrefutable evidence. It took 6 long weeks before the ministry released the findings from its own research, on 16 February, which indeed boiled down to pretty much the same outcome: the strain of the outbreak did not match any of the strains used for research at IRTA-CReSA.
Remaining questions
Apart from bringing the virus under control – which is difficult as it is – there are still some questions to answer. For instance, where did the virus come from if it had not escaped from the lab? The MAPA report suggested that crossover infection from other wild boar was unlikely, and so was bioterrorism, if only because the strain doesn’t match any known cases. It was most likely that some contaminated material had been introduced into the region, like e.g. in a sandwich.
Prof Segalés says, “Something of pork origin coming from areas of the world in which no sequences are available, because this virus mutates very slowly, which implies that it must exist in a very similar format somewhere in the world. We do not really know where. Of course, we could speculate it could be in eastern European countries, but why not Southeast Asia? I don’t have any idea.”
Likely virus introduction
Interestingly, Prof Segalés also answers the question of when the virus likely was introduced in Spain. He says, “Based on the characteristics, we tried to trace when the virus must have been introduced. We considered that the virus had probably been introduced between September and October (2025, ed.). Usually, the first case that you find is never the real first case.”
Prof Majó adds, “After the first cases were detected we also found bones that were positive, which is why we estimated that the introduction might have been 1.5 to 2 months before.”
Another interesting matter is to know how the Spanish ASFv variety behaves. The MAPA report said that the virus might be less virulent, because the Spanish ASFv strain had a deletion in the genes that regulate virulence.
It’s a hypothesis, Prof Segalés says. The team came across a few live wild boar that had antibodies against the virus. That doesn’t mean per se that these animals had survived an infection. He says, “When you are talking about the incubation period or the duration from inoculation to death, there is always a range. You should not expect that, under natural conditions, everything happens in the same way. Plus, you never know the amount of virus with which these animals became infected. If that would be very low, it would take longer to develop the corresponding lesions.”
Experiments
To get more clarity, experiments are planned involving domestic pigs and wild boar. Prof Segalés explains, “The goal is to study the pathogenesis of this strain and to ascertain if the level of virulence is comparable or not to other genotypes or strains. And, of course, it is very important to see how it behaves – not only in inoculated animals but also in contact animals – and study the way of transmission. And see whether it behaves differently in domestic pigs compared to wild boar. Those are questions that are still on the table.” Studies are planned to start in April 2026.
And the last question: what are the construction works at the lab about? These are the first initial steps for the expansion of the BSL-3 lab, explains Prof Segalés. Those steps relate to the construction of the new additional exterior, whilst the interior of the lab has been able to continue functioning as normal. “We expect that only in 2028 we can connect the new part with the old part. Until that time, nothing at all has been changing.”