The strain of African swine fever (ASF) identified in wild boars in Cerdanyola (Catalonia) is different from those handled at the IRTA-CReSA research facility, according to genetic analysis carried out by the Institute for Biomedical Research (IRB Barcelona).
Catalonia’s regional agriculture minister, Òscar Ordeig, presented the results this week after the virus was sequenced by IRB scientists. ALSO READ: Spanish police search laboratory near Barcelona in African swine fever outbreak investigation.
IRB received 19 virus samples from CReSA and has so far examined 17 of them. Two additional samples, which had been kept frozen for more than five years, are still awaiting analysis.
Researchers concluded that the viral DNA does not correspond to known reference strains and suggested it could be a previously unidentified variant with reduced virulence.
Although the findings are not definitive, they have been forwarded to Spain’s central Ministry of Agriculture, so that an official assessment can be prepared.
The IRB study forms part of a broader investigation by the Catalan authorities into how the outbreak began. This process has also included an audit of the IRTA-CReSA facilities, which found no security breaches.
Addressing the media, the agriculture department’s Cristina Massot and IRB researcher Toni Gabaldón emphasised that the current report does not allow CReSA to be excluded as a possible source. They stressed that the final determination rests with Spain’s designated European reference laboratory in Madrid.
Gabaldón underlined that both laboratories use the same scientific methods. ‘I would expect the same results,’ he said, while advising patience until the official conclusions are released.
None of the samples analysed matched the virus detected in the first two wild boars found dead in Cerdanyola, on the outskirts of Barcelona.
The genetic sequences also fail to correspond to any of the approximately 800 known ASF variants worldwide. The closest similarity was to the Georgian strain, though it differs by 27 mutations.
On the basis of this evidence, IRB scientists believe the virus is a newly evolved, low-virulence form that emerged through gradual genetic changes. Gabaldón noted that the exact origin of the outbreak may never be fully established, leaving only plausible explanations rather than certainty.
Meanwhile, on Monday, the Ministry of Agriculture confirmed that two more wild boars had died from ASF, raising the total number of confirmed cases to 29.
All affected animals have been found within six kilometres of the location where the initial case was detected, meaning no additional municipalities have been impacted.
As a containment measure, authorities have designated a high-risk zone extending six kilometres from confirmed cases. Entry to forests, riverbanks, meadows, and non-urban parks or paths within this area is currently prohibited.
These restrictions do not apply to private residences, indoor commercial premises, restaurants, or sports facilities.
Visitors to natural areas such as Collserola Natural Park and Serralada de Marina in Catalonia are advised that sections of these parks fall within the restricted zone, including parts of Cerdanyola del Vallès, Sant Cugat del Vallès, and Montcada i Reixac.
Officials reiterated that African swine fever poses no risk to humans, and that the measures are solely intended to limit transmission among wild and domestic pig populations.
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La seqüenciació genòmica de l’IRB confirma que les 17 soques amb les quals treballaven el CReSA i altres laboratoris no coincideixen amb la soca del brot actual de pesta porcina africana.
— Òscar Ordeig (@oscarordeig) December 30, 2025
Demanem prudència i esperem les conclusions de la resta de les investigacions en curs. pic.twitter.com/jBI3jv6M2Y
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