Spain informed the World Health Organization (WHO) of what it believes may be a case of human-to-human transmission of the A(H1N1)v swine influenza virus, according to a spokesperson for health authorities in Catalonia quoted by Reuters on Friday.
The development brings swine flu back into focus, this time amid concerns over potential human transmission and an unclear source of infection.
Health authorities in the region of Catalonia confirmed a human case of the A(H1N1) virus in the city of Lleida. The infection was diagnosed on February 11 in a patient with underlying chronic conditions who had visited a hospital in late January for a routine check-up without notable respiratory symptoms.
Notably, neither the patient nor close contacts had any known exposure to pig farms or swine, prompting authorities to launch a full epidemiological and laboratory investigation. Spain’s Health Alerts and Emergency Coordination Center was notified and subsequently reported the case to the WHO in line with International Health Regulations.
This marks the fourth recorded case in Spain since 2009 and the second in Catalonia within three years. It is, however, the first detected outside a farm environment in 17 years.
Authorities emphasized that the risk to the general population remains “very low.” Direct and unprotected contact with pigs remains the most common transmission route. Testing of close contacts returned negative results, and laboratory error or sample contamination has been ruled out.
Parallel research findings from the Netherlands offer broader insight into the trajectory of swine influenza viruses in Europe.
A study conducted between July 2023 and September 2025 analyzed 2,237 biological samples from pig, including nasal secretions and saliva, and detected influenza viruses in 484 samples.
Researchers found that the viruses had mutated over time, with some showing genetic similarities to human influenza strains, suggesting instances of transmission from humans to pigs.
However, no new hybrid strains resulting from mixing between swine, human, and avian influenza viruses were identified, a scenario typically viewed as higher risk due to its pandemic potential.
The study, conducted by several Dutch research and health institutions, also tested 25 variants of swine influenza against existing antiviral medications. Results indicated that currently available treatments remain effective.
Beyond public health, the issue carries significant economic implications for Spain, Europe’s largest pork producer.
The country exports nearly €9 billion worth of pork and related products annually. Pork is Spain’s second-largest agricultural export after olive oil, with exports reaching €6.09 billion last year, according to the Financial Times.
Separately, an outbreak of African swine fever, distinct from swine influenza and not transmissible to humans, has led to the suspension of roughly one-third of Spain’s pork export certificates by foreign governments.
Japan and Mexico have halted all imports, while China, the largest buyer of Spanish pork, suspended imports specifically from Barcelona province.
African swine fever does not infect humans but is highly contagious and often fatal among pigs and wild boars. It can spread via infected animals, contaminated footwear, vehicle tires, or meat products. Spain’s last recorded case prior to the current outbreak was in 1994.
The sector, which supports around 400,000 direct and indirect jobs, now faces a dual challenge: containing the outbreak from a health perspective while preventing further trade restrictions. Under European rules, internal bans are limited to a 20-kilometer radius around outbreak sites, though external markets often adopt stricter measures.
Current data does not indicate the emergence of a dangerous new variant, either in Spain or the Netherlands.
Human infections with swine influenza remain rare and are generally mild. The WHO has also reiterated that the virus is not transmitted through the consumption of pork products.
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