National Institute for Agricultural and Food Research and Technology (INIA-CSIC)

The European Centre for Disease Prevention and Control (ECDC) reported that on January 29th, Spanish authorities notified a possible case of human infection with swine flu virus A(H1N1)v in a worker from a Catalan pig farm. After being diagnosed with bronchitis, subsequent laboratory analyses confirmed it as swine flu A(H1N1)v. The ECDC informs that the patient has fully recovered, and to date, no new cases have been detected among close contacts or among the worker's colleagues at the farm.

A review examines the role of domestic and semi-domestic animals, such as cats, in the emergence of potential zoonoses due to their close contact with humans. The paper, published in the journal Science Translational Medicine, concludes that companion animal health risks will become increasingly problematic with climate change and rapid urbanisation.

An international group of scientists has studied epidemiological data since 2005 and more than 10,000 viral genomes to conclude that the epicentre of H5 avian influenza has shifted from Asia to parts of Africa and Europe. New lineages have emerged from these regions between 2020 and 2022, which evolved by genetic reassortment with low pathogenic viral variants as they spread. According to the authors, who publish their findings in the journal Nature, the increasing persistence of avian influenza in wild bird populations may be driving the evolution and spread of new strains.

Since the first case of epizootic haemorrhagic disease (EHD) in Spain was detected in cattle in November 2022, it has spread among farms in several autonomous communities in dozens of outbreaks. The mosquito-borne disease does not affect humans, but has the potential to cause economic losses.

Influenza A can cause influenza in humans, birds, pigs, and other mammals. In 2009 and 2010, a pandemic caused by the pdm09 strain—popularly called 'swine flu' because it contained genetic sequences from avian, swine, and human influenza—caused thousands of human deaths worldwide. Since then, this lineage has crossed over 370 times from humans to pigs in the United States, according to a study published in PLOS Pathogens. The research also indicates that the circulation of the virus among pigs may cause further evolutionary changes in this lineage, which would increase the risk of the virus passing back to humans.

According to a statement issued Monday by the World Health Organisation (WHO), Poland has reported that "unusual" cat deaths have been found in several areas of the country. Of the 47 samples tested (46 from cats and one from a caracal, another type of feline), 29 were positive for the avian influenza A(H5N1) virus. The surveillance period for all contacts has now ended and no contacts have shown symptoms. According to WHO, "sporadic A(H5N1) infections of cats have been reported previously, but this is the first report of a large number of infected cats in a large geographical area within a country".

Although outbreaks of H5N1 avian influenza have reached record numbers in recent years, human infections remain anecdotal. A study published today in Nature identifies a protein responsible for inhibiting the replication of this virus in humans, while 'human' flus are able to evade it. The authors propose that this protein with antiviral activity evolved in primates and consider that resistance or sensitivity to it should be taken into account when assessing the zoonotic potential of avian influenza viruses.

Analysis of the two asymptomatic cases of H5N1 avian influenza detected in Spain in autumn 2022 in workers at a poultry farm in Guadalajara has confirmed the theory that no actual infections occurred, but that both were in contact with genetic material of the virus found in the environment. Spain has recently modified its protocols, according to the analysis published in Eurosurveillance.

On 27 September, the National Microbiology Centre detected a positive H5N1 avian influenza in a worker at a poultry farm in Guadalajara (Castilla-La Mancha). The sample was taken on the 23rd and the affected person remained asymptomatic until he tested negative, according to Animal's Health.

In the first months of 2022, avian influenza has hit birds in Spain with unprecedented intensity. All outbreaks are now closed and the epidemiological situation is favourable, but we must not let our guard down. The risk of the virus jumping to humans is considered low.