Bird flu

A team in the US has tested the efficacy of baloxavir, an antiviral already on the market for treating common flu, against avian influenza in mice. The results, published in the journal Nature Microbiology, show that it is more effective than the currently recommended oseltamivir (Tamiflu) except when the infection is via the mouth, in which case it is equally effective. According to the authors, baloxavir ‘could be considered for the potential treatment of serious H5N1 virus infections in humans’.

A team of researchers from the USA has analyzed the B lymphocytes of seven healthy people in whom no exposure to H5 influenza viruses, such as the avian flu virus, had been documented. The results show that they present antibodies capable of recognizing this type of virus, which, according to the authors, could represent “a first line of defense” in the event of a pandemic. The results are published in the journal Science Immunology.

The H5N1 avian influenza virus can be transmitted between mammals, according to a study published in Nature. The research team isolated the virus from the milk of an infected cow in New Mexico (USA) and found that it spreads in mice and ferrets, reaching the mammary glands of both animals. In addition, the virus was also transmitted from infected lactating mice to their offspring. The European Centre for Disease Prevention and Control (ECDC) has issued a press release on Monday recommending increased surveillance for these viruses.

The World Health Organisation (WHO) has announced that a 59-year-old man infected with the H5N2 avian influenza virus died in Mexico on 24 April. This is the first confirmed human infection with the virus. The patient had multiple underlying medical conditions and had been bedridden for three weeks for other reasons before showing symptoms. The source of infection is unknown. The WHO assesses the risk to the general population as low. 

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.

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.

Outbreaks of highly pathogenic H5N1 avian influenza have been increasing since 2021, but in recent months have evolved into what is known as a 'global panzootic' affecting all types of wild birds and new continents, but also mammals such as mink and sea lions. At a briefing organised by SMC Germany, in collaboration with SMC UK and SMC Spain, three experts discussed the situation, the level of risk and possible next steps.

The H5N1 virus that is causing an unprecedented epidemic among wild and domestic birds has a very low capacity to infect humans. The three cases where infection has been found have been due to close contact with dust raised during the handling of affected poultry.