zoonoses

A review published in Science estimates that 2 % of rodent species are hyper-reservoirs, hosting and transmitting more than three pathogens to humans, including Lyme disease, Lassa fever and plague. In addition, the authors estimate that 10 % of rodents are reservoirs for one to three pathogens. These are especially so-called synanthropic species - animals that live close to humans and are able to adapt to these environments - such as black rats, Norway rats and house mice.

A study carried out in China has analyzed tissues from 461 fur animals, mostly farm-raised. They found 125 virus species, 39 of which presented a high risk of interspecies transmission. According to the authors, who publish the results in the journal Nature, “there is a need for more extensive and regular surveillance to assess the public health risks that could result from fur animal farming”.

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. 

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.

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.

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.

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.