A new investigation is being launched after the discovery of a second case of bird flu spreading from cows to humans

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Vaccination remains the most effective strategy for the prevention and control of avian influenza in humans, despite varying vaccine effectiveness among different strains.

This is what the authors of a new review say that examines existing research into bird flu vaccines for humans.

Published in the magazine Human vaccines and immunotherapeuticsThe results of the article are particularly timely following the news on May 22 that the bird flu strain H5N1 has again, for the second time, passed from livestock in America to humans, raising fears of subsequent human-to-human transmission, with possible critical consequences.

In March, cases of bird flu were observed in American livestock for the first time. Since then, this strain has spread mainly from cow to cow, and scientists have discovered very high levels of virus in raw milk (pasteurized milk is safe because it has shown viral RNA, but not infectious virus). However, so far it is known that two people have contracted the bird flu virus. Both patients – American farmers – reported only eye symptoms and with treatment they made a full recovery.

After testing on the first human instance, it was determined that the strain had mutated to be better adapted to mammalian cells, but as long as that human didn’t pass the disease on to another person, the spread likely stopped at that point.

The CDC did just that with the second case released a statement to say it has been closely monitoring flu surveillance systems, especially in affected states. “There are no signs of unusual influenza activity in humans, including syndromic surveillance,” they report.

The concern now, however, is that if H5N1 is given the environment in which it can mutate (such as in small livestock farms) – and this continues long enough – it has the potential to find a combination that can easily spread to humans. .

The results of this new study, conducted by a team from the University of Georgia, USA, suggest that vaccines still remain our “primary defense” against the possible spread of bird flu such as H5N1 and other strains assessed.

“The H5N1, H7N9 and H9N2 subtypes of the avian influenza virus pose a dual threat, not only causing significant economic losses to the global poultry industry, but also posing an urgent public health concern due to documented spillover events and human cases ,” explains lead author. Flavio Cargnin Faccin, who, together with his mentor Dr. Daniel Perez from the University of Georgia, USA, analyzed the current landscape of human vaccine research for this avian flu.

“This deep dive into the bird flu vaccine landscape for humans shows that vaccination remains the most important defense against the spread of these viruses.”

The team examined studies of vaccines tested in mice, ferrets and non-human primates, and clinical trials of avian flu vaccines in humans, assessing both established platforms and promising new directions.

The research conducted shows that inactivated vaccines are a safe and affordable option that mainly activates humoral immunity – the part of our immune system that produces antibodies.

Live attenuated influenza vaccines (LAIVs) are known to induce a broader immune response than inactivated vaccines, activating not only antibody production but also mucosal and cellular defenses. In this review, the authors suggest that this broader response may provide greater protection, although the authors suggest that further research is needed to fully understand and exploit its potential benefits for both human and agricultural applications.

The review also examined alternatives such as virus-like particle (VLP) vaccines and messenger RNA (mRNA) vaccines, which have come to market more recently. Although VLP vaccines for bird flu have limited clinical trial data in humans, results from studies in mice and ferrets were promising, the authors found. mRNA vaccines against the H5N1 and H7N9 avian flu subtypes also generated a rapid and strong immune response in mice and ferrets, and although human data are scarce, results from a phase I trial of an H7N9 mRNA vaccine in healthy humans were ‘encouraging’.

Overall, the team suggests that “exploring and deploying a broad range of vaccine platforms” will be “critical for improving pandemic preparedness and reducing the threat of avian influenza viruses.”

More information:
Pandemic preparedness through the development of vaccines against avian influenza viruses, Human vaccines and immunotherapeutics (2024). DOI: 10.1080/21645515.2024.2347019

Supplied by Taylor & Francis

Quote: New investigation launched after discovery of second case of bird flu spreading from cows to humans (2024, May 29), retrieved May 29, 2024 from https://medicalxpress.com/news/2024-05-discovery-case- avian-influenza-cows.html

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