Australia's imported H5N1 case linked to South Asian clade

News brief

An imported avian flu case involving an Australian child who contracted the virus in India involves the South Asian clade that is known to circulate in birds in India and Bangladesh, two researchers from the University of New South Wales reported today, based on data from GISAID, the Global Initiative on Sharing All Influenza Data.

H5N1 particles
NIAID/Flickr cc

The clade is different than the clade spreading globally in birds, with occasional spillovers into animals and humans. The South Asian clade is also distinct from an older clade known as that is circulating in poultry Cambodia and Vietnam, also with rare jumps to humans.

Tests reveal H7N3 in recent Australian high path poultry outbreak

In another Australian avian influenza development, Agriculture Victoria said today that it has confirmed highly pathogenic H7N3 as the cause of poultry deaths in an outbreak at a layer farm near Meredith. 

Officials said illnesses in humans who have contact with sick animals are possible, but the overall threat is low.

The department has imposed poultry movement restrictions in the area near the outbreak farm, and it urged bird owners to double down on their biosecurity measures.

High-dose influenza vaccines outperform standard-dose in preventing hospitalization

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A new study from Danish researchers finds that high-dose flu vaccines reduced the incidence of pneumonia- and influenza-related hospitalization (P&I), but there was no difference in death rates between recipients of high-dose and standard-dose vaccines. The study is published in the Journal of Infection. 

High-dose influenza vaccine (HD-IV), which contains four times as much hemagglutinin as standard-dose influenza vaccine (SD-IV), was designed to address lower protection from SD-IV in adults 65 and older. 

Older adults are the most at risk for flu-related complications, and HD-IV has been demonstrated to induce higher antibody responses and significantly reduce the incidence of laboratory-confirmed influenza among older adults in multiple randomized trials, the authors said. 

No difference in all-cause mortality 

In the current study, the authors conducted a meta-analysis of all studies reporting outcomes of HD-IV compared to SD-IV regarding P&I hospitalization, all-cause hospitalization, and all-cause death in adults 65 and older over at least one flu season since 2009. Overall, their analysis included 105,685 participants with a mean age of 66 to 85 years.

HD-IV recipients demonstrated a P&I hospitalization rate of 0.8%, compared to 1.1% in the SD-IV group, for an overall vaccine efficacy of 23.5% (95% confidence interval [CI], 12.3% to 33.2%). For all-cause hospitalization, 14.1% of HD-IV recipients experienced hospitalization during the follow-up period, compared with 15.2% of SD-IV recipients, resulting in a vaccine efficacy of 7.3%.

The fixed-effects model indicated no difference in overall treatment effect between HD-IV and SD-IV regarding all-cause death.

“The fixed-effects model indicated no difference in overall treatment effect between HD-IV and SD-IV regarding all-cause death,” the authors said. 

H5N1 avian flu viruses can persist on milking equipment surfaces

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The H5N1 avian influenza virus infecting dairy cows can persist and remain infectious in unpasteurized milk on milking equipment surfaces for a long period, researchers from the University of Pittsburgh and Emory University reported yesterday in a preprint study.

milking parlor worker
U. J. Alexander / iStock

In experiments designed to help flesh out the risk to dairy workers, they examined the persistence of H5N1 in unpasteurized milk on surfaces found in milking equipment, including the inflation rubber liners and stainless steel, which make up the "claws" in milking machines that attach to udders.

The group noted steps involved in attaching the milking machine to the udders can spread contaminated milk to the workers at several points, including when the milk is stripped by hand—producing spatters and aerosols — before the machine is attached. Release of the machine at the end of milking can spray workers, and surrounding equipment can also release aerosols. 

"Milking often takes place at human eye level, with the human workspace physically lower than the cows, which increases the potential for contact of infectious milk with mucus membranes. Currently, no eye or respiratory protection is required for dairy farm workers," they wrote.

Threat to workers, clues for cow-to-cow spread

They found that H5N1 remained infectious in unpasteurized milk on rubber liners and stainless steel for more than an hour. They also conducted similar tests using the 2009 H1N1 virus and found that it was a good surrogate virus for further tests, and found the virus persists on the rubber surface for at least 3 hours and at least 1 hour.

The team said the findings underscore the risk of contaminated surfaces to dairy workers and suggest that contaminated milking equipment may be partly responsible for cattle-to-cattle spread on affected dairy farms.

Promising preclinical findings for mRNA vaccine against global H5N1 avian flu clade

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A preclinical study of a monovalent mRNA vaccine that targets the H5N1 avian flu clade circulating in multiple world regions is immunogenic and protective, researchers from the University of Pennsylvania and St. Jude Children's Research Hospital reported today in Nature.

vaccine vials
Guschenkova / iStock

The team's goal was to develop tailor-made vaccines matched to flu strains that have high pandemic potential. They first reported those findings in a preprint study in April 2023.

In mice, the vaccine prompted a robust antibody response, and the antibodies neutralized different clade viruses. Experiments on ferrets showed similar results, and the group's challenge studies in ferrets found the vaccine protected the animals from disease and death.

Scientists working on more closely matched version

Scott Hensley, PhD, professor of microbiology at Penn Institute for Immunology and one of the study authors, said on X today that the team is producing updated versions of the vaccine that more closely matches slightly drifted strains circulating today. 

At a briefing yesterday, federal health officials said discussions are still underway with mRNA vaccine makers Pfizer and Moderna. An announcement is expected soon on how they might be involved the development of vaccines against H5N1.

International scientists propose additions to dengue virus classification system

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Mosquito biting person
James Gathany / CDC 

An international group of experts led by the Yale School of Public Health has proposed adding two sub-classifications to the current dengue virus (DENV) nomenclature to help identify and track strains of potential epidemiologic or clinical importance.

The proposed additions, published on the preprint server medRxiv, split the current genotypes of the mosquito-borne virus into "major" and "minor" lineages to provide more spatiotemporal details, offer ways to assign lineages to sequence data, and propose new lineages.

DENV "is currently causing epidemics of unprecedented scope in endemic settings and expanding to new geographical areas," they wrote. "It is therefore critical to track this virus using genomic surveillance. However, the complex patterns of viral genomic diversity make it challenging to use the existing genotype classification system."

Additions may improve inter-group communication

On a website, the researchers describe their classification assignment tool and how to use it. They also updated the viral genotype definitions to reduce the number of genomes that are unassigned or amorphously categorized as "related."

It is imperative to have a precise and common language to monitor continued DENV transmission in different spatio-temporal scales; and that this is communicable to clinicians and public health officials who may not have a background in genomics.

The team said the added major and minor lineages will aid country- and research group–level discussions of relevant dengue virus diversity.

"With the implementation of interventions (e.g. vaccines, Wolbachia-infected mosquitoes) that may eventually select for specific viral lineages, it is imperative to have a precise and common language to monitor continued DENV transmission in different spatio-temporal scales; and that this is communicable to clinicians and public health officials who may not have a background in genomics," the study authors wrote.

"Moreover, the proposed lineages are robust to classification using partial genome sequences," they added.

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