AVIAN INFLUENZA, HUMAN – AUSTRALIA: ex INDIA, H5N1
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International Society for Infectious Diseases
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Date: Wed 22 May 2024
From: Dr Finn Romanes [edited]
The first human case of A(H5N1) highly pathogenic avian influenza
(bird flu) has been confirmed in Australia, in a child recently
returned from India.
The child who became unwell whilst in India was hospitalised upon
return to Australia in March 2024. Influenza A was detected by PCR
during admission, and the child was treated with oseltamivir during a
prolonged stay in intensive care with severe lower respiratory tract
infection and hypoxia with respiratory failure. The child has since
been discharged home and has made a complete recovery.
Genome sequencing conducted at the WHO Collaborating Centre for
Reference and Research on Influenza (Melbourne, Victoria, Australia)
identified the virus as A(H5N1) with a multibasic cleavage site,
confirming highly pathogenic avian influenza.
Blast analysis of the hemagglutinin (HA) sequence revealed the closest
sequence match to be an A/duck/Bangladesh/46162/2020 with 98%
homology. The HA clade has been identified as 2.3.2.1a, a clade which
has previously been detected in Southeast Asia and is distinct from
the HA 2.3.4.4b clade currently circulating in birds and dairy cows
globally.
Blast analysis of the neuraminidase (NA) sequence revealed the closest
sequence match to be an A/chicken/Bangladesh/18-B-569/2022 with 98%
homology. Sequence analysis of the N1 gene indicated sensitivity to
oseltamivir.
Two human cases of A(H5N1) from the same HA clade as this new
Australian case have previously been detected, one in Nepal in 2019
and one in India in 2021. Interview with the child’s family has been
unable to identify a clear acquisition source, with the child having
no interaction with birds, animals or sick human contacts either in
India or Australia, and no geographic or epidemiological links to any
of the previously isolated homologous cases. There was also no known
consumption of undercooked poultry or meat products during the
acquisition period.
Contact tracing did not identify any contact with animals whilst ill
on return to Australia, and there were no ill human contacts
identified and no evidence of any onwards transmission to humans or
animals.
This case highlights the importance of (a) overseas travellers seeking
early diagnosis and care for severe respiratory infection acquired in
countries with known avian influenza, (b) subtyping of influenza
strains in cases of overseas-acquired severe influenza A infection,
and (c) local policies to promote seasonal influenza vaccination for
travellers but also for poultry and pork workers in Australia.
While seasonal influenza vaccination does not protect against avian
influenza infection, national guidelines in Australia recommend
seasonal influenza vaccination for all people aged over 6 months and
include a specific recommendation for poultry industry workers to
receive seasonal influenza vaccination. This policy is intended to
minimise the risk of genetic reassortment in a person with
co-infection due to human influenza and avian influenza viruses, which
could occur while overseas or after exposure to avian influenza during
a local outbreak in domestic flocks in Australia.
The case was reported in a Victoria (Australia) Chief Health Officer
Advisory on 22 May 2024; see
https://www.health.vic.gov.au/health-advisories/human-case-of-avian-influenza-bird-flu-detected-in-returned-traveller-to-victoria.