Authors’ contributions:
Pablo Plaza: Conceptualization; Data curation; Investigation;
Project administration; Resources; Validation; Visualization;
Roles/Writing - original draft; Writing - review & editing.
Andrea Santangeli: Conceptualization; Data curation;
Investigation; Project administration; Resources; Validation;
Visualization; Roles/Writing - original draft; Writing - review &
editing.
Tommaso Cancellario: Data curation; Resources; Validation;
Visualization; Writing - review & editing.
Sergio Lambertucci: Conceptualization; Data curation; Funding
acquisition; Investigation; Project administration; Resources;
Supervision; Validation; Visualization; Roles/Writing - original draft;
Writing - review & editing.
In late 2020, the Highly Pathogenic Avian Influenza A(H5N1)
(hereafter, H5N1) fired the most severe panzootic ever recorded,
causing alarming mortalities in wildlife and domestic animals, with an
increasing risk to humans 1–4. Almost the
entire world has been affected by H5N1; the virus has expanded to new
regions such as the Americas and Antarctica for the first time in its
evolutionary history 3. However, no cases of
H5N1 have been detected in Oceania to date 5,6(only one human case infected outside this continent
has been reported 7). Regions not
affected by this virus are of epidemiological importance, as they
provide insights about potential limiting factors for its spread (e.g.,
geographic barriers, environmental features, wild species traits and
movement). Moreover, in those areas, there is still time to
prepare efficient preventive and mitigation actions to reduce the impact
of this pathogen, if we can identify potential pathways of virus
arrival. Here, leveraging range maps of suitable host bird
species, we suggest a potential pathway of H5N1 arrival to the Oceania
region that could be important to consider under the current
epidemiological behavior of this virus.
To assess possible pathways of H5N1 arrival to Oceania(specifically: Australia, New Zealand and Tasmania for this
article) we performed a map of risk based on wild bird species already
reported as infected by the virus anywhere in the world. These species
could be considered suitable hosts of the virus. We integrated a list of
H5N1-infected wild bird species reported in the World Animal Health
Information System (WAHIS) database up to April 2024 3and Scientific Committee on Antarctic Research up to November 2024
(SCAR) 8, with species distributions primarily based
on habitat maps (AOH) 9 and, when these were lacking,
bird ranges provided by BirdLife International 10. We
removed records in which infected individuals were not identified at the
species level and cases where individuals were kept in captivity. We
obtained 345 unique wild species found infected by H5N1. To map the risk
of H5N1 infection (i.e., areas where species reported as infected are
distributed), we used the Additive Benefit Function (ABF) in Zonation
v.5 11.
Our risk map shows that Oceania presents a low risk compared with other
regions because it still does not host many species already reported as
infected in the rest of the world (Fig. 1A). However, more than 50
species that live in Oceania have already been infected in other regions
(Supplementary Material Table S1). Many of those species overlap their
distributions in most of the coast of Australia and New Zealand making
this region of high risk (Fig. 1B). Some key susceptible species
reported infected in other regions (e.g., Antarctica and sub-Antarctic
islands) such as Brown skuas (Stercorarius antarcticus ), South
Polar skuas (Stercorarius maccormicki ), Wandering albatross
(Diomedea exulans ) and Giant petrels (Macronectes
giganteus ) are present in the south of Oceania (Fig. 1A). These
species, and especially immature birds, have large movement patterns
(thousands of kilometers), covering areas all around the world at high
latitudes 12 (Fig. 1A). For instance, immature
Wandering Albatrosses tagged in their first year could perform
circumnavigations of the globe and travel up to 185,000 kilometers12,13 (Fig. 1A); this species can travel 8.5 million
kilometers in their entire life of 50 years 13. Since
species mentioned are susceptible and could transport the virus to
distant areas, the risk of its arrival in Oceania throughout the
Southern Ocean Flyway in the short to medium term is rapidly increasing.
Previous studies have sampled thousands of individuals of different wild
bird species across Australia to evaluate the potential arrival of H5N1
and have proposed the East Australasian flyway as a potential pathway of
virus arrival; to date, there is no evidence of any infection with H5N1
in birds there 5,6. While the East Australasian flyway
and its bird species could be considered of high risk for virus arrival5, our map also suggests that other southern flyways
routes and the species using them should be considered to predict the
potential arrival and introgression of the virus into this continent
(Supplementary Material Table S1).
The distribution and movement patterns of Brown, South Polar
skuas, Wandering albatross and Giant petrels encompass Patagonia, in the
southern tip of South America, sub-Antarctic islands, Antarctica, and
include the south of Oceania 12 (Fig. 1A). In Antarctica and the Sub-Antarctic islands, H5N1 cases and
suspected infections in these and other wild birds have been reported
from 2023 to November 2024; at least 70 cases (confirmed and suspected)
were reported in this region 3,8 (Fig.1A). Worryingly, infected and suspected individuals have been found in new
areas to the east of the Antarctic Peninsula, reaching even regions near
the south of Africa (Marion Island, -46.876620, 37.744890: 3 suspected
cases, and Ile de la Possession, -46.427645, 51.748694, 2 suspected
cases) between September and November 2024 (Fig. 1A)8. The virus has potentially traveled around 5,000
kilometers in less than one year, moving from Bird Island (-54.006869,
-38.036471) in October 2023 to the suspected cases of Marion Island in
September 2024, primarily associated with skuas, but also with other
marine birds 8 (Fig. 1A). While the distance from
Marion Island to Australia is approximately 6,500 kilometers, the
species mentioned above have wide movement patterns (Fig. 1A); thus,
those distances may only represent a temporary barrier. This was the
case of South America, where the virus traveled approximately 8,000
kilometers from the Pacific to the Atlantic Ocean, devastating pinnipeds
(e.g., Otaria flavescens ) populations along its trajectory in
less than one year 14. In fact, the
nearest distance between the coast of Antarctica to Australia and New
Zealand is only 3,500 and 2,800 kilometers, respectively; thus, if
infected birds spread across the Antarctic continent to the east,
Oceania could also be at high risk via this pathway.
The epidemiological behavior of the currently circulating H5N1
lineage is continuously changing; the potential for its arrival in
Oceania via the Southern Ocean Flyway could be possible, as shown
(Fig.1A, B). Therefore, Oceania, the last continent free of this highly
dangerous pathogen, is at potential risk of arrival through migratory
birds using the Pacific Ocean (East Asian Australasian Flyway) and via the Southern Ocean Flyway (Fig. 1B). Our maps show that
susceptible host species are present all around the continent but
particularly in the south (Fig. 1B). Considering they are connected with
individuals from other regions 13,15, they
can be infected in some of the places they overlap and act as the
pathway for H5N1 to reach this region.
The information provided here could be useful for authorities
from the countries in Oceania to focus on implementing surveillance
programs taking into account the species and geographical areas of risk
suggested here. It is crucial to be well prepared in advance
with all the information on potential infection pathways to have better
possibilities to deal with this highly virulent and contagious pathogen.
Once arrived, this virus can decimate large populations of wild birds
and mammals, production systems including poultry and dairy farms, and
may even cause human infections 2,4,14. A
transboundary coordinated effort is fundamental to deal with H5N1
spread; our main effort should be to limit the arrival of H5N1 to new
geographical areas as much as possible at the same time of preparing the
regions to reduce the spread as soon as it arrives. To this end, knowing
the potential sites, species that are potential vectors of the virus and
their ecological behavior, would be an advantage towards containing and
mitigating this emerging pathogen that is causing devastating economic
and environmental effects globally.