#18,909
While avian flu remains chronically (and massively) under-reported around the globe, we did enjoy a bit of a respite over the warmer months, when migratory birds retreated to their high latitude roosting areas for the summer.
But over the past 6 weeks we've seen a robust return of avian flu activity - much earlier than usual - both in North America and much of Europe. Details on the genotypes returning this fall have been slow in coming however.
The sharing of avian flu data has always been problematic, with many countries either unable, or unwilling - due to political, economic, or societal reasons - to disclose outbreaks or share sequences in a timely fashion.
As we saw last March in Nature: Lengthy Delays in H5N1 Genome Submissions to GISAID, it takes an average of 7 months for sequences from non-human hosts to be published.
Yesterday PAHO released their latest epidemiological update on HPAI H5N1 - the first since May - which recaps the 2024-2025 avian flu season, and (repeatedly) urges member nations to share data.
I've only posted some excerpts below, so follow the link to read the full 12-page PDF. I'll have a brief postscript when you return.
Global Context
In 2020, the highly pathogenic avian influenza (HPAI) virus1 subtype H5N1 clade 2.3.4.4b caused an unprecedented number of deaths among wild birds and poultry in numerous countries in Africa, Asia, and Europe (1). In 2021, this virus spread through the main migratory routes of waterfowl to North America and, in 2022, to Central and South America (1). By 2023, outbreaks in animals had been reported by 14 countries and territories, mainly in the Americas (1, 2).
In recent years, there has been an increase in the detection of A(H5N1) viruses in non-avian species worldwide, including terrestrial and marine mammals, both wild and domestic(companion and production). Since 2022, 22 countries on three continents, including the Americas, have reported outbreaks in mammals to the World Organization for Animal Health(WOAH) (3).
Historically, since the beginning of 2003 and as of 25 August 2025, 990 human cases of avian influenza A(H5N1), including 475 deaths (48% fatality rate), were reported to the World Health Organization (WHO) from 25 countries worldwide (4).
Summary of the situation in the Americas Region
Since 2022 and as of epidemiological week (EW) 41 of 2025, a total of 19 countries and territories2in the Americas Region reported 5,063 outbreaks3 of avian influenza A(H5N1) to WOAH (3), representing 115 additional outbreaks since the last epidemiological update on avian influenza A(H5N1) published by the Pan American Health Organization/World Health Organization(PAHO/WHO) on 15 May 2025 (3, 5)
Between 2022 and 14 October 2025, a total of 76 human infections caused by avian influenza A(H5), including two deaths, have been reported in five countries in the Americas, with one additional case since the last epidemiological update on avian influenza A(H5N1) published by PAHO/WHO on 15 May 2025 (Figure 1) (5-7).
The most recent case of human infection with avian influenza A(H5) reported in the Americas Region was recorded in Mexico on 2 October 2025 (6,7), in addition to the case reported in Mexico on 2 April 2025 (8-10). The remaining cases are distributed as follows: 71 cases in the United States of America—one in 2022 and 70 since 2024(11), one case in Canada confirmed on 13 November 2024 (12), one case in Chile reported on 29 March 2023 (13), and one case in Ecuador reported on 9 January 2023 (14).
(SNIP)Recommendations for Member StatesWhile avian influenza outbreaks largely affect animals, they pose ongoing risks to public health. PAHO/WHO, in conjunction with the Food and Agriculture Organization of the United Nations(FAO) and WOAH, urges Member States to work collaboratively and intersectorally to preserve animal health and protect human health (1, 2, 19-21).The sporadic cases of avian influenza A(H5N1) clade 2.3.4.4b detected in humans are mostly associated with direct contact with infected animals and contaminated environments. Current evidence suggests that the virus does not appear to be transmitted from person to person. However, it is imperative to strengthen intersectoral surveillance to detect any possible changes in this situation (22, 23).Research is ongoing to determine the risk to humans from consuming raw or unpasteurized milk contaminated with the influenza A(H5N1) virus. The FAO and WHO recommend consuming pasteurized milk due to the potential health risks associated with various zoonotic pathogens (19-21). There is no evidence to suggest that the influenza A(H5N1) virus or other avian influenza viruses can be transmitted to humans through the consumption of properly prepared and cooked poultry or eggs (19-24).WOAH has specific recommendations on avian influenza situation in birds and mammals. These recommendations advise countries to maintain heightened surveillance of the disease in domestic and wild birds, preventing the spread of the disease through the implementation of biosecurity measures (25).(SNIP)PAHO/WHO urges Member States to work collaboratively and intersectorally to preserve animal health and protect public health. It is essential to implement preventive measures against avian influenza at its source, establish protocols for detection, notification, and rapid response to outbreaks in animals, strengthen surveillance of animal and human influenza, conduct epidemiological and virological investigations of animal outbreaks and human infections, share genetic information on viruses, thereby fostering collaboration between animal and human health settings, effectively communicating risk, and ensuring preparedness for a potential influenza pandemic at all levels (30, 34, 35).
Although there are long-standing international agreements to report novel virus detections to the WHO/PAHO with 24-hours - the reality is there are no substantial penalties for non-compliance (see From Here To Impunity) - and many countries have decided it is in their best interest to hold their cards close to their vest.
This latest PAHO update (once again) calls repeatedly for stronger data sharing, greater transparency, and better intersectoral coordination among member states; stating that major gaps exist in both surveillance and testing.
While couched in `diplomatic' language, the message is pretty clear; member nations need to do more if a larger avian flu disaster is to be avoided.
When describing the list of things that nations need to do, this update uses the phrase: `It is imperative . . . ', once, `It is essential . . . ' no less than 3 times, and `PAHO urges Member States . . . ' a total of 4 times.
None of this is new, of course. The WHO and PAHO have long called for greater transparency, but progress has been slow in coming, and in some cases, has even been losing ground.
While some countries may find a `don't test, don't tell' strategy to be politically or economically attractive in the short run, we risk sleepwalking our way into the next pandemic.
