#18,357
It's been a little over a month since the last PAHO Epidemiological Update on Avian Influenza, with the newest released yesterday. The report summary states:
Epidemiological Update - Avian Influenza A(H5N1) in the Americas Region - 4 March 2025The full 11-page report is worth reading, and once again PAHO stresses:
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Since 2022 and as of epidemiological week (EW) 8 of 2025, a total of 19 countries and territories in the Americas Region reported 4,713 animal outbreaks of avian influenza A(H5N1) to the World Organization for Animal Health (WOAH), representing 325 additional outbreaks, since the last epidemiological update published by the Pan American Health Organization/World Health Organization (PAHO/WHO) on 24 January 2025.
A total of 74 human infections caused by avian influenza A(H5) have been reported in four countries in the Americas between 2022 and 25 February 2025, with three additional cases reported since the last epidemiological update published by PAHO/WHO.
PAHO/WHO urges Member States to work collaboratively and intersectorally to preserve animal health and protect public health. It is essential that preventive measures for avian influenza be implemented at the source, protocols for detection, notification and rapid response to outbreaks in animals be established, surveillance for both animal and human influenza be strengthened, epidemiological and virological investigations be carried out in relation to animal outbreaks and human infections, genetic information about viruses be shared, thereby fostering collaboration between animal and human health settings, effectively communicating risk , and ensuring preparedness for a potential influenza pandemic at all levels (20, 21).
Reports like this are valuable, but rarely do they convey the full impact of an outbreak. While there are 35 PAHO member nations (plus 4 associate members), less than half have reported H5 (in any host) since 2022. And as the following graphic indicates, very few reports have been submitted from Central and South American countries over the last 30 days.
While this may be reflective of a genuine lull in outbreaks, it may also be a byproduct of `suboptimal' surveillance and reporting. Even here in the United States, reporting of H5N1 infections - particularly in mammals - has been slow in coming.
While governments love to release reassuringly low `official' numbers, the surveillance and reporting of infectious diseases has never been particularly accurate, or all encompassing. As the following CDC graphic illustrates, official numbers often only include the very tip of the pyramid.
Sometimes this is due to mild, or non-remarkable, presentation in the population. Illnesses that mimic viral respiratory infections, are notoriously easy to miss. Other times, there are simply gaps in surveillance and reporting (either intentional or due to a lack of resources).
We can see this demonstrated by the following graphic showing that in the latest CDC COVID Nowcast, only 1 HHS region collected and submitted enough (n=300) sequences to warrant inclusion in the current numbers.
Over the past couple of years, 90% of the world's nations have stopped reporting COVID fatalities or hospitalizations to the WHO (see The Wrong Pandemic Lessons Learned). While COVID is no longer the scourge it once was, for political and economic reasons, we've artificially deflated the numbers in order to speed its departure.
A policy that will pay dividends up until the time a new and more virulent COVID variant emerges, and catches us with our surveillance down. But I digress . . .
The CDC's official case count of H5N1 infections in the United States over the past year (see below) stands at 70, but it doesn't tell the full story. Not included are 7 locally confirmed `probable' cases, and a growing number of serologically positive cases (see here, here, and here) which are not officially counted.
Add in the anecdotal reports of symptomatic farm workers who refused testing (see EID Journal: Avian Influenza A(H5N1) Virus among Dairy Cattle, Texas, USA), and the `official' number of 70 human cases becomes even less representative of reality.
In nearly every risk analysis the authors provide a `confidence level' in the data; usually High, Moderate, or Low.
Increasingly, my confidence in the reporting - even from countries (including my own) which have historically been more `open' to releasing information - has dwindled. Although it is arguably getting worse, it has devolved steadily over the past several years (see 2022's Flying Blind In The Viral Storm).
While I would love to point to the lower number of dairy herds recently reported as infected by H5N1, or the recent slowdown in human infections in the United States (and the world), as proof that the H5Nx threat is declining, the quality of the data is unknown.
I'm sure there are genuine short-term economic or political gains to be had by downplaying or under-reporting HPAI H5, COVID, and other emerging diseases.
And maybe we get very lucky, and H5 really does fade away.
But like with Russian Roulette, this is a game that can only be played for so long before it ends badly.
