Bird flu penguins casualty rate
There is no single, reliable “mortality rate” for penguins from H5N1 at specific locations; where confirmed, events are best described as mass-mortality clusters with high carcass counts but unknown attack rates, so assume high case fatality among clinically affected birds and plan accordingly. 1
What the highest-quality, recent wildlife evidence shows
- Chile (2023, Humboldt penguins): 2,788 strandings/deaths recorded Jan–Aug 2023; 2,712 were dead. Only 4/181 tested confirmed H5N1 due to degraded samples, but spatial/temporal linkage supports H5N1-associated mass mortality. Because total exposed/infected denominator is unknown, a true mortality “rate” cannot be calculated; observed outcome is large die-offs with presumed high fatality among clinically affected penguins 1.
- Antarctica (2024–2025): Multiple surveillance efforts near penguin colonies detected H5N1 mainly in skuas with high mortality; environmental and penguin swab RT-PCRs were negative at sampled sites, implying sporadic or low-detectable prevalence in penguins at those times, thus no calculable mortality rate for penguins there 2, 3, 4.
- Earlier penguin studies (pre-panzootic) often found no active influenza A in colonies, underscoring that rates vary by place/time and incursion status 5.
How to communicate risk to stakeholders at affected locations (prioritize morbidity, mortality, QOL of colonies)
- Treat confirmed or suspected H5N1 incursions as high-risk for rapid, localized mass mortality in penguins even when precise case fatality can’t be estimated; immediate carcass removal, access control, and biosecurity are warranted to protect colony survival and ecosystem function 1.
- Avoid over-interpreting low RT-PCR detection in carcasses; poor sample quality commonly underestimates infection, while carcass counts better reflect impact on mortality 1.
- In nearby predator/scavenger species (e.g., skuas), confirmed high H5N1 mortality signals ongoing viral circulation adjacent to penguin sub-colonies; escalate surveillance and protective measures for penguins at those sites 2, 3.
Common pitfalls and how to avoid them
- Pitfall: Reporting “mortality rate” without a known denominator. Avoid by reporting carcass counts, timing, and lab confirmation status, clarifying that case fatality cannot be derived. Use “mass mortality event linked to H5N1” rather than a percent rate 1.
- Pitfall: Assuming absence of virus from negative spot testing. Maintain precautionary controls; serology and predator mortality may indicate recent circulation despite negative swabs in penguins 4, 2.
Practical algorithm for an affected location
- If carcasses rise above baseline and H5N1 is present regionally: declare suspected HPAI mass-mortality event; implement biosecurity, restrict access, and remove carcasses promptly; target fresh carcasses for RT-PCR to maximize confirmation yield; report counts daily. If confirmation obtained in any sympatric species (e.g., skuas), maintain heightened response in penguin colonies due to proximity risk 1, 2, 3.
Notes on human-pandemic guidelines