Iowa’s avian flu deaths this fall surpasses fall 2022

Another massive flock of egg-laying hens in Iowa recently was found to be infected by a very transmissible and deadly version of avian flu, which has pushed the total number of affected birds this fall beyond casualties for the same time period last year.

The recent detection of avian influenza was in a flock of about 1.6 million birds in Sioux County, according to the Iowa Department of Agriculture and Land Stewardship. Humans are seldom infected by the virus, but it can spread quickly in domestic flocks and is lethal to the birds. Entire flocks are culled to prevent the virus from spreading.

That incident more than doubled the total affected Iowa birds since mid-October. Infected sites now total 15 — ranging from backyard flocks to immense commercial chicken operations — with nearly 3 million birds.

So far, that is more than triple the rate of detections in October and November over last year. The final virus confirmation last year happened Dec. 12, and over the course of three months about 2.5 million birds were affected last fall.

The death toll largely is driven by the type of facility that is infected. Iowa is the nation’s leading egg producer, and those individual chicken flocks can number in the millions. Commercial turkey flocks often have tens of thousands of birds. The smallest flock affected this fall — a backyard group of different species — had 23.

The virus is often transmitted to domestic flocks by wild, migrating birds that can be asymptomatic.

While the infections in Iowa this fall have been worse than last year, the state largely escaped infections during this year’s spring migration, which was devastating last year. The total number of affected birds in 2022 in Iowa was about 16 million.

That led to the state’s lowest annual egg production in more than a decade, according to U.S. Department of Agriculture data. Iowa produced about 12.2 billion eggs in 2022. That was down from 15 billion the year before and from a high of 17 billion in 2019.

Iowa’s second-lowest production total in recent years was in 2015, when there was also a widespread avian flu outbreak. That year the state produced 12.7 billion eggs.

This year, production has rebounded but will be short of 2021, before the latest outbreaks. Through October, Iowa has produced about 11.4 billion eggs this year and has averaged more than a billion each month, according to USDA data.

The other virus detections in Iowa this fall include:

This article first appeared in the Iowa Capital Dispatch.