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In January 2016, highly pathogenic avian influenza (HPAI) A(H7N8) and a low pathogenicity (LPAI) form of the same subtype were found in commercial turkey flocks in Dubois County, Indiana. It was the first time HPAI A(H7N8) had been detected in any species. The Indiana State Department of Health (ISDH) and the Dubois County Health Department (DCHD) led the public health response, the first to put fully into practice monitoring procedures for HPAI responders that the U.S. Department of Agriculture (USDA) and CDC had drawn up, but not published, in 2015. No human infections were found.
The outbreak on the farms
On January 15, 2016, the Indiana State Board of Animal Health told ISDH that HPAI A(H7N8) had been confirmed in a commercial turkey flock. Following USDA guidelines, the board began active surveillance of commercial poultry within 6.2 miles (10 km). By the next day, H7 virus had been found in nine more turkey flocks: eight confirmed as LPAI A(H7N8) and one inconclusive. Two more flocks were classed as dangerous contact premises because they were so close.
Because the HPAI and LPAI strains were thought to be closely related, the board chose to destroy the birds on all 10 infected premises and both contact premises, 414,223 birds in all. The work was done mainly by owners and industry representatives, helped by volunteer offenders from the Indiana Department of Correction, who were paid at the department's standard rate and received medical clearance, N95 respirator fit testing and training that covered the risk of avian influenza spreading to people. The index flock was cleared by January 16 and the rest by January 20. Most carcasses were composted in the barns, the premises were cleaned and disinfected, and restocking was allowed from May 1.
Monitoring the people
Health officials recommended watching responders during the response and for 10 days after their last possible exposure for influenza-like illness, defined as fever with cough or sore throat, or conjunctivitis with or without other symptoms. Every responder was told to seek care and contact public health if symptoms appeared. USDA monitored federal employees and contractors; ISDH and DCHD monitored state and local responders, using procedures adapted from ones written for HPAI A(H5).
| Risk category | Who | How they were monitored |
|---|---|---|
| Some risk | exposed to infected or possibly infected birds or their surroundings without proper protective equipment, or with a breach in it | active: daily contact by visit, phone, text or email |
| Low but not zero risk | exposed while wearing proper protective equipment, or living or working on an infected premises without bird contact | phone calls on the first and last day |
| No risk | not exposed | none |
On-site personnel peaked at 516 on the fourth day, most of them federal employees or contractors. Local health departments and the Department of Correction assessed and monitored 166 state and local responders: 93 farm workers or residents, 67 corrections officers and offenders, and 6 local USDA employees who had finished their work.
- 74 (45%) were monitored for some-risk exposure and 67 (40%) for low-risk exposure; 4 (2%) were monitored with no risk level recorded.
- 7 (4%) had no exposure, 5 (3%) declined monitoring and 9 (5%) were lost to follow-up.
- Of the 145 monitored, 14 (10%) reported current or recent flu-like symptoms. Twelve were tested between January 16 and 22, a median of 1 day after symptoms began, with throat and nose swabs, eye swabs or both. All 12 were negative for influenza A.
The wider response
Indiana opened its Emergency Operations Center on January 15, staffed according to the federal emergency support functions for transportation, emergency management, public health and medical services, hazardous materials, agriculture and law enforcement. The Board of Animal Health led; ISDH supported public health and medical services, and DCHD led locally with Memorial Hospital in Jasper. A state incident management team set up a unified command post with USDA, where ISDH placed a liaison. ISDH also:
- distributed N95 respirators and laboratory testing supplies
- stocked the antiviral oseltamivir at the local hospital
- prepared a demobilization packet for responders
- issued a Health Alert Network advisory to health care providers in Dubois and nearby counties
- set up syndromic surveillance to detect any cases in the community
- wrote recommendations for antiviral use
Why caution was warranted
The risk to people was thought to be low: no human H7N8 infection had ever been reported, and early genetic analysis showed no sign of greater virulence or spread in mammals. But other H7 bird flu viruses have infected people, sometimes causing severe respiratory illness, and a person infected with both a bird and a human flu virus could in theory give rise to a new strain. The HPAI virus was suspected, and later confirmed by genetic analysis, to have arisen by spontaneous mutation of the LPAI virus. A later study found the HPAI strain more virulent in mice and ferrets, while only the LPAI strain spread between them, a worrying combination.
Whether a virus is labeled high or low pathogenicity depends on its genetics and on how badly it sickens poultry. That label does not predict whether it will infect people or how ill they would be, and LPAI viruses can cause severe and fatal human illness. Since many responders worked on both kinds of farm, all were treated alike.
Lessons
The report identified three problems. Responders' contact details reached the county health department late, with complete information arriving only on January 20, five days in, because the animal health response was so urgent and complex. Tears in Tyvek suits were reportedly common when handling birds, so some exposures may have been misclassified. And with so many responders mobilized so quickly, protective equipment and monitoring advice may not have been followed consistently.
The authors recommend clear communication of public health needs to everyone involved; early identification of exposed people, for example through badging; a public health liaison embedded in the unified command post to gather responders' names and contact details; and daily debriefings with safety officers to catch injuries or equipment breaches. In future outbreaks of avian influenza viruses of public health concern, ISDH will recommend active 10-day monitoring for everyone who enters the hot and warm zones of an infected farm, whether or not they wore protective equipment, so that unnoticed breaches are covered too. At the time of the report, USDA and CDC were updating their national monitoring plan to cover all avian influenza viruses of public health concern and to allow passive monitoring of protected responders for H5 and H7 viruses with no history of infecting people.
Sources
- Brown JA, Patel R, Maitlen L, et al. "Public Health Response to an Avian Influenza A(H7N8) Virus Outbreak in Commercial Turkey Flocks — Indiana, 2016." MMWR 67(48). https://www.cdc.gov/mmwr/volumes/67/wr/mm6748a2.htm
- CDC H7N8 update: https://www.cdc.gov/flu/news/avian-influenza-h7n8-update.htm
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