Credit CDC
#18,289
While we await further news from the epidemiological investigation into the Missouri H5N1 case - one which reportedly had no known animal contact - the CDC has updated their guidance page on Influenza antiviral Chemoprophylaxis of Persons Exposed to novel flu viruses which was originally posted in June.
The updated document has been amended to include exposure to Birds or Other Animals with novel influenza A viruses, and now includes exposure to food products (e.g. raw milk), contaminated surfaces (e.g. bedding, feed or water, waste products, etc.), and even locations (e.g. farms, poultry markets, etc.).The original document primarily dealt with individuals exposed to HPAI infected birds (or wild birds with Unknown Avian Influenza A Virus Infection Status).
This guidance is designed primarily for clinicians and public health officials, as it expands the scope of when and where antiviral post-exposure prophylaxis may be considered.
As we've seen previously, the word `interim' in the title is there because guidance is subject to change as more is learned about the threat. As they state: There is limited experience with these newly detected viruses to inform public health guidance regarding use of antiviral chemoprophylaxis.
First the updated guidance, after which I'll have a postscript.
Interim Guidance on Influenza Antiviral Post-exposure Prophylaxis of Persons Exposed to Birds or Other Animals with Novel Influenza A Viruses Associated with Severe Human Disease or with the Potential to Cause Severe Human Disease
WHAT TO KNOW
This document provides interim guidance for clinicians and public health professionals in the United States on antiviral chemoprophylaxis of persons exposed to birds or other animals infected with novel influenza A viruses associated with severe human disease or thought to have the potential to cause severe human disease.
Background
Examples of novel influenza A viruses with the potential to cause severe human disease can be found on Bird Flu Virus Infections in Humans, including highly pathogenic avian influenza A(H5N1) and A(H5N6) viruses, and avian influenza A(H7N9) virus. A novel influenza A virus is considered to have the potential to cause severe human disease if previous cases of infection with the same hemagglutinin subtype [e.g., HPAI A(H5) or A(H7) viruses] have been associated with severe human disease or in the setting of recent human infections with novel influenza A virus subtypes for which limited data on disease severity are available. Additionally, more information about specific novel influenza A viruses and past reported human infections with novel influenza A viruses is available.There is limited experience with these newly detected viruses to inform public health guidance regarding use of antiviral chemoprophylaxis. However, these viruses are thought to have the potential to infect people and cause severe illness. Rare human infections with novel influenza A viruses have been documented in the U.S. since 2002. CDC will update this guidance as additional information becomes available.
Exposure to Birds or Other Animals Infected with Novel Influenza A Viruses
Persons with recent exposure (within 10 days) to novel influenza A viruses include exposure to A(H5) or A(H7) virus-infected animals.
Close exposure is defined as being within approximately 6 feet of birds or other animals with confirmed novel influenza A virus infection by A(H5) or A(H7) viruses. The risk of infection with novel influenza A viruses is higher in people with unprotected exposures (e.g., not using recommended respiratory and eye protection) than in those who used such protective equipment.
See Also:
Case Definitions for Investigations of Human Infection with Avian Influenza A Viruses in the United StatesBird or other animal exposures can include, but are not limited to:
Exposure to Birds or Other Animals with Unknown Novel Influenza A Virus Infection Status
More information on persons with unprotected exposure (e.g., not using respiratory and eye protection) can be found here: Case Definitions for Investigations of Human Infection with Avian Influenza A Viruses in the United States.
It is not possible to know whether well-appearing, sick or dead wild birds or other animals are infected with novel influenza A viruses until they are tested. More information can be found at:
Information for People Exposed to Birds or Other Animals Infected with Avian Influenza Viruses
Information Specific to Hunters of Wild Waterfowl
Download
Monitoring of Exposed Persons
Exposed persons should monitor themselves daily for signs and symptoms of new illness for 10 days after the last known exposure. Signs and symptoms may include fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue, eye redness (or conjunctivitis), shortness of breath or difficulty breathing. Fever may not always be present. Less common signs and symptoms are diarrhea, nausea, vomiting, or seizures.
Any exposed person who develops any new illness symptoms such as those listed above, and particularly any new respiratory symptoms (e.g., cough, sore throat, shortness of breath, difficulty breathing), conjunctivitis, or other symptoms, with or without fever (see clinical criteria) should be promptly tested for novel influenza A virus infection.
Post-exposure Chemoprophylaxis of Exposed Persons
Post-exposure prophylaxis (PEP) with influenza antiviral medications can be considered for exposed persons. Decisions to initiate post-exposure antiviral chemoprophylaxis should be based on clinical judgment, with consideration given to the type of exposure (e.g. without use of respiratory and eye protection), duration of exposure, time since exposure (e.g. less than 2 days), known infection status of the birds or other animals the person was exposed to, and whether the exposed person is at higher risk for complications from seasonal influenza.
(Continue . . . )Chemoprophylaxis is not routinely recommended for personnel involved in culling non-infected or likely non-infected bird populations. Chemoprophylaxis is also not recommended as a control measure for personnel involved in handling sick birds or decontaminating affected environments (including animal disposal) who used proper personal protective equipment.
- If PEP is initiated, antiviral post-exposure prophylaxis should begin as soon as possible (ideally within 48 hours) after the first exposure.
- Oral oseltamivir at treatment dosing frequency (one dose twice daily) is recommended instead of the typical antiviral chemoprophylaxis regimen (once daily) for seasonal influenza. All human infections with highly pathogenic avian influenza A(H5N1) virus in the U.S. have been with viruses susceptible to oseltamivir.
- Antiviral post-exposure prophylaxis with oseltamivir (twice daily) should be continued for 5 or 10 days. If the exposure was time-limited and not ongoing, the recommended duration is 5 days from the last known exposure. If the exposure is likely to be ongoing, a duration of 10 days is recommended because of the potential for prolonged infectiousness from the infected animal(s).
- Specific dosage recommendations for treatment by age group are available at Recommended Dosage and Duration of Influenza Antiviral.
- This recommendation for oral oseltamivir with twice daily antiviral post-exposure prophylaxis dosing is based on limited data in animals that support higher chemoprophylaxis dosing for avian influenza A(H5N1) virus infection 1, and on the desire to reduce the potential for development of antiviral resistance while receiving once daily chemoprophylaxis if infection occurred 234.
- To support post-exposure prophylaxis with oseltamivir using twice daily dosing for novel influenza A viruses associated with severe human disease, including highly pathogenic avian influenza A(H5N1) virus, CDC issued Emergency Use Instructions (EUI) for oseltamivir.
The expansion of potential risk factors in today's guidance more closely aligns with the warnings we've seen issued for years by Hong Kong, China, and other avian-flu hit regions. Hong Kong's CHP continually warns:
- Travellers to the Mainland or other affected areas must avoid visiting wet markets, live poultry markets or farms. They should be alert to the presence of backyard poultry when visiting relatives and friends. They should also avoid purchasing live or freshly slaughtered poultry, and avoid touching poultry/birds or their droppings. They should strictly observe personal and hand hygiene when visiting any place with live poultry.
Transmission
The most common way for the virus to enter a territory is through migratory wild birds. The main risk factor for transmission from birds to humans is direct or indirect contact with infected animals or with environments and surfaces contaminated by feces. Plucking, handling infected poultry carcasses, and preparing poultry for consumption, especially in domestic settings, may also be risk factors.
And just two weeks ago the WHO published Interim Guidance to Reduce the Risk of Infection in People Exposed to Avian Influenza Viruses, which lists a number of `risk factors', including:
- keep live poultry in their backyards or homes, or who purchase live birds at markets;
- slaughter, de-feather and/or butcher poultry or other animals at home;
- handle and prepare raw poultry for further cooking and consumption;
Most people are unaware that LBMs (live bird markets) exist in the United States (see CIDRAP On LPAI H5 Detection At Live Markets In 3 States). In a 2021 study, Live Bird Markets of the Northeastern United States, the authors reported 84 LBMs in New York State alone.
Of course, there are more than 1 million duck hunters in the United States & Canada, and millions more who hunt turkey, and other game birds. Their birds must all be field dressed, or otherwise prepared.
The reality is, while the risk of exposure to HPAI may still be considered low, it is increasing over time. And activities we never gave a second thought to before, may need to be revised or reconsidered.
