What to know
Monitoring exposed individuals can help to rapidly identify human cases, provide appropriate treatment, prevent onward spread, and help understand the scope of human risk.
Background
CDC recommends that all persons exposed to highly pathogenic avian influenza (HPAI) A(H5N1) virus infected birds, cattle, or other animals be monitored for symptoms consistent with HPAI A(H5N1) virus infection starting the first day (day 0) of exposure and continuing until 10 days after the last exposure. Monitoring exposed individuals can help to rapidly identify human cases, provide appropriate treatment, prevent onward spread, and help understand the scope of human risk. Between February 2022 and May 2024, at least 9,500 people with potential exposure to HPAI (H5N1) in the United States have been monitored.
Exposures include but are not limited to contact with: infected birds (including poultry, wild birds, and backyard birds), livestock (including dairy cows), or other animals; carcasses of birds, livestock, or other animals; feces or litter; raw cow milk; surfaces and water that might be contaminated with animal excretions.
Recommended types of monitoring:
Active monitoring is recommended for individuals who have had unprotected (i.e. have not consistently or correctly used personal protective equipment (PPE)) exposures to HPAI A(H5N1) virus infected animals or their environments.
Most exposed dairy farm workers fall in this category.
- Local or state health departments contact exposed persons directly about the development of any signs and symptoms of infection, either daily or on a modified schedule (i.e., day 0, 5, and 10).
- Can be done utilizing a text-based app (e.g. About Text Illness Monitoring (TIM) | TIM | CDC), email, or daily phone calls.
- Requires a list of exposed people to be shared with public health.
Self-monitoring is recommended for persons who used the recommended personal protective equipment (PPE) and did not have a breach in that PPE use. Fewer exposed workers fall in this category but often include responders culling poultry.
- Exposed persons are provided with information on what symptoms to look for and who to contact if they develop any of those symptoms.
- Information can be provided using a flyer, email, or other method.
If health departments are unable to get lists of exposed persons for active monitoring, then additional monitoring strategies could be used. For example, farms can use paper screening forms to keep track of worker health. Or they may choose to use a trusted messenger who will check-in with exposed persons regularly. The goal of these strategies should still be to proactively assess the health of exposed people regularly while exposure is ongoing and for 10-days afterwards, and rapidly connect symptomatic people with public health for testing and treatment when relevant. In these alternative monitoring situations, the aggregate number of exposed people being monitored, and the number of symptomatic people identified should be reported regularly to the state or local public health jurisdiction so they know the size of the at-risk population being monitored and ensure that testing and treatment can be made available to people that become ill. State health departments report aggregate numbers of persons who are and who have been monitored to CDC weekly through the Aggregate counts of persons exposed to highly pathogenic avian influenza (HPAI) A(H5N1) virus form.
Signs and symptoms consistent with infection with HPAI A(H5N1) virus in people should be reported to appropriate health departments. Those signs and symptoms include: fever (measured) or feeling feverish/chills; cough; sore throat; difficulty breathing (shortness of breath); eye tearing; redness or irritation (conjunctivitis); headaches; runny or stuffy nose; muscle or body aches; and/or diarrhea/vomiting. Note that these signs and symptoms are non-specific and overlap with those caused by other respiratory viruses, including seasonal influenza A and B viruses. Further evaluation of symptomatic people should be performed by the state or local public health agency to assess whether testing, isolation, and/or treatment is warranted.
Specimen collection should be initiated as soon as possible once indicated. Specimens should be tested at a laboratory using the CDC RT-PCR Influenza Assay to test for HPAI. Testing and specimen collection guidance can be found at Highly Pathogenic Avian Influenza A(H5N1) Virus in Animals: Interim Recommendations for Prevention, Monitoring, and Public Health Investigations. Antiviral treatment should also be started if an exposed person becomes ill. Guidance on this treatment can be found at Interim Guidance on the Use of Antiviral Medications for Treatment of Human Infections with Novel Influenza A Viruses Associated with Severe Human Disease.