āSituational Update
Hāāuman Cases
As of December 6, 2024,āÆthe California Department of Public Health has received reports of 32 confirmed and 1 probable case of influenza A(H5N1) infection.āÆAll but one case has been among workers at dairy farms with infected cows; all infected dairy workers had mild illness with conjunctivitis as a prominent symptom. One case occurred in a child with mild respiratory symptoms and no known animal exposure. Nationally, 58 confirmed cases have been detected; all but two cases were in poultry or dairy workers.
The risk to the general publicāÆremainsāÆlow. However, people with job-related or recreational close and prolonged exposures to infected birds, cows, or other animals are at higher risk of infection.āÆāÆ ā
Animal Cases
As of December 6, 2024, avian influenza AāÆhas been detected in over 700 U.S. dairy herds in 15 states since March 2024. In California, 504 dairy herds have been infected since August 2024. Recently, the first raw dairy farm was infected leading to recall of their unpasteurized raw milk products.
Since the start of the outbreak in February 2022, avian influenza A has been detected in 1,264 commercial and backyard poultry flocks in 49 states. In California, 76 infected commercial and 32 backyard flocks have been infected. āā
Recommendations
Consider Avian Influenza Infection
āāIf youāÆencounterāÆpatients who work with infected animals, please encourage them toāÆuse āpersonal protective equipment (PPE)āÆand suggest they receive seasonal influenza vaccine during influenza season.āÆ
*If exposure was consumption of raw dairy products, and only gastrointestinal symptoms are present, interim recommendations are to test as below. ā
āSpecimen CollectionāÆand TestingāÆ
āāāāHealthcare providers who suspectāÆinfluenza A (H5N1)āÆvirus infection shouldāÆimmediatelyāÆreach out toāÆtheirāÆlocal health department (LHD).āÆThe LHDāÆcanāÆhelpāÆdetermineāÆif testing isāÆwarranted, recommend appropriate specimens to collect based on symptomatology,āÆand coordinate testing at a public health or commercial laboratory that can perform H5 subtyping (if appropriate).*āÆ
Influenza testing at clinical orāÆcommercial laboratories can detect influenza A, but hemagglutinin subtyping must be done to detect influenza A(H5N1) virus (or rule it out by detecting H3 or H1 influenza A) in an influenza A positive specimen.āÆāÆ
When concern for detecting influenza A(H5N1) infection is high, testing should be sent to a public health laboratory for timely public health response ( e.g., symptomatic farm workers exposed to infected animals or symptomatic persons exposed to a confirmed human case).
Commercial PCR tests for influenza can be used to rule out influenza A (and therefore H5N1) infection in symptomatic people less likely to be infected with influenza A(H5N1) (e.g., symptomatic people with limited animal exposure, or no known exposure to infected animals or humans).
āāāSpecimens should ideally be collected within 24ā72 hours of symptom onset and no later than 10 days after symptom onset.āÆāāāāā
Respiratory specimens for submission to a public health laboratory*
Separate oropharyngeal and nasal swabs are preferred (combining both swabs into a single transport media tube is acceptable).
Nasopharyngeal swabs are acceptable, but to date have had a lower yield for positive test results in cases than oropharyngeal or nasal swabs.āÆ
āA conjunctival swab should also be collected from anyone experiencing conjunctivitis, and has the highest yield for detection in cases to date.
If both eyes are affected, each eye should be swabbed with a separate swab but both swabs should be placed in a single transport media tube.
Conjunctival swabsāÆMUSTāÆbe paired with oropharyngeal and nasal swab specimens or a nasopharyngeal swab specimen, even if the person does not have respiratory symptoms.āÆ
āIf the symptomatic person consumed raw dairy products and has gastrointestinal symptoms (with or without respiratory symptoms), stool should also be collected, if possible, and held for potential testing.
Specimens should be collected using swabs with synthetic tips (e.g., polyester or DacronĀ®) and an aluminum or plastic shaft.āÆ
āāāāSwabs should be placed in specimen collection vialsāÆcontainingāÆ2ā3ml of viral transport media (VTM) or universal transport media (UTM).āÆ
Specimens should be refrigerated or frozen after collection. Refrigerated specimens should be transported to the public health lab on cold packs. Frozen specimens should be transported on dry ice.āÆ
For further information about laboratory testing for influenza A(H5), please contact the laboratory that will be conducting testing as specific requirements for acceptable specimens at each laboratory vary.
For further information about laboratory testing for influenza A(H5) at the CDPH state laboratory, please refer to the CDPHāÆViral and Rickettsial DiseasesāÆLaboratoryāÆ(VRDL) website, email questions to VRDL.submittal@cdph.ca.gov,āÆor call the VRDL at 510-307-8585 (M-F, 9am ā 5pm Pacific Time, excluding holidays).āÆā
*Commercial laboratories may have differenāt specimen submission recommendations for H5 subtyping than public health laboratories. ā
Chemoprophylaxis
āChemoprophylaxis dosing for influenza A (H5N1) is the same as treatment dosing: 75 mg twice daily for adults for 5 days if there has been a time-limited exposure OR 10 days if exposure is ongoing.
Prophylaxis is recommended for household contacts of confirmed cases and can be considered in workers to infected or potentially infected cows who have had an unprotected discrete high-risk exposure such as a milk splash to the eye.
Consideration for prophylaxis should be based on clinical and public health considerations such as type and duration of exposure, time-course, infection status of animal or human exposure and if person is at increased risk for complications with seasonal influenzaā.
āHealthcare Infection Prevention and Control
If a case is suspected, immediately mask the patient and place them in an airborne infection isolation room (AIIR) with the door closed. While in an AIIR, the patientās mask may be removed.
If an AIIR is not available, place the patient in a single-patient room with the door closed and have the patient remain masked.
Use personal protective equipment that includes:
Use diligent hand hygiene before and after contact with the patient. ā
Limit room entry to essential personnel. Limit transport of patient outside their room.
If a non-AIIR room is used, after the patient leaves, the room should not be reused and unprotected individuals should not enter until sufficient time has elapsed for enough air changes to remove potentially infectious particles, per CDC guidance. For example, in a patient-care area with 6 air exchanges per hour, the time to removal of airborne contaminants with 99.9% efficiency is 69 minutes.
For additional infection control recommendations, see CDC Interim Guidance for Infection Control Within Healthcare Settings When Caring for Confirmed Cases, Probable Cases, and Cases Under Investigation for Infection with Novel Influenza A Viruses Associated with Severe Disease. ā
For applicable Cal/OSHA requirements in healthcare settings, please see Californiaās Aerosol Transmissible Diseases standard.āÆ
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