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
sinceāÆMarchāÆ2024.āÆIn 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. ā
āāRecommendations for Healthcare āProviders
āāConsider Avian Influenza Infection
Healthcare providers should consider the possibility of avian influenza A virus infection in a patient with:
Signs and symptoms consistent with
acute respiratory tract infection
and/or
conjunctivitis;*
AND
A
history ofāÆexposureāÆin the last 10 daysāÆto animals suspected or confirmed to have avian
influenza A, or
who have had
exposure to
raw milk.āÆ
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.
āSpecimen Collection āand Testing
āHealthcare providers who suspect avianāÆinfluenza AāÆvirus 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 deteāct influenza A, but hemagglutinin subtyping must be done to detect avian influenza A virus (or rule it out by detecting H3 or H1 influenza A) in an influenza A positive specimen.āÆāÆ
āWhen concern for detecting avian influenza A 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).
āCommercial 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 avian influenza A (e.g., symptomatic people with limited animal exposure, or no known exposure to infected animals or humans).ā
āāāāTesting at a commercial laboratory offering testing for avian influenza A H5 subtyping can also be ordered for low suspicion patients.
āāSpecimens should ideally be collected within 24ā72 hours of symptom onset and no later than 10 days after symptom onset.āÆāāāāā
āRespiratory specimens for submission to a public health laboratory*
āSeparate oropharyngeal and anterior nares swabs are preferred (combining both swabs into a single transport media tube is also acceptable).
Nasopharyngeal swabs are acceptable, but to date have had a lower yield for positive test results in cases than oropharyngeal or anterior nares swabs.āÆ
āA conjunctival swab should also be collected from anyone experiencing conjunctivitis, and has the highest yield for detection in cases to date.
āāāIf 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 anterior nares 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 for enteric pathogens,
as well as testing for influenza A if it becomes available. āā
Specimens should be collected using swabs with synthetic tips (e.g., polyester or DacronĀ®) and an aluminum or plastic shaft.āÆ
āāSwabs should be placed in specimen collection vialsāÆcontainingāÆ2ā3ml of viral transport media (VTM) or universal transport media (UTM).āÆ
āSpecimens 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 DiseaseāÆLaboratoryāÆ(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
āTreatment
āAntiviral treatment is recommended as soon as possible for patientsāÆwith suspected or confirmedāÆinfluenza A(H5N1) virus infection.āÆāÆAntiviral treatment should not be delayed while waiting for laboratory test results.āÆ
The standardāÆtreatmentāÆdose of oseltamivir is 75 mg twice daily for 5 days for adults.āÆ
āDosage adjustment is needed for children, infants, neonates and for adult patients withāÆrenal impairment.
āOseltamivir is not recommended for people with end-stage renal disease who are not receiving dialysis.āÆ
Pending further data, longer courses of treatment (e.g., 10 days) should be considered for severely ill hospitalized patients with novel influenza A virus infections. For additional information, please see the
Emergency Use Instructions (EUI) Fact Sheet for Healthcare Providers.
Chemoprophylaxis
āChemoprophylaxis dosing for avian influenza A 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.
āāāProphylaxis 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.
āāConsideration 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 ināfluenzaā. ā
Healthcare Infection Prevention and āāControl
āāIf 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:
āUse diligent hand hygiene before and after contact with the patient.
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.