Press ReleaseFor Immediate ReleaseFriday, November 22, 2024Contact: CDC Media Relations(404) 639-3286CDC Confirms H5N1 Bird Flu Infection in a Child in California
The Centers for Disease Control and Prevention (CDC) has confirmed a human infection with avian influenza A(H5N1) (H5N1 bird flu) in a child in California. This is the first reported avian influenza H5 virus infection in a child in the United States. Consistent with previously identified human cases in the United States, the child reportedly experienced mild symptoms and received flu antivirals. There were low levels of viral material detected in the initial specimen collected, and follow-up testing of the child several days later was negative for H5 bird flu but was positive for other common respiratory viruses. The child is recovering from their illness. An investigation by the California Department of Public Health (CDPH) into the child’s possible H5N1 exposure source is ongoing.
During CDPH’s investigation, all household members reported having symptoms and specimens were collected from those people. All test results from members of the household were negative for H5 bird flu, and some family members were positive for the same common respiratory viruses as the child. Contact tracing continues, but there is currently no evidence of person-to-person spread of H5N1 bird flu from this child to others. To date, there has been no person-to-person spread identified associated with any of the H5N1 bird flu cases reported in the United States.
This case was detected through influenza testing and reported to CDPH through influenza surveillance. This is the second U.S. case identified through national surveillance. CDC continues to closely monitor available data from influenza surveillance systems, particularly in states affected by outbreaks in animals, including California, where widespread outbreaks of H5N1 bird flu have been detected in wild birds and domestic poultry since 2022 and dairy herds since August 2024 in that state.
Limited and sporadic human infections with avian influenza H5N1 virus, where animal exposure was not identified, are very uncommon but have occurred, primarily in countries other than the United States. These instances underscore the importance of ongoing surveillance and investigations at the local, state, and Federal levels.
Including this most recent case, 55 human cases of H5 bird flu have now been reported in the United States during 2024, with 29 in California.
CDC's risk assessment for the general public is low. However, people with exposure to infected or potentially infected animals, such as birds, dairy cattle, or other animals (including livestock), or to environments contaminated by infected birds or other animals, are at higher risk of infection. CDC recommends avoiding unprotected exposure to sick or dead animals, including wild birds, poultry, other domesticated birds, and other wild or domesticated animals (including cows).
CDC will continue to provide updates as additional information becomes available. For more information, read California’s statement State Reports Single, Possible Case of Bird Flu Virus in Child with Mild Symptoms.
The CDC's weekly FluView today carries the following summary of all 6 newly confirmed cases over the past week.
Six confirmed human infections with influenza A(H5) viruses were reported to CDC this week. To date, human-to-human transmission of influenza A(H5) virus has not been identified in the United States.
Five confirmed cases were reported by the California Department of Public Health. Four of these cases occurred in workers at commercial dairy cattle farms in areas where highly pathogenic avian influenza (HPAI) A(H5N1) viruses had been detected in cows, and one case occurred in a child with no known contact with influenza A(H5N1) virus-infected animals. The investigation into the source of infection for this case is ongoing, but there is currently no evidence of human-to-human transmission. There have now been 29 total confirmed human cases and one probable human case in California.
One confirmed case was reported by the Oregon Health Authority. This case was in a worker who performed depopulation activities at a commercial poultry facility where HPAI A (H5N1) viruses had been detected in birds. This is the first human case identified in Oregon.
Five of the six individuals reported this week are more than 18 years old and one was less than 18 years old. All six individuals had mild symptoms. Specimens from all six individuals were tested at state or public health laboratories using the CDC influenza A (H5) assay before being sent to CDC for further testing. Specimens from all six confirmed cases were positive for influenza A(H5) virus using diagnostic RT-PCR or genetic sequencing at CDC. Additional analysis including genetic sequencing is underway.
In response to these detections, additional case investigations and surveillance activities are being conducted by public health officials in California and Oregon.
The CSTE position statement, which includes updated case definitions for confirmed, probable, and suspect cases is available at http://www.cste.org/resource/resmgr/position_statements_files_2023/24-ID-09_Novel_Influenza_A.pdf
An up-to-date human case summary during the 2024 outbreak by state and exposure source is available at www.cdc.gov/bird-flu/situation-summary/index.html
Information about avian influenza is available at https://www.cdc.gov/flu/avianflu/index.htm.
Interim recommendations for Prevention, Monitoring, and Public Health Investigations are available at https://www.cdc.gov/bird-flu/prevention/hpai-interim-recommendations.html.
The latest case reports on avian influenza outbreaks in wild birds, commercial poultry, backyard or hobbyist flocks, and mammals in the United States are available from the USDA at https://www.aphis.usda.gov/aphis/ourfocus/animalhealth/animal-disease-information/avian/avian-influenza/2022-hpai.
if they do a test at all)
While the official CDC count has risen to 55, this does not include 4 cases confirmed by state labs but not by the CDC, nor does it include the 2nd, strongly suspected case in Missouri, or the 8 asymptomatic and/or mild cases retrospectively identified by serological testing.
These detections via serological testing strongly suggest some additional cases have gone unidentified. How many, is unknowable.
It takes more than a little luck for a community case - one w ithout known contact with livestock or someone who is known to be infected - to be picked up by surveillance. Most doctors and walk-in clinics only perform rapid flu tests (if they do a test at all), and that generally does not reveal the subtype, only if it is Influenza A positive or not.
Last year, in UK Novel Flu Surveillance: Quantifying TTD, the HKHSA described some of the challenges in detecting or confirming community spread of H5N1 - even in the UK - until after dozens, or even hundreds, of cases had occurred.While there may be a heightened index of suspicion in community with outbreaks of H5N1 in cattle or poultry, in most communities mild or moderate cases can be difficult to detect. The Missouri case was only identified a week after the patient was released from the hospital.