Flu Virus binding to Receptor Cells – Credit CDC
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Today's weekly FluView surveillance report contains an update on the Texas H5N1 case first reported 5 days ago (see CDC Statement & Risk Assessment On The Texas H5N1 Case), which provides more details on the timeline, as well as confirming that no additional cases have been detected.
Novel Influenza A Virus:
A human infection with highly pathogenic avian influenza (HPAI) A(H5N1) virus was reported by the Texas Department of State Health Services and confirmed by CDC on March 30, 2024.
A patient aged >18 years in Texas developed conjunctivitis on approximately March 27, 2024, while working at a commercial dairy cattle farm. HPAI A(H5N1) virus has been recently detected in dairy cattle, poultry and wild birds in Texas. Respiratory and conjunctival specimens were collected on March 28, 2024, and tested at the Texas Tech University Bioterrorism Response Laboratory that same day. RT-PCR analysis indicated that both specimens were presumptive positive for influenza A(H5) virus. The specimens were then sent to CDC for further testing. They were received and tested at CDC on March 30, 2024, and confirmed as HPAI A(H5N1) virus clade 2.3.4.4b using diagnostic RT-PCR and sequencing. The patient did not report symptoms other than conjunctivitis, was not hospitalized, and is recovering. Starting on March 29, 2024, the patient was recommended to isolate and was provided with influenza antivirals per CDC guidance (https://www.cdc.gov/flu/avianflu/clinicians-evaluating-patients.htm).
Public health officials are conducting surveillance activities in the area in response to this detection. Household contacts of the patient have not reported illness and have been provided influenza antiviral prophylaxis in accordance with CDC recommendations. No additional cases of human infection with HPAI A(H5N1) associated with this case and no human-to-human transmission of HPAI A(H5N1) virus have been identified.
This is the second person to test positive for HPAI A(H5N1) virus in the United States. The first was reported in April 2022 in Colorado.
Currently in the United States, HPAI A(H5N1) virus detections among wild birds are widespread, there are sporadic outbreaks among poultry and backyard flocks, and sporadic infections in wild mammals have been reported by United States Department of Agriculture (USDA) Animal Plant Health Inspection Service (APHIS). On March 25, USDA reported the first detections of H5N1 in dairy cattle in Texas and Kansas. Since then, additional detections in dairy cattle have been reported from Idaho, Michigan, New Mexico, and Ohio. USDA is continuing to monitor and test samples collected from other farms where cattle are displaying similar symptoms.
CDC recommends that state and local public health departments monitor people who were exposed to birds or other animals (including livestock) suspected to be infected with avian influenza viruses for onset of signs and symptoms until 10 days after their last exposure and that people who develop signs or symptoms of respiratory illness and/or conjunctivitis be tested for influenza. During February 9, 2022 — March 29, 2024, over 8,000 people were actively monitored following HPAI exposure.
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/flu/avianflu/hpai/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.
Additional information regarding human infections with novel influenza A viruses:
Surveillance Methods | FluView Interactive
Today's FluView also reports that while influenza activity remains elevated, it is decreasing nationally (see chart below).
This is good news because the less seasonal influenza in circulation - the lower the chances are that someone could be infected with both seasonal flu and HPAI H5N1 - which could conceivably lead to the creation of a reassortant virus (see The `Other Mixing Vessel' For Pandemic Influenza).
