This is an official CDC HEALTH NOTICE
***Missouri healthcare providers in the City of St. Louis, please contact the City of St. Louis Health Department or the Office of Communicable Disease Prevention and Control of the St. Louis Department of Health and Senior Services. Missouri (DHSS) at 573-751-6113 or 800-392-0272 (24/7) for questions about this CDC Health Notice, to report a case of influenza in a patient with recent exposure to swine, or to request an additional subtype-specific real-time polymerase chain reaction (RT-PCR) of influenza isolates at the Missouri State Public Health Laboratory.***
The Centers for Disease Control and Prevention (CDC) is issuing this Health Alert Network (HAN) health advisory to provide updates on recent variants of infections by influenza virus⸣ and summarize CDC recommendations for the identification, treatment, and prevention of variant influenza virus infection for the summer and fall of 2022.
In August 2022, five cases of human infection with influenza viruses that generally spread only in pigs, also known as variant influenza virus infections, were reported to CDC. These cases include three influenza A(H3N2) variant (A(H3N2)v) infections and two influenza A(H1N2)v virus infections. These cases were identified in West Virginia (3), Oregon (1), and Ohio (1). Four of the five cases reported exposure to pigs or attendance at an agricultural fair prior to illness, and one reported no contact with pigs or attendance at an agricultural fair prior to illness. The clinical features of these cases have been similar to those of seasonal influenza infections and have included fever, cough, pharyngitis, myalgia, and headache. There have been no hospitalizations or deaths among these five cases, and all patients are recovering or have recovered from their illnesses. To date, no person-to-person spread associated with the five recent influenza virus variants has been identified.
Early identification and investigation of variant influenza virus infections are important to determine if the virus is spreading efficiently between people. Rapid detection and characterization of new influenza A viruses and efforts to reduce transmission to others remain important components of national efforts to prevent the emergence of new viruses that could have pandemic potential. To achieve this, testing for influenza viruses and monitoring for new influenza A virus infections, including variant influenza virus infection, should continue throughout the year.
People, especially those at higher risk for complications from influenza, can take public health measures to limit their risk of infection (eg, limit exposure to infected animals). Clinicians are encouraged to consider variant influenza virus infection as a possible diagnosis when evaluating patients with acute respiratory illness and pre-illness exposure to pigs or agricultural fairs.
Since 2005, 504 variant influenza virus infections (of different influenza A virus subtypes) have been identified in the United States; most of these infections have been associated with exposure to pigs or attendance at an agricultural fair prior to illness onset. Agricultural fairs occur in the United States each year, primarily during the summer and early fall. Many fairs have pig barns, where pigs from different geographical locations come into close contact with each other and with people. These places can allow influenza viruses to spread between pigs and between pigs and people. Infected pigs can shed influenza viruses even if they are not symptomatic (eg, coughing or sneezing).
CDC anticipates that state health departments may identify more cases of infection with variant influenza viruses in 2022 as the agricultural fair season continues. Testing for variant influenza viruses should focus primarily on persons with exposures known to be associated with variant influenza virus infection (eg, attendees of agricultural fairs or workers in the swine industry) . New influenza A virus infections, including those caused by variant influenza viruses, are notifiable conditions in the United States, and all confirmed cases must be reported to CDC within 24 hours.
Recommendations for doctors
Outside of the traditional influenza season, ask patients with suspected influenza if they have recently been exposed to pigs. Clinicians who suspect influenza in people with recent exposure to swine should: Obtain a nasopharyngeal swab or aspirate from the patient, Place the swab or aspirate in viral transport medium, and Contact their state or local health department to arrange transport and request a timely diagnosis. in a state public health laboratory. Recommend antiviral treatment in patients with suspected or confirmed variant influenza virus infection who are hospitalized, have severe illness, or are in a group considered to be at higher risk for complications from influenza². Antiviral treatment may also be considered for those who are not at increased risk based on clinical judgment and if treatment can be started within 48 hours of illness onset.
Recommendations for Departments of Public Health and Laboratories
Enhance respiratory disease surveillance during the agricultural fair season to facilitate timely case detection and investigation of variant influenza viruses. Respiratory specimens from persons suspected of having a variant influenza A virus should be collected and submitted for subtype-specific real-time polymerase chain reaction (RT-PCR) testing at a public health laboratory state. Although commercially available rapid influenza diagnostic tests (RIDTs) and molecular assays for influenza can reliably detect variant influenza A viruses, they cannot differentiate between variants. of influenza A viruses of human influenza A viruses. Public health laboratories should immediately submit influenza A virus specimens that cannot be subtyped or that are presumptively positive for variant influenza (using the methods described in the assay Instructions for Use) to CDC and submit all unusual samples as soon as possible after identification. Email fl[email protected] to alert CDC that you have a sample to submit.
Recommendations for the public
People who are at higher risk for complications from influenza² should avoid exposure to pigs and pig barns at fairs this year. If you cannot avoid exposure to pigs, you should wear a well-fitting mask that covers your nose and mouth and wash your hands frequently. All people should take precautions when participating in activities that may involve contact with pigs. Precautions include hand hygiene before and after exposure to animals, avoiding eating or drinking in animal areas, and avoiding close contact with animals that appear or act ill. Patients with influenza-like illness who are at increased risk for complications from influenza² should consult their health care provider as soon as possible after the onset of symptoms to determine if treatment with antiviral medications is warranted. Patients experiencing influenza-like symptoms after direct or close contact with pigs and seeking medical attention should notify their health care provider of the exposure.
For more information
⸣Influenza viruses that circulate in pigs are called swine influenza viruses when isolated from pigs, but are called variant viruses when isolated from humans.
²This includes people with certain underlying chronic medical conditions, such as asthma, diabetes, heart disease, or neurological conditions, people who are pregnant, and people ages 5 and under and 65 and over, or who have weakened immune systems.