The Centers for Disease Control and Prevention (CDC) has identified 18 cases of new swine flu viruses in Ohio and Michigan state fair attendees, highlighting the need for precaution when handling pigs.
Local agricultural fairs offer a family-friendly outing to celebrate regional farmers, but exposure to farm animals at these fairs can also create an avenue leading to illness. The Centers for Disease Control and Prevention (CDC) recently identified a new type of swine flu in people in two states, which they’ve linked back to state fair attendance.
The CDC’s Morbidity and Mortality Weekly Report (MMWR) offers a weekly roundup of news on public health from the agency. Their report for the week of October 28th details findings from their investigation of 18 swine flu cases contracted in July and August, which were first reported to the CDC by the Ohio Department of Health Laboratory and the Michigan Department of Health and Human Services Laboratory. A respiratory specimen from a 13-year-old boy in Ohio taken in late July was tested using real-time reverse transcription—polymerase chain reaction (RT-PCR) and came up positive for an influenza A (H3N2) variant, a swine flu that typically infects swine populations and occasionally causes illness in humans. Soon after, Michigan health officials reported finding the same H3N2 variant in a 9-year-old child. Both cases were linked to visits to local agricultural fairs, where the children came into contact with pig exhibits believed to have transmitted the swine flu. By August 25th, health officials identified and reported a total of 18 cases resulting from two H3N2 variant viruses. Of those infected, 13 people had come in direct contact with pigs through touching or handling, while five had only indirect contact such as passing through a barn. Of those who fell ill, 16 were children, seven of whom were under the age of 5. One person was hospitalized, and all had full recoveries.
Symptoms of swine flu are similar to the human seasonal flu, including fever, coughing, and sore throat. The largest known outbreak of an H3N2 variant virus occurred in 2012, though there were only 343 reported cases from 2011 to 2014. Swine flu does not typically infect humans, but the virus is more likely to spread from human-to-human when it undergoes genetic reassortment, which consists of combining genes of viruses from different species. In the recent 18 cases reported in Ohio and Michigan, the CDC identified 16 reassortments of swine and human viruses in a combination of genes that had not been previously found in H3N2 variants infecting humans. The report notes that the hemagglutinin gene found in the swine flu virus is a human gene likely introduced to swine in 2010 or 2011, and that this new reassortment has likely been circulating and evolving in pig populations since then, making the recently discovered virus genetically and antigenically different from the H3N2 virus currently circulating and causing seasonal illness.
“Influenza viruses are constantly evolving and are unpredictable so we cannot say with certainty that we will detect this same virus in humans again,” said Rebekah Stewart Schicker, MSN, MPH, Epidemic Intelligence Service Officer at the CDC, noting that variant viruses can also come from swine that people keep on their property. “However, our previous experience tells us that new variant viruses usually circulate for more than one year so it is likely that we will see this virus emerge again in the following years.” Schicker noted that the CDC continually tracks influenza activity through surveillance with public health and clinical laboratories, outpatient healthcare providers, hospitals, state health departments, and other agencies.
The recent cases underscore the importance of taking precautionary measures around swine and their environments to prevent such influenza outbreaks. The new MMWR report emphasizes that agricultural fair organizers should take preventive steps to protect the public, including limiting the time that swine are on the fairgrounds, keeping ill swine isolated, having an on-call veterinarian, offering handwashing stations, and prohibiting food and beverages in animal barns. For people who may come in contact with swine, the CDC recommends the following safety measures:
For People with High Risk Factors:
For People Not at High Risk: