Aug 8, 2012 9:18 AM by CBS News
An increase in swine flu cases has the Centers for Disease Control and Prevention warning Americans to be especially careful around state and county fairs this summer.
With the fair season in full swing, health officials want attendees to avoid taking food and drinks into barns and to wash their hands after they're near animals. Pregnant women, young children, the elderly and people with weakened immune systems are especially at risk for developing the flu strain.
CDC officials say 29 human cases of the new strain of the H3N2 swine flu (dubbed H3N2v for "variant") have been confirmed in the last year, including 12 this week. Ten of the new cases were linked to the Butler County Fair in southwest Ohio, which ended last weekend.
None of the cases have been tied to human-to-human transmission and all 12 of the new patients had close contact with swine prior to getting sick. The two other new cases occurred in Hawaii and Indiana.
"While the viruses identified in these cases are genetically related, separate swine exposure events in each state are associated with infection and there is no indication that the cases in different states are related," the CDC said during a Friday press conference discussing its latest FluView Surveillance Report.
The new flu has a gene from the 2009 pandemic strain that might make it more contagious. But so far, the strain hasn't spread easily, and recent cases have been mild.
Symptoms are similar to that of other types of influenza and include fever and respiratory symptoms, such as cough and runny nose. Other possible symptoms include body aches, nausea, vomiting or diarrhea.
The CDC is collaborating with the World Health Organization on tracking H3N2.
Key Facts about Swine Influenza (Swine Flu) in Pigs
What is Swine Influenza?
Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs. Swine flu viruses do not usually infect humans, but rare human infections have occurred. (For more information about swine influenza infections in humans, see Variant Influenza Viruses in Humans). Swine flu viruses can cause high levels of illness in pig herds, but cause few deaths in pigs. Swine influenza viruses can circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans.
How many swine flu viruses are there?
Like influenza viruses in humans and other animals, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort (i.e. swap genes) and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge. Over the years, different variations of swine flu viruses have emerged. At this time, there are three main influenza type A virus subtypes that have been isolated in pigs in the United States: H1N1, H1N2, and H3N2.
How does swine flu spread among pigs?
Swine flu viruses are thought to be spread among pigs mostly through close contact and possibly from contaminated objects moving between infected and uninfected pigs. Infected swine herds, including those vaccinated against swine flu, may have sporadic disease, or may show only mild or no symptoms of infection.
What are signs of swine flu in pigs?
Signs of swine flu in pigs can include fever, depression, coughing (barking), discharge from the nose or eyes, sneezing, breathing difficulties, eye redness or inflammation, and going off feed. Some pigs infected with influenza, however, may have no symptoms at all.
How common is swine flu among pigs?
H1N1 and H3N2 swine flu viruses are endemic among pig populations in the United States and something that the industry deals with routinely. Outbreaks among pigs normally occur in colder weather months (late fall and winter) , but can occur year round. While H1N1 swine viruses have been known to circulate among pig populations since at least 1930, H3N2 influenza viruses did not begin circulating among pigs in the United States until about 1998. The H3N2 viruses initially were introduced into the pig population from humans. However, since then the H3N2 viruses circulating in pigs have changed. The H3N2 viruses circulating in pigs now are very different from the seasonal H3N2 viruses that circulate in humans.
Is there a vaccine for swine flu?
Vaccines are available to be given to pigs to prevent swine influenza illness.