SwiNe inLuEnZa

What is swine influenza?

Swine influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus. Swine flu viruses cause high levels of illness and low death rates among pigs. Swine influenza viruses may circulate in swine, including swine in Illinois.

How common is swine flu among pigs?

Outbreaks among pigs normally occur in late fall and winter and sometimes with the introduction of new pigs into herds. In the United States, studies have shown that 30 percent to 51 percent of the pig population has antibody evidence of having had H1N1 infection. Antibody can be due to vaccination of pigs for swine flu or from natural infection with swine flu. There is currently no way to differentiate antibody produced in response to vaccination in pigs from antibody made in response to natural infection with H1N1.

Can humans catch swine flu?

Swine flu viruses do not normally infect humans. However, rare human infections with swine flu have occurred. In the past several years, CDC has received, on average, about one influenza virus isolate from a human that tests positive for swine flu each year. Most commonly, these cases occur in persons with direct exposure to pigs. In addition, there have been rare documented cases of one person spreading swine flu to others. For example, an outbreak of apparent swine flu infection in pigs in Wisconsin in 1988 resulted in multiple human infections, and, although no community outbreak resulted, there was antibody evidence of virus transmission from the patient to health care workers who had close contact with the patient.

How does swine flu spread?

Pigs infected with influenza virus have a runny nose, lethargy, cough and decreased appetite. The virus likely spreads from pig to pig through contact with infected mucous secretions. (When pigs are really sick, their mucous carries high levels of virus). Strains of swine flu virus also can be directly transmissible to humans. Most human infections occurred following direct contact with infected pigs. However, there has been at least one documented case of human-to-human transmission of swine flu.

Is there a vaccine for swine flu?

Commercial vaccines are available in Europe and North America. Results from various studies show that vaccinated animal exposed to swine influenza virus have markedly reduced nasal shedding, virus infection in lung tissue, and lung pathology compared to non-vaccinated animals. Studies have also shown than maternally derived antibody in vaccinated sows protected 5 week old pigs from clinical disease, virus infection in the lung, and lung pathology but did not prevent nasal viral shedding.