Swine influenza (also called swine flu, hog flu, and pig flu) refers to influenza caused by those strains of influenza virus, called swine influenza virus (SIV), that usually infect pigs. Swine influenza is common in pigs in the mid western United States (and occasionally in other states), Mexico, Canada, South America, Europe (including the United Kingdom, Sweden, and Italy), Kenya, Mainland China, Taiwan, Japan and other parts of eastern Asia.
Transmission of swine influenza virus from pigs to humans is not common. When transmitted, the virus does not always cause human influenza and often the only sign of infection is the presence of antibodies in the blood, detectable only by laboratory tests. People who work with pigs, especially people with intense exposures, are at risk of catching swine flu. However, only about fifty such transmissions have been recorded since the mid-20th century, when identification of influenza subtypes became possible. Rarely, these strains of swine flu can pass from human to human. In humans, the symptoms of swine flu are similar to those of influenza and of influenza-like illness in general, namely chills, fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort.
Image courtesy of CDC/ Cynthia Goldsmith
2009 Outbreak of Influenza A(H1N1) virus
The 2009 outbreak of influenza A (H1N1) virus was an epidemic of a new strain of influenza virus identified in April 2009, and is commonly referred to as “swine flu.”The source of the outbreak in humans is still unknown but cases were first discovered in the U.S. and officials soon suspected a link between this and an earlier outbreak of late-season flu cases in Mexico. Within days, hundreds more suspected cases, many resulting in death, were discovered in Mexico, with more cases found in the U.S. and several other countries. Soon after, the U.N.’s World Health Organization (WHO), along with the U.S. Centers for Disease Control and Prevention (CDC), became concerned that it could become a worldwide flu pandemic, and WHO then raised its pandemic alert level to “Phase 5″ out of 6 maximum, as a”signal that a pandemic is imminent”.
Symptoms and Severity
The symptoms seen in U.S. cases resemble those normally seen in influenza, with fever, cough, sore throat, runny nose, headache, and muscle soreness. However, about 38% of patients had vomiting or diarrhea, which is unusual in infections with other strains of influenza. The incubation period between infection and the appearance of symptoms is about two to seven days.
Real time reverse transcription polymerase chain reaction should be used as the method of choice for detecting H1N1.
Antiviral drugs can be used to alleviate the situation. They improve the condition of the patient. Oseltamivir and Zanamivir are recommended for this purpose. Besides, supportive therapy should be applied (for fever, dehydration, pain). Most patients make a full recovery without any medical therapy.
Swine flu vaccine is available recommended by FDA. Besides methods should be adopted to limit spread of infection from pigs to humans (highly unlikely in our society) and from person to person, by means of droplet infection (by coughing, sneezing).