Swine flu (swine influenza)
Introduction
- Swine flu (Swine influenza or pig influenza) is a viral infection caused by H1N1 type A influenza in human.
- Swine influenza is also called pig influenza, swine flu, hog flu and pig flu.
- The H1N1 swine flu virus is a human virus spread by people and not by pigs. The only way to get the new swine flu is from another person.
- The disease originally was nicknamed swine flu because the virus that causes the disease originally jumped to humans from the live pigs in which it evolved.
Causative organism
- Causative organism : H1N1 type A influenza. A H1N1 viruses that have been in circulation for many years, the CDC calls the virus “2009 H1N1 virus,” “novel H1N1” or nH1N1, “quadruple assortant H1N1,” and “2009 pandemic H1N1.
- Whereas humans primarily have α-2,6-galactose receptors for hemagglutinins and birds primarily have α-2,3-galactose receptors, swine have both types of receptors. Thus, swine hosts efficiently sustain simultaneous infection with both human and avian viruses, thereby facilitating reassortment of genetic segments between viruses of both species.
- The pandemic A/H1N1 strain of 2009–2010 was a quadruple reassortant among swine, avian, and human influenza viruses. The influenza A virus subtypes that circulate most commonly in swine are H1N1, H1N2, and H3N2.
- When a predominantly swine virus causes infections in humans, it is designated a variant virus by the addition of “v” after the subtype.
- The swine flu viruses that usually spread among pigs aren’t the same as human flu viruses. Swine flu doesn’t often infect people, and the rare human cases that have occurred in the past have mainly affected people who had direct contact with pigs. But the current “swine flu” outbreak is different. It’s caused by a new swine flu virus that has changed in ways that allow it to spread from person to person — among people who haven’t had any contact with pigs.
Mode of transmission
The H1N1 swine flu virus is a human virus spread by people and not by pigs. The only way to get the new swine flu is from another person.
The new H1N1 swine flu virus apparently spreads just like regular flu.
- You could pick up germs directly from airborne droplets from the cough or sneeze of an infected person.
- You could also pick up the virus by touching an object contaminated by the cough or touch of an infected person and then touching your eyes, mouth, or nose. That’s why you should make washing your hands a habit, even when you’re not ill. Infected people can start spreading flu germs up to a day before symptoms start, and for up to seven days after getting sick, according to the CDC.
- The H1N1 swine flu virus, like the seasonal flu virus, can become airborne if you cough or sneeze without covering your nose and mouth, sending germs into the air. Ferret studies suggest that swine flu spreads less easily by small, airborne droplets than does seasonal flu. But it does spread by this route, and it may begin to spread even more readily as the new virus fully adapts to humans.
Clinical symptoms
- Symptoms of H1N1 swine flu are like regular flu symptoms and include fever, cough, sore throat, runny nose, body aches, headache, chills, and fatigue. Many people with swine flu have had diarrhea and vomiting.
- Like seasonal flu, pandemic swine flu can cause neurologic symptoms in children. These events are rare, but, as cases associated with seasonal flu have shown, they can be very severe and often fatal. Symptoms include seizures or changes in mental status (confusion or sudden cognitive or behavioral changes). It’s not clear why these symptoms occur, although they may be caused by Reye’s syndrome. Reye’s syndrome usually occurs in children with a viral illness who have taken aspirin — something that should always be avoided.
Severity
- The severity of cases in the current swine flu outbreak has varied widely, from mild cases to fatalities.
Diagnosis
- Clinical symptoms are nonspecific; can also be caused by many other conditions. That means that you and your doctor can’t know, just based on your symptoms, if you’ve got swine flu.
- Only lab tests can definitively show whether you’ve got swine flu. State health departments can do these tests. During the peak of the pandemic, these tests were reserved for patients with severe flu symptoms.
Treatment
Specific antiviral therapy is available for influenza. Influenza A infections can be treated by following drugs :
- Neuraminidase inhibitors – Zanamivir (Relenza), Oseltamivir (Tamiflu), Peramivir (Rapivab)
Pandemic H1N1 swine flu virus is sensitive to the antiviral drugs Tamiflu and Relenza. These antiviral drugs are most effective when taken within 48 hours of the start of flu symptoms. It’s resistant to older flu drugs.
A third antiviral drug, peramivir, can be used only in hospitalized patients with severe flu. Peramivir is an intravenous drug approved for use under the FDA’s Emergency Use Authorization.
Prevention
The CDC recommends taking these steps to prevent Swine flu:
- Wash your hands regularly with soap and water, especially after coughing or sneezing. Scrub for at least 20 seconds and rinse thoroughly.
- If soap and water are not available, wash your hands with an alcohol-based hand gel. Rub your hands together until the alcohol dries completely.
- Avoid close contact — that is, being within 6 feet — with people who have flu-like symptoms.
- Avoid touching your mouth, nose, or eyes. That’s not easy to do, so keep those hands clean.
- If you have flu-like symptoms — fever plus at least cough or sore throat or other flu symptoms — stay home for seven days after symptoms begin or until you’ve been symptom-free for 24 hours — whichever is longer.
- Wear a face mask (consider using an N95 respirator) if you must come into close contact with a sick person.
- “Close contact” means within 6 feet. Note: There is no definitive proof that a face mask prevents flu transmission. Do not rely solely on a face mask to prevent infection.
- Wear an N95 respirator if helping a sick person with a nebulizer, inhaler, or other respiratory treatment. Note:
- There is no definitive proof that a respirator prevents flu transmission. Do not rely solely on a respirator to prevent infection.
- People who have or are suspected of having swine flu should wear a face mask, if available and tolerable, when sharing common spaces with other household members, when outside the home, or when near children or infants.
- Breastfeeding mothers with swine flu symptoms should express their breast milk, and the child should be fed by someone else.
