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Swine influenza
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Overview
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 cause high levels of illness and low death rates in pigs. Swine influenza viruses may circulate among swine throughout the year, but most outbreaks occur during the late fall and winter months similar to outbreaks in humans. The classical swine flu virus (an influenza type A H1N1 virus) was first isolated from a pig in 1930.
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Swine influenza viruses are most commonly of the H1N1 subtype, but other subtypes are also circulating in pigs (e.g., H1N2, H3N1, H3N2). Pigs can also be infected with avian influenza viruses and human seasonal influenza viruses as well as swine influenza viruses. The H3N2 swine virus was thought to have been originally introduced into pigs by humans. Sometimes pigs can be infected with more than one virus type at a time, which can allow the genes from these viruses to mix. This can result in an influenza virus containing genes from a number of sources, called a "reassortant" virus. Although swine influenza viruses are normally species specific and only infect pigs, they do sometimes cross the species barrier to cause disease in humans.
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Causes
The strain of influenza virus recently identified in Mexico and USA is unique because it is a combination of genes from swine, bird, and human influenza viruses.
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Spread of this swine influenza A (H1N1) virus is thought to be happening in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose.
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Epidemiology
The disease is considered endemic in the United States. Outbreaks in pigs are also known to have occurred in North America, South America, Europe (including the UK, Sweden, and Italy), Africa (Kenya), and in parts of eastern Asia including China and Japan.
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Current Situation The United States Government has reported seven confirmed human cases of Swine Influenza A/H1N1 in the USA (five in California and two in Texas) and nine suspect cases. All seven confirmed cases had mild Influenza-Like Illness (ILI), with only one requiring brief hospitalization. No deaths have been reported. The Government of Mexico has reported three separate events. In the Federal District of Mexico, surveillance began picking up cases of ILI starting 18 March. The number of cases has risen steadily through April and as of 23 April there are now more than 854 cases of pneumonia from the capital. Of those, 59 have died. In San Luis Potosi, in central Mexico, 24 cases of ILI, with three deaths, have been reported. And from Mexicali, near the border with the United States, four cases of ILI, with no deaths, have been reported.
Of the Mexican cases, 18 have been laboratory confirmed in Canada as Swine Influenza A/H1N1, while 12 of those are genetically identical to the Swine Influenza A/H1N1 viruses from California. The majority of these cases have occurred in otherwise healthy young adults. Influenza normally affects the very young and the very old, but these age groups have not been heavily affected in Mexico.
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Prevention
Preventive measures include: 1. Avoid close contact.
Avoid close contact with people who are sick. When you are sick, keep your distance from others to protect them from getting sick too.
2. Stay home when you are sick.
If possible, stay home from work, school, and errands when you are sick. You will help prevent others from catching your illness.
3. Cover your mouth and nose.
Cover your mouth and nose with a tissue when coughing or sneezing. It may prevent those around you from getting sick.
4. Clean your hands.
Washing your hands often will help protect you from germs.
5. Avoid touching your eyes, nose or mouth.
Germs are often spread when a person touches something that is contaminated with germs and then touches his or her eyes, nose, or mouth.
6. Practice other good health habits.
Get plenty of sleep, be physically active, manage your stress, drink plenty of fluids, and eat nutritious food.
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Advice for Travellers Recommendations for travellers 1. Wash your hands
By washing your hands with soap under warm running water, you will reduce your chance of getting the flu.
Alcohol-based hand gel can also be used if soap and water are not readily available. It's a good idea to keep some with you in your pocket or purse when you travel.
2. Practice proper cough and sneeze etiquette
Cover your mouth and/or nose to reduce the spread of germs. Remember to wash your hands afterwards.
3. Try to avoid close contact with sick people
Cover your mouth and nose to reduce the spread of germs. Remember to wash your hands afterwards.
4. Monitor your health
If you develop flu-like symptoms when you return, you should see a seek medical attention immediately
Inform the health care provider who sees you, if you have been travelling to areas affected with Swine flu such as Mexico, California and Texas. (Details) | Prepare for your trip before you leave
- Visit CDC's Travelers' Health Website or your local governmental health website to learn about any disease risks and CDC health recommendations for areas you plan to visit.
- See a travel medicine specialist or a doctor familiar with travel medicine at least 46 weeks before you leave to answer your questions and make specific recommendations for you.
- Antiviral Medications: Travelers from the US going to Mexico that are at high risk of severe illness from influenza (for example persons with chronic conditions such as diabetes, lung disease, heart disease, and the elderly) are recommended to take antiviral medications for prevention of swine influenza during travel. The recommended antiviral drugs for swine influenza are oseltamivir (brand name Tamiflu) and zanamivir (brand name Relenza). Both are prescription drugs that fight against swine flu by keeping flu viruses from reproducing in your body. These drugs can prevent infection if taken as a preventative. Talk to your doctor about correct indications for using influenza antiviral medications. Always seek medical care if you are severely ill.
- Antiviral chemoprophylaxis (pre-exposure or post-exposure) is recommended for the following individuals:
1. Household close contacts who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly) of a confirmed or suspected case.
2. School children who are at high-risk for complications of influenza (persons with certain chronic medical conditions) who had close contact (face-to-face) with a confirmed or suspected case.
3. Travelers to Mexico who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly).
4. Border workers (Mexico) who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly).
5. Health care workers or public health workers who had unprotected close contact with an ill confirmed case of swine influenza A (H1N1) virus infection during the case's infectious period.
- Antiviral chemoprophylaxis can be considered for the following:
1. Any health care worker who is at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly) who is working in an area with confirmed swine influenza A (H1N1) cases, and who is caring for patients with any acute febrile respiratory illness.
2. Non-high risk persons who are travelers to Mexico, first responders, or border workers who are working in areas with confirmed cases of swine influenza A (H1N1) virus infection.
- Be sure you are up-to-date with all your routine vaccinations, including seasonal influenza vaccine if available.
- Pack a travel health kit that contains basic first aid and medical supplies. See Pack Smart in Your Survival Guide to Safe and Healthy Travel for a list of what to include in your travel health kit.
- Identify the health-care resources in the area(s) you will be visiting.
- Check if your health insurance plan will cover you abroad. Consider purchasing additional insurance that covers medical evacuation in case you become sick.
During your visit to an area affected by swine flu:
Monitor the local situation
- Pay attention to announcements from the local government.
- Follow local public health guidelines, including any movement restrictions and prevention recommendations.
Practice healthy habits to help stop the spread of germs
- Wash your hands often with soap and water. This removes germs from your skin and helps prevent diseases from spreading.
- Use waterless alcohol-based hand gels (containing at least 60% alcohol) when soap is not available and hands are not visibly dirty.
- Cover your mouth and nose with a tissue when you cough or sneeze and put your used tissue in a wastebasket.
- If you don't have a tissue, cough or sneeze into your upper sleeve, not your hands.
- Wash your hands after coughing or sneezing, using soap and water or an alcohol-based hand gel.
- Follow all local health recommendations. For example, you may be asked to put on a surgical mask to protect others.
Seek medical care if you feel sick
- If you are ill with fever and other symptoms of swine flu like cough and sore throat, see a doctor, especially if you think you may have had contact with someone with swine flu or severe respiratory illness in the past 7 days before becoming ill.
- You should avoid further travel until you are free of symptoms, unless traveling locally for medical care.
After you return from Mexico
- Closely monitor your health for 7 days
- If you become ill with fever and other symptoms of swine flu like cough and sore throat and possibly vomiting and diarrhea during this period, call your doctor or clinic for an appointment right away. Your doctor may test you for influenza and decide whether influenza antiviral treatment is indicated.
- When you make the appointment, tell the doctor the following: Your symptoms, Where you traveled, and If you have had close contact with a person infected with swine flu.
- Avoid leaving your home while sick except to get local medical care, or as instructed by your doctor. Do not go to work or school while ill. If you must leave your home (for example, to seek medical care) wear a surgical mask to keep from spreading your illness to others.
- Always cover your nose and mouth with a tissue when you cough or sneeze. Throw away used tissues in a trash can.
- Wash your hands with soap and water often and especially after you cough or sneeze. If soap and water are not available, use an alcohol-based hand gel containing at least 60% alcohol.
- Avoid close contact with other people as much as possible.
- Wear a surgical mask if you are in contact with other people.(Close)
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Symptoms
Usually include symptoms similar to season influenza (flu) including:- headache, chills and cough followed by fever, loss of appetite, muscle aches and fatigue, runny nose, sneezing, watery eyes and throat irritation.
- Nausea, vomiting and diarrhea may occur in adults as well as in children.
- In more severe cases, or in people with chronic conditions, complications such as pneumonia may develop.
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Complications
It is likely that most of people, especially those who do not have regular contact with pigs, do not have immunity to swine influenza viruses that can prevent the virus infection. If a swine virus establishes efficient human-to human transmission, it can cause an influenza pandemic. The impact of a pandemic caused by such a virus is difficult to predict: it depends on virulence of the virus, existing immunity among people, cross protection by antibodies acquired from seasonal influenza infection and host factors.
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Diagnosis
To diagnose swine influenza A infection, a respiratory specimen would generally need to be collected within the first 4 to 5 days of illness (when an infected person is most likely to be shedding virus). However, some persons, especially children, may shed virus for 10 days or longer. Identification as a swine flu influenza A virus requires sending the specimen to CDC for laboratory testing.
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Treatment
There are four different antiviral drugs that are licensed for use in the US for the treatment of influenza: amantadine, rimantadine, oseltamivir and zanamivir.
While most swine influenza viruses have been susceptible to all four drugs, the most recent swine influenza viruses isolated from humans are resistant to amantadine and rimantadine. At this time, CDC recommends the use of oseltamivir or zanamivir for the treatment and/or prevention of infection with swine influenza viruses.
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Illustrations
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The Hsw1N1 virus seen through a colorized transmission electron micrograph.
The Hsw1N1 virus causes Swine Influenza (swine flu) which is a respiratory disease of pigs caused by type A influenza that regularly results in outbreaks of influenza among pigs. Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred including the current outbreaks in Mexico and USA.
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News
A/H1N1 influenza like human illness in Mexico and the USA: OIE statement
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