(See also Influenza Influenza (Flu) Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more .)
In 2009, there was an epidemic of a new strain of influenza virus that became so widespread that it was considered a pandemic (a major worldwide epidemic). This strain was an H1N1 influenza virus (see types and strains of influenza Influenza types and strains Influenza (flu) is a viral infection of the lungs and airways with one of the influenza viruses. It causes a fever, runny nose, sore throat, cough, headache, muscle aches (myalgias), and a general... read more ) that had a combination of genes from pig (swine), bird, and human influenza viruses. Because the first reports focused on the swine component, it was referred to publicly as "swine flu," although it was not acquired directly from pigs. People acquired this influenza virus infection from other infected people (person to person spread) like ordinary flu.
Unlike ordinary flu, pH1N1 flu is more likely to occur in and to cause death in young and middle-aged adults than in older people. This is because the pH1N1 strain was so different from any recent strains of flu.
Pigs can be infected by certain strains of influenza virus, which are more correctly termed "swine flu." Most strains of swine influenza virus are slightly different from those that infect people. These strains very rarely spread to people, and when they do, they very rarely then spread from person to person. However, one variant strain of swine flu virus, H3N2v, has infected children and adults in several U.S. states. Infected people had contact with apparently healthy but infected domestic pigs, usually at agricultural fairs. Also, in a few cases, the virus may have spread from person to person.
Symptoms of H1N1 influenza are typically flu-like. They include fever, cough, sore throat, body aches, headache, chills, runny nose, and fatigue. Nausea, vomiting, and diarrhea are also common.
In most people, symptoms seem to develop from 1 to 4 days after exposure to the virus and continue for up to another week. People can spread the infection for about 8 days, from the day before symptoms appear until symptoms are gone.
Symptoms are usually mild but can become severe, leading to pneumonia Overview of Pneumonia Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them. Pneumonia is one of the most common causes of death worldwide. Often, pneumonia is the final... read more or respiratory failure Respiratory Failure Respiratory failure is a condition in which the level of oxygen in the blood becomes dangerously low or the level of carbon dioxide in the blood becomes dangerously high. Conditions that block... read more . The infection can make chronic disorders (such as heart and lung disorders and diabetes Diabetes Mellitus (DM) Diabetes mellitus is a disorder in which the body does not produce enough or respond normally to insulin, causing blood sugar (glucose) levels to be abnormally high. Urination and thirst are... read more ) worse and, during pregnancy, can cause complications (such as miscarriage Miscarriage A miscarriage is the loss of a fetus due to natural causes before 20 weeks of pregnancy. Miscarriages may occur because of a problem in the fetus (such as a genetic disorder or birth defect)... read more or premature birth Premature Newborn A premature newborn is a baby delivered before 37 weeks of gestation. Depending on when they are born, premature newborns have underdeveloped organs, which may not be ready to function outside... read more ).
At high risk of complications are children under 5 years old and people with kidney or liver disorders or a weakened immune system Overview of the Immune System The immune system is designed to defend the body against foreign or dangerous invaders. Such invaders include Microorganisms (commonly called germs, such as bacteria, viruses, and fungi) Parasites... read more due to drugs or disorders such as AIDS Acquired immunodeficiency syndrome (AIDS) Human immunodeficiency virus (HIV) infection is a viral infection that progressively destroys certain white blood cells and can cause acquired immunodeficiency syndrome (AIDS). HIV is transmitted... read more . Severe complications can develop and progress rapidly—sometimes, even in young, healthy people.
If symptoms are mild or typical, particularly when pH1N1 influenza is widespread, testing is usually not required. pH1N1 influenza can be usually be diagnosed based on symptoms and results of a physical examination.
Doctors may take samples of secretions from the nose and mouth for testing. This testing can confirm H1N1 infection.
People with flu-like symptoms should stay home, cover their mouth and nose with a tissue when sneezing or coughing, wash their hands frequently, and use an alcohol-based hand sanitizer.
People who have been in close contact with someone who has pH1N1 flu may be given antiviral drugs Antiviral drugs A virus is composed of nucleic acid, either DNA or RNA, surrounded by a protein coat. It requires a living cell in which to multiply. A viral infection can lead to a spectrum of symptoms from... read more .
People should see a doctor immediately if they have severe vomiting, shortness of breath, chest or abdominal pain, or sudden dizziness or confusion.
Children should be taken to a doctor immediately if they have blue lips or skin, are not drinking enough fluids, are breathing rapidly or with difficulty, are unusually drowsy or irritable (including not wanting to be held), or have a fever with a rash.
If people at high risk of severe complications (including children under 5 years old) or pregnant women have even mild symptoms, a doctor should be contacted.
Also, if a fever and a worse cough develop after flu-like symptoms disappear in any person, a doctor's attention is required.
Treatment of pH1N1 influenza focuses on relieving symptoms. For example, acetaminophen can relieve fever and aches. Getting enough rest and drinking plenty of fluids can help.
The antiviral drugs Antiviral drugs A virus is composed of nucleic acid, either DNA or RNA, surrounded by a protein coat. It requires a living cell in which to multiply. A viral infection can lead to a spectrum of symptoms from... read more oseltamivir, zanamivir, or baloxavir may be used if people are at risk of complications or have severe symptoms. These drugs are most effective when started within 48 hours after symptoms appear. In the United States, most people have recovered from pH1N1 influenza fully without taking these drugs.