What is swine flu?

The H1N1 flu, often called "swine flu," isn't related to pigs. It's a new flu virus circulating among people. First seen in April 2009, the H1N1 flu virus has gone on to become a "pandemic," which means that it has been seen worldwide.

The 2009 flu pandemic is a global outbreak of a new strain of influenza A virus subtype H1N1, termed Pandemic H1N1/09 virus by the World Health Organization (WHO), that was first identified in April 2009. The disease has also been termed 2009 H1N1 Flu by the U.S. Centers for Disease Control and Prevention (CDC), and colloquially called swine flu.

The outbreak was first observed in Mexico, with evidence that there had been an ongoing epidemic for months before it was officially recognized as such.The Mexican government soon closed most of Mexico City's public and private offices and facilities to contain the spread of the virus. As the virus quickly spread globally, clinics were overwhelmed by testing and treating patients, and the WHO and the CDC eventually stopped counting all cases and focused instead on tracking major outbreaks. On June 11, 2009, WHO declared the outbreak to be a pandemic.
Only mild symptoms are experienced by the overwhelming majority of victims, but there are exceptions. Some persons are in higher risk groups, such as those with asthma, diabetes, obesity, heart disease, children with neurodevelopmental conditions, or persons who are pregnant or have a weakened immune system. And there are small subsets of patients, even among young persons previously healthy, in which the patient rapidly develops severe pneumonia, typically 3 to 5 days after initial onset of symptoms. Deterioration can be very rapid, with many patients progressing to respiratory failure within 24 hours, requiring intensive care and ventilation support. And there is a somewhat different pattern in which a child, including a child who is generally quite healthy, seems to be recovering and then relapses with high fever. This can be a secondary infection of bacterial pneumonia, which needs treatment with antibiotics.

Like other influenza viruses, novel H1N1 influenza is typically contracted by inhaling air that has been contaminated by an infected person coughing or sneezing, or by touching one's nose or mouth with hands that have previously touched contaminated surfaces and have not been disinfected.
Symptoms, which last up to a week, are similar to those of seasonal flu, and can include fever, sneezing, sore throat, cough, headache, and muscle or joint pains. To avoid spreading the infection, the CDC recommended that those with symptoms stay home from school, work, and crowded settings; in general, wearing facial masks was not recommended, except in health care settings.

Symptoms and severity

The symptoms of swine flu are similar to other influenzas, and may include a fever, coughing (typically a "dry cough"), headaches, pain in the muscles or joints, sore throat, chills, fatigue, and runny nose. Diarrhea, vomiting, and neurological problems were also reported in some cases. People at higher risk of serious complications include people age 65 and older, children younger than 5 years old, children with neurodevelopmental conditions, pregnant women, and people of any age with underlying medical conditions, such as asthma, diabetes, obesity, heart disease, or a weakened immune system (e.g., taking immunosuppressive medications or infected with HIV). Most hospitalizations in the US were people with such underlying conditions, according to the CDC.

A New England Journal of Medicine article on hospitalized United States H1N1 patients from April to mid-June found that 40% of them had chest X-rays consistent with pneumonia. And if the same pattern holds from the 1957-58 pandemic, then approximately two-thirds of these patients had viral pneumonia and one-third had bacterial pneumonia. However, antiviral medication was received by only 73% of the patients, whereas 97% received antibiotics. It is recommended that such patients receive both.

A study from Australia and New Zealand estimated that the demand for ICU beds due to viral pneumonia was much higher during the pandemic than in previous influenza seasons. A Canadian study reported that intensive care capacity in Winnipeg, Manitoba was "seriously challenged" at the peak of the outbreak, with full occupancy of all regional ICU beds. The average age of ICU patients was 32, 40, and 44 years in Canada, Australia/New Zealand, and Mexico respectively.

In adults

In adults, shortness of breath, pain in the chest or abdomen, sudden dizziness, or confusion may require emergency care. In both children and adults, persistent vomiting or the return of flu-like symptoms that include a fever and cough may require medical attention. And if it follows the same pattern as in children, a relapse with high fever may in fact be pneumonia.
Dr. Thomas R. Frieden, Director of the CDC, suggests that people with "underlying conditions" who come down with flu symptoms should consult their doctors first before visiting an "emergency room full of sick people," since it "may actually put them in more danger." This was especially true of pregnant women.

In children

Influenza-associated pediatric deaths reported to CDC, from 2005–06 to start of 2009–2010.
As with the seasonal flu, certain symptoms may require emergency medical attention. In children, signs of respiratory distress include blue lips and skin, dehydration, rapid breathing, excessive sleeping, seizures and significant irritability including a lack of desire to be held. Although "too early" to tell for certain, Dr. Frieden has noted that so far the swine flu "seems to be taking a heavier toll among chronically ill children than the seasonal flu usually does." Of the children who have died so far, nearly two-thirds had pre-existing nervous system disorders, such as cerebral palsy, muscular dystrophy, or developmental delays. "Children with nerve and muscle problems may be at especially high risk for complications," the CDC report stated. In children without chronic health problems, it is a warning sign if they seem to recover from the flu but then relapse with a high fever, Dr. Frieden added. The relapse may be bacterial pneumonia, which must be treated with antibiotics.
Researchers in Australia and New Zealand have reaffirmed that infants under the age of 1 year have the highest risk of developing severe illness from swine flu.

The United States authority on disease prevention, the Centers for Disease Control and Prevention (CDC), recommends that persons suffering from influenza infections:

• Stay at home
• Get plenty of rest
• Drink a lot of liquids
• Do not smoke or drink alcohol
• Consider over-the-counter medications to relieve flu symptoms
• Consult a physician early on for best possible treatment
• Remain alert for emergency warning signs.

Warning signs are symptoms that indicate that the disease is becoming serious and needs immediate medical attention. These include:

• Difficulty breathing or shortness of breath
• Pain or pressure in the chest or abdomen
• Dizziness
• Confusion
• Severe or persistent vomiting

In children other warning signs include irritability, failing to wake up and interact, rapid breathing, and a blueish skin color. Another warning sign in children is if the flu symptoms appear to resolve, but then reappear with fever and a bad cough

The Mayo Clinic and Medline listed ways to help ease symptoms, including adequate liquid intake and rest, soup to ease congestion, and over-the-counter drugs to relieve pain. Aspirin was a very effective way to treat fever in adults, although in children and adolescents, aspirin is contraindicated due to the risk of Reye's syndrome. While over-the-counter drugs relieve symptoms, they do not kill the virus. Most patients were expected to recover without medical attention, although those with pre-existing or underlying medical conditions were more prone to complications.

The initial outbreak received a week of near-constant media attention. Epidemiologists cautioned that the number of cases reported in the early days of an outbreak can be very inaccurate and deceptive due to several causes, among them selection bias, media bias, and incorrect reporting by governments. Inaccuracies could also be caused by authorities in different countries looking at differing population groups. Furthermore, countries with poor health care systems and older laboratory facilities may take longer to identify or report cases. Dr. Joseph S. Bresee (the CDC flu division's epidemiology chief) and Dr. Michael T. Osterholm (director of the Center for Infectious Disease Research) have pointed out that millions of people have had swine flu, usually in a mild form, so the numbers of laboratory-confirmed cases were actually meaningless, and in July 2009 the WHO stopped keeping count of individual cases and focused more on major outbreaks.