In April of 2009, the H1N1 or swine flu, a new influenza virus, was detected in people in the United States. This virus is referred to as “swine flu” because lab testing showed that many of its genes are similar to influenza viruses that are in pigs (swine) in North America. However, further study shows the new virus has two genes from flu viruses in pigs in Europe and Asia, bird (avian) genes, and human genes. On June 11, 2009, the World Health Organization (WHO) declared H1N1 flu a global pandemic when the infection had been verified worldwide.

There are 3 types of influenza viruses A, B, or C based on their protein composition. Type A viruses are found in ducks, chickens, pigs, whales, and humans. Type B virus circulates in humans. Type C is found in humans, pigs, and dogs. Type A influenza responsible for the global outbreaks of 1918, 1957, and 1968. Type A viruses are further divided into groups based on two surface proteins, HA and NA. There are 16 HA subtypes and 9 NA subtypes.

Subtypes A are classified by a naming system of place the strain was found, year it was discovered, lab identification number, and its type (HA and NA). If the virus infects non-humans, the host species is included before the geographical site. For example A/Chicken/Hong Kong/G9/97 (H9N2). There are no type B or C subtypes. 

The flu virus exists in wild aquatic birds such as ducks and shore birds for millions of years. However, mutating flu viruses can transfer from wild birds (avian) to domesticated ducks, to chickens, and then pigs (swine). Pigs can be infected by both influenzas from birds and from humans. In a farm where chickens, humans, and pigs live in close proximity, pigs are influenza virus “middle men”. If a pig is infected with avian and human flu simultaneously, the two types of virus may exchange genes and spread from pigs to people.

A flu virus is almost round, elongated, or irregular shape. It has eight segments of single-strand RNA containing the genetic instructions for making new copies of the virus with a layer of spikes projecting from its surface. There are two different types of spikes, the protein hemagglutinin (HA) helps the virus to attach to a cell and initiate infection, and protein neuraminidase (NA) make possible for newly formed viruses to coexist in the host cell.

The symptoms of H1N1 flu virus are similar to the infection of other flu: fever, cough, sore throat, body aches, headache, chills, fatigue, diarrhea, and vomiting. Swine flu symptoms develop three to five days after exposure and continue for about eight days later. Severe complications of human swine flu H1N1 seem to develop and progress rapidly. Influenza complications include worsening of chronic conditions, such as heart disease, diabetes and asthma, pneumonia and respiratory failure.

Influenza viruses infect the cells lining the nose, throat, and lungs. The virus enters humans when they inhale contaminated droplets or transfer live virus from contaminated surfaces to the eyes, nose or mouth on their hands. People infected with seasonal and H1N1 flu shed virus and may be able to infect others from one day before getting sick to five to seven days after. This can be longer in children and people with weakened immune systems and in people infected with the new H1N1 virus.

• Swine flu can be spread about 24 hours before symptoms develop and ending seven days later. Stay out of the emergency room, doctor's office or urgent-care center because medical facilities are where others receiving care and are vulnerable to the flu.
• Always cover when coughing and sneezing. Wash hands thoroughly (sing Happy Birthday twice is how long it takes) and frequently with soap and water or use an alcohol-based hand sanitizer because flu viruses can survive for two hours or longer on surfaces, such as doorknobs and countertops.
• Avoid contact and stay away from crowds. If a member of your household has swine flu, designate one household member to care for the sick person.

Influenza vaccines are one of the most effective ways to protect people from contracting illness during influenza epidemics and pandemics. These vaccines will boost immunity against the new influenza, and help ensure public health as the pandemic evolves. The antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) can reduce the severity of symptoms, but flu viruses can develop resistance to them. To prevent development of drug resistance and maintain supplies of these drugs, antiviral are reserved for people at high risk of complications. In the United States, vaccination is recommended for

• Pregnant women because mothers can provide protection to infants who cannot be vaccinated.
• Household contacts and caregivers for children younger than 6 months of age to reduce the infants' risk of exposure to the virus because infants are at higher risk of flu complications and cannot be vaccinated
• Health care and emergency medical services personnel because infections were reported among health care workers and are potential source of infection for vulnerable patients, reduce absenteeism in health care workers, and increase health care system capacity.
• Babies, children, and teens, from 6 months through 18 years of age because there are many H1N1 influenza cases have occurred in children. Influenza viruses spread easily in school and childcare, and children infected in these settings spread the virus to their families.
• Young adults, from 19 through 24 years of age because they live, work, and study in close proximity. They also move and travel often.
• People ages 25 through 64 years who have heart disease, lung disease and some types of cancer are at higher risk of medical complications from influenza.

People who are sick with any type of flu should:

• Drink plenty of water, juice, and clear broth to prevent dehydration. Drink enough to have clear or pale yellow urine.
• Get more sleep to help the immune system fight the infection.
• Take over-the-counter medication like acetaminophen Tylenol, Ibuprofen, Advil, Motrin to reduce fever and aches. However, children and teens should not take aspirin because of the risk of Reye's syndrome, which is rare but potentially fatal disease.

In seasonal flu, people are 65 years and older, children younger than five years old, pregnant women, diabetes, heart disease, asthma and kidney disease are at “high risk” of serious complications. About 70% of people who have been hospitalized with this H1N1 virus have had one or more medical conditions previously recognized. While most people who have been sick have recovered without needing medical treatment, hospitalizations and deaths from infection with this virus have occurred.

CDC laboratory studies show that about one-third of adults older than 60 may have antibodies against this virus. No children and very few adults younger than 60 years old have existing antibody to H1N1 flu virus and are at high risk of serious complications from H1N1. While people 65 and older are the least likely to be infected with H1N1 flu, they are also at “high risk” of developing serious complications from their illness if they get sick.

At the Weekly 2009 H1N1 Flu Media Briefing on November 6, 2009, Doctor AnneSchuchat said that the flu is still widespread with 48 states. The rates of disease are higher than normal for this time of year. More than half the hospitalizations are in people under 25 and 90% of the deaths are in people under 65. Most of the illness is in younger people. The pediatric deaths are high and children have died from flu where the typing was not done, but that is an increase from last week's number. Two-thirds of the children who died from the H1N1 virus have underlying condition like severe neurological problems, cerebral palsy and muscular dystrophy and asthma, which increase their risk of this problem and contributing to the severe outcomes.

Fortunately, antiviral are effective treatment against flu, including the flu complications. There twice as much vaccine available as two weeks ago, 38 million doses of H1N1 vaccine available for ordering by the states.  Most of them are inject doses, one third are spray form recommended for people who are healthy between the ages of 2 and 49 years of age. The number is up more than 11 million doses from October 31. There will be about 8 million doses to be available in the week.

Here are more articles about flu and viruses.