Understanding Swine Flu

Understanding Swine Flu Outbreak: Questions and Answers

By John Lauerman

April 27 (Bloomberg) -- Swine flu, a virus that normally infects pigs, has been detected in people in Mexico, the U.S., New Zealand, Canada, and the U.K. Health officials around the world are checking to see whether infections have occurred in their countries, and readying measures to prevent its spread.

Here are answers to some frequently asked questions about swine flu. The information is drawn from the data released by the World Health Organization in Geneva and the U.S. Centers for Disease Control and Prevention in Atlanta.

Q: What is swine flu? A: Influenza is a virus that infects people, birds, pigs and other animals such as ferrets. Swine flu, or swine influenza, is a form of the virus that normally infects pigs. There are many forms of flu, and the different varieties have the ability to exchange genes with one another. The form of flu that originated in Mexico is a genetic mixture of viruses that have been seen in pigs, birds and people. It’s being called a swine flu because the overall structure of the virus is of the type that affects pigs, said Keiji Fukuda, a WHO official.

Q: How do people catch swine flu? A: Studies are still ongoing on how this particular swine flu is transmitted. Flu is generally transmitted through the respiratory tract. Droplets of infected body fluids can carry flu when people cough or sneeze. Studies indicate that masks called N95 respirators that, when properly used, filter germs from the breath and hamper the spread of flu. Neither contact with pigs nor eating pork has been linked to the spread of the flu, Fukuda said today. Still, health researchers are working to establish that the virus is spreading from person-to-person.

Q: What are the symptoms of swine flu? A: About one to four days usually elapse between the time a person is infected and the onset of symptoms. Influenza normally causes symptoms such as coughing, sneezing, headaches and body aches, fever, chills, and sometimes vomiting and diarrhea. Swine flu causes the same symptoms, and may be difficult to distinguish from other strains of flu and respiratory illnesses. Severe cases of flu that lead to death are normally seen in very young and very old people whose immune systems are too weak to fight off the virus. Adults with severe illness may also have difficulty breathing, dizziness, confusion, or severe vomiting and diarrhea.

Q: How can I tell if my child is sick? A: Children who are breathing abnormally fast or slowly may have respiratory illness. Bluish skin indicates a need for quick attention. Children who are abnormally sluggish and sleepy, irritable, or have fever or rash may also need attention.

Q: Have there been outbreaks of swine flu before? A: Yes. Health officials said in 1976 that an outbreak of swine flu in people might lead to a pandemic. Widespread vaccination was carried out in the U.S. before experts determined that the virus was not dangerous enough to cause a pandemic. Swine flu occasionally infects people in the U.S. without causing large outbreaks. From 2005 through January 2009, there were 12 reported swine flu cases in the U.S. None of them caused deaths.

Q: Why are health officials concerned about the outbreak of swine flu? A: When flu viruses mix their genes with one another, they can take on new forms. New flu viruses are harder for the immune system to defend against. With little or no opposition from the immune system, they can grow quickly and invade many tissues and organs. They may also set off a harmful immune overreaction in the body, called a “cytokine storm,” that may be lethal in itself. The swine flu virus from Mexico may have the ability to spread quickly and kill people, possibly causing a worldwide pandemic, according to the World Health Organization. Researchers are conducting studies right now to determine how easily the virus spreads in people and how dangerous it is.

Q: What’s a flu pandemic? A: Flu pandemics occur when new influenza viruses emerge that spread quickly and few people have immunity to them. While influenza viruses were only discovered about a century ago, researchers believe flu pandemics hit about twice or three times each century. Some pandemics are relatively mild, killing just a few million people globally. The most severe flu pandemic on record was the 1918 Spanish Flu, and researchers estimate it killed about 50 million people around the world.

Q: Are there any similarities between the swine flu and earlier pandemic viruses? A: Flu viruses are classified by two proteins on their surface, called H for hemagglutinin and N for neuraminidase. Both the swine flu found in Mexico and the 1918 Spanish Flu viruses are of the H1N1 subtype. Both viruses appear to have originated in animals; researchers believe the Spanish flu spread to people from birds. The two viruses are not identical, and there are still many genetic differences between them that researchers are studying.

Q: Do all H1N1 viruses cause pandemics? A: Not all H1N1 viruses cause pandemics. H1N1 descendants of the Spanish Flu virus continue to circulate in people and sometimes cause outbreaks of seasonal flu.

Q: Is there a vaccine against the swine flu from Mexico? A: Flu vaccines generally contain a dead or weakened form of a circulating virus. The vaccine prepares the body’s immune system to fend off a true infection. For the vaccine to work, it must match the circulating, “wild-type” virus relatively closely. There is no vaccine currently that exactly matches the swine flu. However, if the virus is sufficiently similar to circulating forms of H1N1 flu that are included in current vaccines, they may offer some limited protection from swine flu. While U.S. health officials are investigating this, the possibilities for this protection are poor, they said yesterday on a telephone call.

In addition, millions of people in the U.S. were vaccinated against swine flu in 1976. While that was not the same strain of flu as the one from Mexico, people who got the 1976 vaccine may get some limited protection from the currently circulating virus. Health officials may do some research on this issue as well.

Vaccine makers have contacted the World Health Organization about obtaining samples of the virus needed to make a vaccine. Making flu vaccine can take three to six months, depending on the type of manufacturing used.

Q: Are there drugs that treat swine flu? A: Roche Holding AG’s Tamiflu and GlaxoSmithKline Plc’s Relenza both have activity against swine flu. The U.S. has released its stockpile of Tamiflu to treat people with swine flu. Flu viruses sometimes develop resistance to antiviral drugs. The human form of H1N1 that’s currently circulating is resistant to Roche’s Tamiflu (not Relenza). If the two viruses were to exchange genes, the swine flu might become resistant, too.

Q: How else can I protect myself from swine flu? A: Personal hygiene measures, such as avoiding people who are coughing or sneezing and frequent hand-washing, may prevent flu infection. Those who aren’t health professionals should avoid contact with sick people, or those who are coughing or sneezing. People who get sick with flu symptoms should stay home. Studies have suggested that closing schools, theaters, and canceling gatherings in the early stages of a pandemic can limit its spread. Such measures would likely take place if health officials determine that the virus is spreading quickly enough and is deadly enough to cause a pandemic.

To contact the reporter on this story: John Lauerman in Boston at jlauerman@bloomberg.net; Jason Gale in Singapore at j.gale@bloomberg.net

Last Updated: April 26, 2009 22:29 EDT