Information Regarding Swine Flu

With the goal of reducing transmission and illness severity, the Centers for Disease Control and Prevention and the Southwest Center for Public Health Preparedness is providing information to help the general public, health care providers, & public health officials address challenges posed by the swine influenza virus.

CDC states that this is an evolving situation and updated guidance and new information will be posted as it becomes available. Please visit their websites to receive these recent updates at http://www.cdc.gov/swineflu/index.htm . 

For concerned parents and caregivers, visit their website at http://www.cdc.gov/swineflu/parents.htm .

For answers to your questions about pandemics and flu, please read the information below or view a printable fact sheet at http://www.toucaned.com/SwineFluFactSheet.pdf . And for proper hand washing techniques, you may view this video from the CDC  http://www.cdc.gov/CDCTV/HandsTogether/        

 

Swine Flu Fact Sheet

What is ‘swine flu’?
Swine flu is a strain of influenza that is found in swine. Influenza is a group of RNA viruses that can infect many types of animals. According to the strict definition of swine influenza, it would be a strain of influenza that infects swine only, and would not be spread easily to humans or any other animal.

The current strain of ‘swine flu’ is a strain of influenza that originates from swine, but also has genes (RNA) from other animal-specific strains of influenza, including human (seasonal) influenza strains and avian strains. Hence, the current strain of ‘swine flu’ is a mutated influenza virus that is human, swine, and avian all at the same time.

How does ‘swine flu’ compare to ‘seasonal flu,’ ‘bird flu,’ and ‘stomach flu’?
As mentioned above, influenza is a group of viruses that can infect many types of animals. Some strains are specific to humans (referred to as seasonal influenza), while some strains are specific to swine (‘swine flu’), birds (‘bird flu’), horses, etc.

The concern arises when animal-specific strains of influenza mix and form strains that cross the animal species barrier. The following two events need to occur:

1. The new influenza strain with animal origins needs to infect humans with relative ease.
2. The new influenza strain with animal origins needs to be transmitted person-to-person with relative ease.

The current strain of ‘swine flu’ has done both of these things. There is sustained person-to-person transmission resulting in a strain of influenza that although had origins in swine, is now adapted to a human host.

‘Stomach flu’ is a misnomer. When people have severe diarrhea, nausea, and vomiting as the primary symptoms, the disease is not cause by an influenza virus. It should be noted that the current strain of ‘swine flu’ causes some symptoms of diarrhea, nausea, and vomiting in some proportion of those infected. However, the primary symptoms are still cough, fever (above 100.4°F), sore throat, and myalgias (aches and pains).

What is the difference between an epidemic and a pandemic?
Epidemic - disease is at an abnormally high level among the effected population(s).
Pandemic - disease is at an abnormally high level for populations around the world.  The disease has spread around the globe. 

In terms of influenza, pandemic influenza is likely to arise when a new strain of influenza emerges. New strains are expected to have origins from swine and/or birds.

Why does influenza change all the time?
Influenza is an RNA virus. This means it is much more prone to mutations than if the genetic material was DNA. In addition, the RNA genome has 8 different segments. This segmented genome facilitates re-assortment where segments from one strain can combine with the genome of an entirely different strain.

There are two important genetic changes the influenza virus may undergo: antigenic drift and antigenic shift.

Antigenic drift is a minor change in the genetic make up of the virus that occurs due to ordinary changes in the genome of the virus during replication.  This process of antigenic drift allows the influenza virus to change and re-infect people repeatedly from season to season, which is why people must get a new vaccine with the updated influenza strain every year. 

Antigenic shift is much rarer and is where reassortment of the genome occurs. The result is people have no immunity to this new strain of virus.  Because this is a sudden change, there is no vaccine available. Therefore the entire human population is capable of being infected with this new virus, which is a key condition for the occurrence of a pandemic infection.

Why doesn’t the current influenza vaccine protect against ‘swine flu’?
The annual influenza vaccine is developed to protect against the mostly likely strains of influenza currently circulating in the world. Although vaccine developers try to account for small seasonal change (antigenic drift), it is nearly impossible to account for major changes in the influenza virus (antigenic shift). Hence, now that the new strain of ‘swine flu’ has emerged, vaccine developers are trying to make a vaccine that matches the newly identified strain.

What are the symptoms of ‘swine flu’?
The symptoms of ‘swine flu’ are similar to normal (seasonal) influenza. Cough, fever (above 100.4 °F), sore throat, and myalgias (aches and pains) are the primary symptoms. Some diarrhea, nausea, and vomiting have also been reported to occur with this new strain of ‘swine flu.’

How does a person get tested for or diagnosed with ‘swine flu’?
A respiratory swab is taken by a clinician and sent to the state public health laboratory. Either real-time RT-PCR (reverse transcriptase-polymerase chain reaction) or viral culture is confirmatory. Results from RT-PCR are quicker than viral culture. The sensitivity of the rapid influenza test for diagnosing ‘swine flu’ is currently unknown. A positive test in a person with influenza-like symptoms should be interpreted as a true positive. However, a negative test from a rapid influenza test may be a false negative.

What is the case fatality rate for ‘swine flu’?
Nobody knows what the true case fatality rate is for the current strain of swine flu. To answer this question, you need to know:

1. how many people infected with ‘swine flu’ died, and
2. the total number of people infected with  swine flu

Because it is possible that many people have been infected with ‘swine flu’ and never saw a doctor, or did see a doctor but never got tested for ‘swine flu’, it is likely that the true number of people infected with ‘swine flu’ is much higher than the number reported in the news.

As of April 29, there are 148 confirmed humancases of swine flu. There have been 8 deaths among confirmed cases. Based on this information, the case fatality rate = 8/148 = 5.4%. In the U.S. the case fatality rate among confirmed cases is 1/91 = 1.1%.

Pandemic flu is capable of infecting a large number of people because there is little or no pre-existing immunity.  Healthy people may be at increased risk of serious complications, whereas with the seasonal flu the people at increased risk for complications are the very young, elderly, and those with underlying health conditions. 

If a person is infected with ‘swine flu’, how long are they infectious to other people?
Data specific to swine flu are unavailable, thus, data from seasonal influenza are used as guidance. Infected adults can typically transmit influenza from the day before they start having symptoms until symptoms resolve or up to 7 days after the onset of their symptoms. Children may be infectious longer than adults (e.g., 10 days).

The incubation period (or the time between infection and symptom onset) can be anywhere from 1-4 days with a mean incubation time of 2 days. Thus, if a person is believed to be exposed to ‘swine flu’, it may be necessary to wait for a maximum of 4 days to determine if an exposed person got infected.

How is ‘swine flu’ treated?
CDC recommends the use of oseltamivir (Tamiflu) or zanamivir (Relenza) for the treatment and/or prevention of infection with these swine influenza viruses. Antiviral drugs are prescription medicines (pills, liquid or an inhaler) that fight against the flu by keeping flu viruses from reproducing in the body. If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious flu complications. For treatment, antiviral drugs work best if started soon after getting sick (within 2 days of symptom onset).

How does ‘swine flu’ spread?
‘Swine flu’ is believed to be spread the same way seasonal influenza is spread. That is, primarily by respiratory secretions generated by coughing and sneezing. A secondary mode of transmission is through contaminated objects, like hands picking up the virus from a contaminated object and then delivering the virus to one’s own mouth, nose, or eyes.

How can I prevent the transmission of ‘swine flu’?
Hand and respiratory hygiene are extremely important in reducing the transmission of infection.  Regularly wash hands with alcohol-based gels or soap and water. Cough into tissues and promptly throw tissues away. If no tissue is available, cough into your sleeve/elbow instead of your hands.

Can I get swine influenza from eating or preparing pork?
No. Swine influenza viruses are not spread by food. You cannot get swine influenza from eating pork or pork products. Eating properly handled and cooked pork products is safe.

For additional information, please visit the CDC’s website Swine Influenza and You at
http://www.cdc.gov/swineflu/swineflu_you.htm