What is swine flu?

Swine flu is a highly contagious acute respiratory disease found in pigs. It is caused by one of the swine influenza A viruses. Swine flu results in high morbidity and low mortality of about 1-4%. Amongst the pigs themselves, the virus spreads through aerosols, direct and indirect contact, and through asymptomatic carrier pigs. Although the pigs are prone to regular infections, incidences increase in the fall and winter months in the temperate zones. Therefore, pigs are routinely vaccinated against swine influenza in many countries.

Swine influenza viruses though commonly belong to the H1N1 subtype, other subtypes like H1N2, H3N1, H3N2 are also known to be circulating in pigs. Pigs, on the other hand, are more susceptible to being infected with avian influenza viruses, human seasonal influenza viruses and swine influenza viruses, allowing the genes from the viruses to mix and result in an influenza virus containing genes from a number of sources; this is called a “reassortant” virus. Although swine influenza viruses are species specific, they can in extreme conditions make a crossover to cause disease in humans.

How is swine flu diagnosed?

When a person is under the weather, many symptoms may be present. However, symptoms of swine flu are very similar to normal cold and flu symptoms, and may include:

Headache Fever Cough Appetite loss Fatigue Sore throat Runny nose Chills Nausea Vomiting Diarrhea

Fatigue, appetite loss and diarrhea can be dangerous. If the symptoms are persistent, it becomes imperative that you see a doctor. In order to diagnose your illness, the doctor may order:

Chest x-rays Respiratory specimen Blood work

To diagnose swine influenza A infection, a respiratory specimen must be collected within the first 4 to 5 days of the onset of the illness as this is the time when the infected person is most likely to be shedding virus; however, children especially, may be shedding the virus for 7 days or longer. In order to identify the swine influenza A virus, the specimen must be sent to the CDC for laboratory testing. Only RT-PCR or viral culture has the potential to confirm infection with swine-origin influenza A (H1N1) virus. The test performance of rapid antigen tests and immunofluorescence tests for detection of swine-origin influenza A (H1N1) virus is unknown. Persons who are suspected of having swine-origin influenza A (H1N1) virus and who test positive for the same using one of these tests should then have confirmatory RT-PCR or viral culture testing to confirm the presence of swine-origin influenza A (H1N1) virus. A negative rapid antigen or immunofluorescence test cannot be used to rule out swine-origin influenza A (H1N1) virus infection. The results of this test from nasopharyngeal or nasal swab, along with other information, will in all probability help your doctor take better care of you. Knowing the test results will help prevent the spread of the virus to others.

The Swine Influenza Test Kit is a sensitive test to detect the swine flu virus; however, the FDA has not cleared or approved this test. But it has been agreed by the FDA has agreed that this test can be used under an Emergency Use Authorization.

How is swine flu different from bird flu?

The swine flu and the bird flu viruses do not have a twin-like similarity but are however quite similar. The virus that causes bird flu in humans first mutated from a virus that birds had so that it could then be passed on to humans; once established, it now passes from human to human contact. Same is the case with swine flu. It started among pigs as a virus but then soon mutated to spread to humans. Viruses have the ability to replicate rapidly; these viruses are able to mutate very quickly thereby creating new strains that then move on to multiply in other areas and susceptible hosts. Avian flu so far has found it difficult to infect humans unless they were exposed to birds intensely. This is because the virus has not mutated in a way that makes it transmissible by one human to another. However, the swine flu virus has genetic origins from both pigs and birds. The biggest difference here is that the swine flu virus has mutated to an extent where it can readily be transmitted on human to human contact.

What drugs are available to treat swine flu and bird flu?

Antiviral treatment is normally the first line of treatment for the confirmed, probable or suspected cases of swine-origin influenza A (H1N1) virus infection, prioritizing treatment of hospitalized patients and patients with high risk for complications. Antiviral drugs are prescription medicines (pills, liquid or an inhaler) with actively works against influenza viruses, including the swine influenza virus. Antiviral drugs are generally used to treat swine flu or to prevent infection with swine flu viruses. These medications are prescribed by a health care professional.

As of today, four influenza antiviral drugs are approved for use in the United States. They are:

Oseltamivir (Tamiflu) Zanamivir (Relenza) Amantadine Rimantadine (Flumadine)

Laboratory testing conducted on the swine influenza A (H1N1) viruses so far has indicated that the viruses are susceptible (sensitive) to oseltamivir and zanamivir. Antiviral drugs can make the illness milder as well prevent serious influenza complications. However, these antiviral drugs work best when they are started within two days of the onset of the illness. Antiviral drugs can also be used as a preventive measure to protect a person who has been or may be near a person with swine flu. Antiviral drugs are about 70% to 90% effective in preventing the flu.

Antiviral doses recommended for treatment of swine-origin influenza A (H1N1) virus infection in adults or children 1 year of age or older are the same as those recommended for seasonal influenza. Oseltamivir use in children less than 1 year of age was recently approved by the U.S. FDA under an Emergency Use Authorization (EUA).

Moreover, there are vaccines available that can be given to pigs to prevent swine influenza from spreading. Nonetheless, there is no vaccine to protect humans from swine flu yet. It is believed that the seasonal influenza vaccine will likely help provide partial protection against swine H3N2, but not swine H1N1 viruses.