Is Swine Flu (H1N1) Contagious?

  • Medical Author:
    Charles Patrick Davis, MD, PhD

    Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What is swine flu?

Swine flu is a term that is being replaced by the designation H1N1 influenza and refers to a particular type of influenza virus that has a genetic makeup that includes viral genes that are associated with the infection of pigs. Swine flu was the cause of an influenza outbreak that was considered to be a pandemic in 2009. The term swine flu came about because the type of influenza virus responsible for the 2009 pandemic, H1N1, contained genetic elements of influenza virus that were mainly thought to be characteristic for influenza strains that caused flu-like symptoms in pigs but had genetically changed to be able to cause flu in humans.

Additionally, another type of swine flu virus, H3N2v, has been discovered. It is not as contagious as H1N1, but there are reports of this virus spreading from pigs to humans. In general, this swine flu is similar in most aspects to the disease caused by H1N1, but it is apparently less severe and is not easily spread from person to person. This article will focus on the swine flu virus H1N1.

Is swine flu (H1N1) contagious?

Swine flu is contagious from person to person. It can be spread through the air by droplets produced by sneezing, coughing, or by direct contact with saliva or mucus secretions. In addition, the virus can survive for a short time outside the infected individual, so people can indirectly contact H1N1 by touching areas (desks, utensils, cups, tabletops, for example) where droplets have recently landed after an infected person with the virus has inadvertently contaminated a surface.

What is the contagious period for swine flu (H1N1)?

The contagious period for H1N1 is about one day before symptoms develop to about a week after symptoms develop in individuals who spontaneously overcome the infection. In severely infected people and in some children, some contagious viruses may be shed for a few weeks.

How will I know if I have swine flu?

Symptoms of swine flu (H1N1) begin like regular flu symptoms and include fever, sore throat, cough, body aches, headaches, chills, and fatigue. Some individuals may also have diarrhea and vomiting. The majority of people with swine flu are not diagnosed definitively with tests. Unfortunately, these symptoms can be similar to those produced by other diseases so usually a person finds out that they have swine flu (H1N1) after contacting their physician, who can run several different blood tests and other viral identification tests to determine what type of flu or other illness may be present. The tests are usually run on those with more severe symptoms.

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Swine Flu (H1N1) Treatment

Two antiviral agents have been reported to help prevent or reduce the effects of swine flu. They are zanamivir (Relenza) and oseltamivir (Tamiflu), both of which are also used to prevent or reduce influenza A and B symptoms.

How is swine flu transmitted?

Swine flu (H1N1) is spread by person-to-person contact by either touching surfaces contaminated by an infected person or by encountering expelled droplets produced when a person is coughing or sneezing. Consequently, swine flu is spread both directly and indirectly by infected individuals to others. However, the spread of swine flu is not 100% effective, as researchers have suggested that people living in the same house with someone infected by the H1N1 virus will have only an 8%-19% chance of getting infected.

How will I know if I am cured of swine flu?

The majority of people who get swine flu (H1N1) spontaneously "cure" themselves with their effective immune response. Others may benefit from the use of antiviral medications and/or supportive therapy, which can include hospitalization for those patients who have severe infections. Unfortunately, even though individuals can be cured of a specific viral type, influenza viruses (including ones that fall into the general category of swine flu viruses) mutate fairly rapidly so that immune protection against one viral type does not mean that a person will be fully or even partially protected against other influenza virus types. This is the reason that each year a new vaccine is typically produced for the flu season that is designed to protect vaccinated people against the predominant influenza types expected to be present in the population.

When should I contact a medical caregiver about swine flu (H1N1)?

Most people who become infected with H1N1 viruses do not need to contact a medical caregiver because the symptoms abate and the infected individual recovers over a period of about a week or so. However, if the symptoms become serious (for example, the patient's symptoms worsen), it is important to contact a physician urgently or possibly emergently. Anyone with symptoms of shortness of breath, confusion, rapid breathing, reduced responsiveness, or bluish skin (especially in children) should be taken to an emergency department.

Those with suppressed immune function, those who have multiple medical problems, or who are pregnant and suspect they have become infected with swine flu (H1N1) should contact their physician immediately. If they have any of the more severe symptoms listed above, they should consider going to an emergency department.

Medically reviewed by Robert Cox, MD; American Board of Internal Medicine with subspecialty in Infectious Disease

REFERENCE:

"Information on Swine Influenza/Variant Influenza Virus." Centers for Disease Control and Prevention. Updated Aug 23, 2016.

Last Editorial Review: 11/8/2016

Reviewed on 11/8/2016
References
Medically reviewed by Robert Cox, MD; American Board of Internal Medicine with subspecialty in Infectious Disease

REFERENCE:

"Information on Swine Influenza/Variant Influenza Virus." Centers for Disease Control and Prevention. Updated Aug 23, 2016.

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