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According to information from the Centers for Disease Control and Prevention (CDC):

"The estimated incubation period... could range from 1-7 days, and more likely 1-4 days.

"The typical incubation period for influenza is 1-4 days (average: 2 days). Adults shed influenza virus from the day before symptoms begin through 5-10 days after illness onset. However, the amount of virus shed, and presumably infectivity, decreases rapidly by 3-5 days after onset in an experimental human infection model. Young children also might shed virus several days before illness onset, and children can be infectious for 10 or more days after onset of symptoms. Severely immunocompromised persons can shed virus for weeks or months.

"Uncomplicated influenza illness typically resolves after 3-7 days for the majority of persons, although cough and malaise can persist for >2 weeks. However, influenza virus infections can cause primary influenza viral pneumonia; exacerbate underlying medical conditions (e.g., pulmonary or cardiac disease); lead to secondary bacterial pneumonia, sinusitis, or otitis media; or contribute to coinfections with other viral or bacterial pathogens."

Other responses from WikiAnswerers:

  • Studies are continuing to determine the specific incubation period of the 2009 Swine Flu outbreak, but opinions of slight variations in the estimates are surfacing. For now, however, the official CDC information is as quoted above.
  • Infected people may be able to pass on the flu to someone else ("shed virus") before they know they are sick, while they are sick, and for varying time periods after feeling well again.
  • People with swine influenza virus infection should be considered potentially contagious as long as they are symptomatic and possibly for up to 7 days following illness onset. Children, especially younger children, might potentially be contagious for longer periods.
  • Some viruses and bacteria can live 2 hours or longer on surfaces like cafeteria tables, doorknobs, and desks. Frequent hand washing will help you reduce the chance of getting contamination from these common surfaces. Don't go to public places if you have the flu symptoms.
  • For treatment, antiviral drugs work best if started soon after getting sick (within 2 days of symptoms).
  • This virus has the same properties in terms of spread as seasonal flu viruses. With seasonal flu, studies have shown that people may be contagious from one day before they develop symptoms to up to 7 days after they get sick. Children, especially younger children, might potentially be contagious for longer periods.

Update 9/27/09

A Department of Homeland Security (DHS) report from 9/19/09 indicates that the period of infectivity of A-H1N1/09 is longer than originally believed, and longer than that of the seasonal flu.

Studies on how long a person remains contagious back up the previously reported CDC guidelines that one should be suspected to be capable of spreading the Novel Swine Flu for one full week after the symptoms start or until 24 hours after the fever subsides [while taking no fever reducers] which ever is longer, rather than the most recent CDC guidelines that waiting for 24 hours after fever subsides without taking fever reducers is long enough.

In fact, the best determination can probably be made by how long the cough lasts.

The studies show that in some cases the virus remains in the nasal passages of patients for up to 16 days after symptoms begin. Below are some excerpts from the report:

"Swine flu also appears to be contagious longer than ordinary seasonal flu, several experts said.

When the coughing stops is probably a better sign of when a swine flu patient is no longer contagious, experts said after seeing new research that suggests the virus can still spread many days after a fever goes away.

Using a very sensitive test to detect virus in the nose or throat, [the study] found that 80 percent had it five days after symptoms began, and 40 percent seven days after. Some still harbored virus as long as 16 days later. How soon they started on antiviral medicines such as Tamiflu made a difference in how much virus was found, but not whether virus was present at all. . .

Doctors know that people can spread ordinary seasonal flu for a couple of days before and after symptoms start by studying virus that patients shed in mucus. The first such studies of swine flu are just coming out now, and they imply a longer contagious period for the novel bug. "

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โˆ™ 2015-07-25 17:55:11
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Q: How long is the incubation period and each stage of a swine flu infection?
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If you were in Mexico three weeks ago and are still feeling good are you uninfected from the Swine Flu?

The incubation period of swine flu is 5 to 7 days. If you were actually were exposed 21 days ago, then you are past the incubation time for symptoms to begin occurring from that exposure.

Can Swine Flu be spread by someone who is not sick?

Yes, people can be infectious with the swine flu and other viruses one to two days before their symptoms are obvious. See the related question below about the incubation period of swine flu.

How fast does swine flu spread from person to person?

Incubation is 48-72 hours.

Who discovered swine influenza?

swine flu is an infection caused by pigs or swines

Is Swine Flu contagious during the incubation stage?

It appears to be generally accepted that a person infected with swine flu may be contagious for one day prior to the appearance of any symptoms; you will be infectious before you know that you are ill.See the related question below for additional information.

How many days does it take swine to spread inside your body?

Since this question is placed in the flu category, the assumption is that you're asking how fast the swine fluspreads inside your body. For specifics about this process of the lytic cycle of the influenza virus, see the related question about how long the incubation period and all the steps of a flu infection are for the swine flu, which is in the related questions section for this Q&A.On the lighter side:A swine (a pig) is too big to fit inside most human bodies, and they are none too pleased if you try.

Do you cough and sneeze when you have a sinus infection?


If you had swine flu 7 days ago and now are going to be looking after a child can you give him the swine flu?

If you have been symptom free for seven days, then you should no longer be spreading viruses. See the related question below for more information about the incubation period and stages of this influenza.

Does the swine flu shot help you?

Yes, it's a vaccination that helps you prevent the swine flu infection.

Is the swine flue a fungus?

No, it is a virus infection! that is why it is called a flu.

Do you get spots if you get Swine Flu?

No you don't unless you have a secondary infection.

Should you go to school if you have Swine Flu?

NO. Swine Flu is highly contageous in all but the last day or so of infection. SO NO.

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