Guideline Swine Flu

What is swine influenza?
Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs. Swine flu viruses cause high levels of illness and low death rates in pigs...read more

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Guidance for Clinicians & Public Health Professionals

What is swine influenza?

Swine Influenza (swine flu) is a respiratory disease of pigs caused by type A influenza virus that regularly causes outbreaks of influenza in pigs. Swine flu viruses cause high levels of illness and low death rates in pigs. Like all influenza viruses, swine flu viruses change constantly. Pigs can be infected by avian influenza and human influenza viruses as well as swine influenza viruses. When influenza viruses from different species infect pigs, the viruses can reassort (i.e. swap genes) and new viruses that are a mix of swine, human and/or avian influenza viruses can emerge. Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 viruses.

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Can swine flu infect humans?

Swine flu viruses do not normally infect humans. However, sporadic human infections with swine flu have occurred. Most commonly, these cases occur in people with direct exposure to pigs (e.g. children near pigs at a fair or workers in the swine industry). In addition, there have been documented cases of persons spreading swine flu to others.

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How does it spread?

Spread of this swine influenza A (H1N1) virus is thought to be happening in the same way that seasonal flu spreads. Flu viruses are spread mainly from person to person through coughing or sneezing of people with influenza. Sometimes people may become infected by touching something with flu viruses on it and then touching their mouth or nose.

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What is considered as the "infectious period"?

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.

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How many cases of swine influenza have been reported worldwide?

The current situation regarding the outbreak of swine influenza A (H1N1) is evolving rapidly. As of 27th April 2009, the United States Government has reported 40 laboratory confirmed human cases of swine influenza A (H1N1), with no deaths. Mexico has reported 26 confirmed human cases of infection with the same virus, including seven deaths. Canada has reported six cases, with no deaths, while Spain has reported one case, with no deaths and Scotland has reported 2 cases.

On the advice of the Emergency Committee of the World Health Organization, the Director General has raised the level of influenza pandemic alert, indicating the likelihood of a pandemic has increased, but not that a pandemic is inevitable.

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Are there any travel restrictions issued by the WHO?

WHO has not issued any travel restrictions or border closures; however, the agency recommends people who are ill to delay international travel and for people developing symptoms following international travel to seek medical attention. In addition, the CDC recommends forgoing any nonessential travel to Mexico.

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What are the clinical features of swine flu in humans?

Swine influenza A virus infection (swine flu) can cause a wide range of symptoms, including fever, cough, sore throat, body aches, headache, chills and fatigue. Some people have reported diarrhea and vomiting associated with swine flu.

Like seasonal flu, swine flu in humans can vary in severity from mild to severe. Severe disease with pneumonia, respiratory failure and even death is possible with swine flu infection. Certain groups might be more likely to develop a severe illness from swine flu infection, such as persons with chronic medical conditions. Sometimes bacterial infections may occur at the same time as or after infection with influenza viruses and lead to pneumonias, ear infections, or sinus infections.

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How can one diagnose swine flu?

Clinicians should consider the possibility of swine influenza virus infections in patients presenting with febrile respiratory illness.

If swine flu is suspected, clinicians should obtain a respiratory swab for swine influenza testing and place it in a refrigerator (not a freezer). Once collected, the clinician should contact their state or local health department to facilitate transport and timely diagnosis at a state public health laboratory.

Case Definitions for Infection with Swine Influenza A (H1N1) Virus
A confirmed case of swine influenza A (H1N1) virus infection is defined as a person with an acute febrile respiratory illness with laboratory confirmed swine influenza A (H1N1) virus infection by one or more of the following tests:

  1. real‐time RTPCR (real time‐ polymerase chain reaction)
  2. viral culture

Infectious period
The infectious period for a confirmed case of swine influenza A (H1N1) virus infection is defined as 1 day prior to the case's illness onset to 7 days after onset. A probable case of swine influenza A (H1N1) virus infection is defined as a person with an acute febrile respiratory illness who is:

• positive for influenza A, but negative for H1 and H3 by influenza RT‐PCR, or
• positive for influenza A by an influenza rapid test or an influenza immunofluorescence
assay (IFA) plus meets criteria for a suspected case
A suspected case of swine influenza A (H1N1) virus infection is defined as a person with acute
febrile respiratory illness with onset
• within 7 days of close contact with a person who is a confirmed case of swine
influenza A (H1N1) virus infection, or
• within 7 days of travel to community either within the United States or internationally where there are one or more confirmed swine influenza A(H1N1) cases, or
• resides in a community where there are one or more confirmed swine influenza cases.

Close contact is defined as: within about 6 feet of an ill person who is a confirmed or suspected
case of swine influenza A (H1N1) virus infection during the case’s infectious period.
Acute respiratory illness is defined as: recent onset of at least two of the following: rhinorrhea
or nasal congestion, sore throat, cough (with or without fever or feverishness)
Highrisk group for complications of influenza is defined as: a person who is at high‐risk for
complications of seasonal influenza: However, it too early to ascertain what persons are at
high‐risk for complications of swine influenza A(H1N1) virus infection.
Clinicians should consider swine influenza A (H1N1) virus infection in the differential diagnosis
of patients with febrile respiratory disease and who
• live in areas in the U.S. with confirmed human cases of swine influenza A (H1N1) virus
infection or
• who traveled recently to Mexico or were in contact with persons who had febrile
respiratory illness and were in the areas of the U.S. with confirmed swine influenza

cases or Mexico in the 7 days preceding their illness onset.

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What steps should be taken for Infection Control of Ill Persons in a Healthcare Setting?

Patients with suspected or confirmed case‐status should be placed in a singlepatient room with the door kept closed. If available, an airborne infection isolation room (AIIR) with negative pressure air handling with 6 to 12 air changes per hour can be used. Air can be exhausted directly outside or be re‐circulated after filtration by a high efficiency particulate air (HEPA) filter. For suctioning, bronchoscopy, or intubation, use a procedure room with negative pressure air handling.

The ill person should wear a surgical mask when outside of the patient room, and should be encouraged to wash hands frequently and follow respiratory hygiene practices. Cups and other utensils used by the ill person should be washed with soap and water before use by other persons. Routine cleaning and disinfection strategies used during influenza seasons can be applied to the environmental management of swine influenza.

Standard, Droplet and Contact precautions should be used for all patient care activities, and maintained for 7 days after illness onset or until symptoms have resolved. Maintain adherence to hand hygiene by washing with soap and water or using hand sanitizer immediately after removing gloves and other equipment and after any contact with respiratory secretions. Personnel providing care to or collecting clinical specimens from suspected or confirmed cases should wear disposable nonsterile gloves, gowns, and eye protection (e.g., goggles) to prevent conjunctival exposure.

What should be the advice for caring of an infected person at home?

• Stay home for 7 days after the start of illness and fever is gone
• Get plenty of rest
• Drink clear fluids (such as water, broth, sports drinks, electrolyte beverages for infants) to keep from being dehydrated
• Cover coughs and sneezes. Clean hands with soap and water or an alcohol‐based hand rub often and especially after using tissues and after coughing or sneezing into hands.
• Avoid close contact with others – do not go to work or school while ill
• Be watchful for emergency warning signs (see below) that might indicate you need to seek medical attention

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When to Seek Emergency Medical Care?

Get medical care right away if the sick person at home:
• has difficulty breathing or chest pain
• has purple or blue discoloration of the lips
• is vomiting and unable to keep liquids down
• has signs of dehydration such as dizziness when standing, absence of urination, or in infants, a lack of tears when they cry
• has seizures (for example, uncontrolled convulsions)
• is less responsive than normal or becomes confused
• Keep the sick person in a room separate from the common areas of the house. (For example, a spare bedroom with its own bathroom, if that’s possible.) Keep the sickroom door closed.

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What are the recommendations for the use of antivirals in such situations?

Clinicians should consider treating any person with confirmed or suspected swine influenza with an antiviral drug. CDC recommends the use of neuraminidase inhibitor antiviral medications zanamivir and oseltamivir for the treatment and/or prevention of infection with swine influenza viruses. The swine influenza A (H1N1) virus is sensitive (susceptible) to the zanamivir and oseltamivir. It is resistant to the adamantane antiviral medications amantadine
and rimantadine.
Suspected Cases
Empiric antiviral treatment is recommended for any ill person suspected to have swine influenza A (H1N1) virus infection. Antiviral treatment with either zanamivir alone or with a combination of oseltamivir and either amantadine or rimantadine should be initiated as soon as possible after the onset of symptoms. Recommended duration of treatment is five days. Recommendations for use of antivirals may change as data on anti viral susceptibilities become available.

Antiviraldoses and schedules recommended for treatment of swine influenza A (H1N1) virus infection are the same as those recommended for seasonal influenza

Confirmed Cases
For antiviral treatment of a confirmed case of swine influenza A (H1N1) virus infection, either oseltamivir or zanamivir may be administered. Recommended duration of treatment is five days. These same antivirals should be considered for treatment of cases that test positive for influenza A but test negative for seasonal influenza viruses H3 and H1 by PCR.

Regnant Women
Oseltamivir, zanamivir, amantadine, and rimantadine are all “Pregnancy Category C" medications, indicating that no clinical studies have been conducted to assess the safety of these medications for pregnant women. No adverse effects have been reported among women who received oseltamivir or zanamivir during pregnancy or among infants born to such women. However, both amantadine and rimantadine have been demonstrated in animal studies to be teratogenic and embryotoxic when administered at substantially high doses

Antiviral Chemoprophylaxis
For antiviral chemoprophylaxis of swine influenza A (H1N1) virus infection, either oseltamivir or zanamivir are recommended. Duration of antiviral chemoprophylaxis is 7 days after the last known exposure to an ill confirmed case of swine influenza A (H1N1) virus infection. Antiviral chemoprophylaxis (pre‐exposure or post‐exposure) with either oseltamivir or zanamivir is recommended for the following individuals:
1. Household close contacts who are at high‐risk for complications of influenza (persons with certain chronic medical conditions, elderly) of a confirmed or suspected case.
2. School children who are at high‐risk for complications of influenza (persons with certain chronic medical conditions) who had close contact (face‐to‐face) with a confirmed or suspected case.
3. Travelers to Mexico who are at high‐risk for complications of influenza (persons with certain chronic medical conditions, elderly).
4. Border workers (Mexico) who are at high‐risk for complications of influenza (persons with certain chronic medical conditions, elderly).
5. Health care workers or public health workers who had unprotected close contact with an ill confirmed case of swine influenza A (H1N1) virus infection during the case’s infectious period. Antiviral chemoprophylaxis (pre‐exposure or post‐exposure) with either oseltamivir or zanamivir can be considered for the following:
1. Any health care worker who is at high‐risk for complications of influenza (persons with certain chronic medical conditions, elderly) who is working in an area with confirmed swine influenza A (H1N1) cases, and who is caring for patients with any acute febrile respiratory illness.
2. Non‐high risk persons who are travelers to Mexico, first responders, or border workers who are working in areas with confirmed cases of swine influenza A (H1N1) virus infection.

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