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CDC Interim Guidance for Workers who are Employed at Commercial Swine Farms: Preventing the Spread of Influenza A Viruses, Including the 2009 H1N1 Virus   
CDC Interim Guidance for Workers who are Employed at Commercial Swine Farms: Preventing the Spread of Influenza A Viruses, Including the 2009 H1N1 Virus
CDC Interim Guidance for Workers who are Employed at Commercial Swine Farms: Preventing the Spread of Influenza A Viruses, Including the 2009 H1N1 Virus

November 3, 2009 1:00 PM ET

In April 2009, an outbreak of 2009 H1N1 influenza virus infections were detected in people in North America and then spread around the world. In October 2009, the first case of 2009 H1N1 influenza virus in a pig in the United States was confirmed. Additionally, pig infections with 2009 H1N1 influenza virus have been found in other countries.

This interim guidance is issued with the goal of preventing the spread of this novel virus or any other influenza (flu) virus from people to pigs and from pigs to people. These recommendations are for people who work with pigs in the commercial production (farm) setting. The following interim recommendations are based on what are deemed optimal precautions for protecting workers exposed to pigs with known or suspected flu infection on production premises AND for protecting pigs from people with flu.


Influenza viruses that circulate in pigs are different from the influenza viruses circulating in people. Outbreaks of flu in pigs from swine influenza viruses are common. In addition, pigs are uniquely susceptible to infection with influenza viruses of human, swine, and avian origin. Because of this, pigs also can serve as hosts in which influenza viruses from different species can undergo reassortment if a pig is infected with two or more different strains of influenza virus at the same time. Reassortment is a process in which flu viruses exchange genes during replication. The resultant hybrid flu virus could be highly transmissible among people and/or animals and lead to widespread infections.

The 2009 H1N1 virus that is circulating among humans has been detected in swine in several countries, including the U.S. Keeping this new human strain from entering and spreading among swine herds is important to protect animal health and public health, including the health of swine workers.

Interspecies flu infections between people and pigs are most likely to occur when people are in close proximity to pigs, such as in swine production barns. Minimizing the transmission of flu viruses between live swine and people is in the best interest for public health and animal health.

Recognizing the signs of flu in pigs

People who work with live swine should be trained to recognize the signs and symptoms of flu in pigs. Typically illness is mild and a combination of signs will occur together in infected live swine. Signs of flu in pigs can include any of the following:
  • sudden onset of fever
  • lethargy, lack of alertness
  • going off feed (poor appetite)
  • coughing (barking)
  • discharge from the nose or eyes, eye redness or inflammation
  • sneezing
  • breathing difficulties
  • If pigs exhibit these signs, even mildly, appropriate veterinary care should be provided.
Preventing transmission of influenza viruses from pigs to people

Influenza viruses are thought to spread from infected people and pigs to other people and pigs primarily via large infectious droplets expelled during coughing or sneezing. There also is evidence that influenza viruses can be transmitted through contact with surfaces recently contaminated with influenza viruses. A third possible mode of transmission is via the airborne route where small particulates containing the virus are inhaled. The relative contributions of these three modes of transmission to the spread of influenza virus are not fully understood.

Basic Infection Control to prevent transmission of swine influenza viruses from pigs to people

Hand hygiene should be performed after contact with animals or their environment, equipment and surfaces that are possibly contaminated with influenza viruses, and after removing personal protective equipment (PPE) and/or possibly contaminated clothing. Good hand hygiene should consist of washing with soap and water for 20 seconds or the use of other standard hand-disinfection procedures as specified by state government, industry, or USDA outbreak-response guidelines (see Guidelines for novel H1N1 2009 virus in swine in the United States at http://www.usda.gov/H1N1flu) to limit the possibility of transmission of influenza viruses and other pathogens. Workers should avoid touching or rubbing their eyes, nose, and mouth when working around pigs.

Vaccination of pigs with flu vaccine that is effective against circulating strains might reduce the risk of flu in pigs and possibly reduce the risk of people getting infected with swine influenza viruses. However, because multiple strains of influenza virus might be co-circulating within the U.S. pig population and because flu vaccines in pigs are not 100% effective, vaccination of pigs will not eliminate the risk of human infection from swine flu viruses.

Workers should adhere to recommendations for use of personal protective equipment (PPE).

Personal Protective Equipment (PPE)

Swine workers should be required to wear PPE whenever they might be exposed to live swine possibly infected with swine influenza viruses. Adherence to PPE recommendations might lessen a worker’s exposure to influenza viruses and might reduce the chances of carrying contaminated material outside the barn or worksite. Workers should be provided with appropriate PPE and instructions and training in PPE care and use. PPE should include respirators to reduce inhalation exposure to small particles that might contain influenza viruses1. National Institute for Occupational Safety and Health (NIOSH)-certified respirators are the only type of PPE that has been tested to protect workers from inhalation hazards (see http://www.cdc.gov/niosh/npptl/topics/respirators/default.html).

Swine workers should adhere to the following practices:
  • Wear protective clothing, preferably disposable outer garments or coveralls that are laundered at work after each use. To minimize risk of heat stress, wear lightweight clothing beneath protective clothing when appropriate.
  • Wear rubber or polyurethane boots that can be cleaned and disinfected or disposable protective shoe covers.
  • Wear disposable gloves made of lightweight nitrile or vinyl or heavy duty rubber work gloves that can be disinfected.
  • To protect against dermatitis, which can occur from prolonged exposure of the skin to moisture in gloves caused by perspiration, wear a thin cotton glove inside the external glove.
  • Change gloves if they are torn or otherwise damaged.
  • Remove gloves promptly after use, before touching non-contaminated items or environmental surfaces.
  • Take off disposable gloves by turning them inside out over the hand and placed in the trash after use.
  • Wash hands after gloves and other PPE are removed.
  • Wear safety goggles to protect the mucous membranes of eyes.Wear disposable NIOSH-certified filtering facepiece respirators (e.g., N-95, P-100 or N-100 filtering facepiece respirators) that are the minimum level of respiratory protection. This level or higher respiratory protection might already be in use in swine operations due to other hazards that exist in the environment (e.g., dusts). Workers must be fit tested to the respirator model that they will wear and also know how to check the facepiece-to-face seal. Workers who cannot wear a disposable NIOSH-certified filtering face piece respirator because of facial hair or other fit limitations should wear a loose-fitting (i.e., helmeted or hooded) powered air purifying respirator (PAPR) equipped with high-efficiency filters.
  • Wear disposable, lightweight head or hair covers to prevent contamination of hair if shower-out facilities are unavailable.
  • Discard disposable PPE properly, as well as clean and disinfect non-disposable PPE as specified in state government, industry, or USDA outbreak-response guidelines (e.g. non-disposable clothing should be laundered daily or after each use).
  • Enforce biosecurity measures and practices to prevent the introduction of infectious agents from one swine housing unit to another. More information on disinfectant use for influenza viruses can be found at http://www.epa.gov/oppad001/influenza-disinfectants.html
  • Shower-out, if facilities are available, into a clean area at the completion of an employee’s shift. If these facilities are not available, workers should change into clean clothes after their shift. Launder work clothes at the site or place in a plastic bag for washing separately from non–work family laundry.
  • Wash hands thoroughly for 20 seconds with soap and water after removal of any PPE and/or contact with infected animals or possibly contaminated surfaces.
  • 1 Respirators should be used in the context of a comprehensive respiratory protection program as required by the Occupational Safety and Health Administration’s Respiratory Protection standard (29 CFR 1910.134). This includes training, medical evaluation, and fit-testing to ensure appropriate selection and use of NIOSH-certified respirators. To be effective, respirators must provide a proper sealing surface on the wearer’s face. Detailed information on respiratory protection programs is provided at www.osha.gov/SLTC/etools/respiratory and www.cdc.gov/niosh/npptl/topics/respirators.
Surveillance and Monitoring of Workers’ Health

Instruct workers to watch for flu-like symptoms for 7 days after exposure to pigs that are suspected or known to be ill with influenza. The symptoms of 2009 H1N1 flu and illness caused by endemic swine flu viruses in people are similar to the symptoms of seasonal flu. These symptoms in humans can include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills and fatigue. Some people who have been infected with the 2009 H1N1 virus or with swine influenza viruses also have reported diarrhea and vomiting.

Employers should consider making arrangements for appropriate medical follow up and treatment so that ill workers can take the following steps:
  • Notify their supervisor and their employer’s health and safety representative that they are ill.
  • Seek medical care
  • The employer should arrange for health care and should notify the health care provider of the worker’s exposure to swine.
  • The medical care provider will decide if testing or treatment is needed. Tests could include a nasal swab which is best to do within the first 4-5 days of getting sick to be most likely to accurately diagnose influenza.
  • Avoid travel and limit their contact with other people and pigs as much as possible. Stay home for 7 days after symptoms begin or until they have been symptom-free for 24 hours, whichever is longer, except to seek medical care or other necessities.
  • Practice good respiratory and hand hygiene to lower the risk of transmission of virus to others.
  • Cover mouth and nose with a tissue when coughing or sneezing and put used tissue in a waste basket.
  • If tissues are not available, cough or sneeze into their upper sleeve.
  • Always wash hands after coughing or sneezing.
  • More information about appropriate respiratory and hand hygiene is available on CDC’s “Cover Your Cough” website at www.cdc.gov/flu/protect/covercough.htm.
  • Clinicians taking care of patients who have symptoms consistent with influenza and who had exposure to pigs should consult with their local or state health department to coordinate testing for influenza. Information on testing for influenza can be found at http://www.cdc.gov/h1n1flu/specimencollection.htm
Persons at higher risk for complications from influenza

Certain groups are at increased risk of becoming severely ill with influenza. These groups include children younger than 5 years (but especially children younger than 2 years), persons 65 years and older, and pregnant women. Also included are persons of any age who have certain medical conditions such as chronic pulmonary disease, including asthma, or cardiovascular, hepatic, hematologic, neurologic, or metabolic disorders, such as diabetes, and persons who are immunosuppressed (including those immunosuppressed because of medications or HIV). Individuals in these groups can choose to request temporary reassignment to lower-risk tasks to avoid direct animal contact during outbreaks of suspected or confirmed influenza in swine herds.

Administration of influenza antiviral drugs

Antiviral treatment and chemoprophylaxis guidance can be found at http://www.cdc.gov/h1n1flu/recommendations.htm. Influenza antiviral medications can be used for treatment of influenza, including that caused by 2009 H1N1 virus and endemic swine flu viruses.

Antiviral chemoprophylaxis can be considered for workers in direct contact with pigs confirmed to have influenza. Chemoprophylaxis consists of taking an antiviral drug daily for the duration of time the worker is exposed to sick pigs, and for 5-7 days after the last known exposure.

For antiviral treatment or chemoprophylaxis for 2009 H1N1 virus, either oseltamivir or zanamivir are recommended. Because of resistance, amantadine and rimantadine are not recommended.

Antiviral dosing and schedules recommended for 2009 H1N1 virus infection and other influenza viruses can be found at http://www.cdc.gov/flu/professionals/antivirals/dosagetable.htm#table.

Preventing spread of flu virus from workers to pigs

Seasonal flu viruses are occasionally transmitted from people to pigs and rare cases of infection in pigs have been documented. Additionally, transmission of 2009 H1N1 virus from people to pigs has occurred. Therefore, workers should be educated on the need to prevent the spread of influenza viruses from people to pigs. Workers also should be trained to recognize flu-like symptoms in humans. These symptoms include fever, cough, sore throat, runny or stuffy nose, body aches, headache, chills, fatigue, and possibly vomiting or diarrhea. A worker who has been diagnosed with flu, has flu-like symptoms, or reports contact with others who have flu-like symptoms should avoid contact with pigs (listed above). If the worker is essential to the operation and must enter the facilities, enforce their use of properly fitted, valve-less N95 respirators, gloves and other personal protective equipment (PPE) while on the farm. Biosecurity measures and practices (e.g. shower-in/shower-out procedures, PPE, disinfectant footbaths) to prevent the introduction of infectious agents into a swine operation also should be enforced. Biosecurity recommendations for pork producers from the National Pork Board can be found at http://www.pork.org/documents/News/Novel%20H1N1%20Biosecurity%20Recommendations%20for%20Producers%20v2.pdf

Vaccination of Swine Workers with Influenza Vaccine

Employers should consider providing swine workers with access to immunizations that follow the recommendations for the general public for seasonal influenza vaccine (see http://www.cdc.gov/flu/protect/vaccine/index.htm). Persons at higher risk for complications from influenza infection (listed above) and household contacts of those persons should receive annual seasonal influenza vaccination. Any worker who has contact with pigs should be offered seasonal flu vaccine; this will decrease their risk of passing seasonal flu viruses to pigs. Seasonal influenza vaccination of workers might decrease the potential for people or pigs to become co-infected with both human and swine flu viruses. Such dual infections could result in reassortment of the two different viruses and lead to a new influenza virus that has a different combination of genes.

The seasonal influenza vaccine is unlikely to provide protection against 2009 H1N1 virus infection. However, initial doses of 2009 H1N1 vaccine are currently available. The 2009 H1N1 vaccine is not intended to replace the seasonal flu vaccine -- it is intended to be used along-side the seasonal flu vaccine. Currently, the only occupational groups prioritized for initial doses of the 2009 H1N1 vaccine are health care and emergency medical services personnel (see http://www.cdc.gov/h1n1flu/vaccination/acip.htm). Swine workers should contact their local or state health department regarding 2009 H1N1 vaccination plans and availability of vaccine.

Additional Resources
CDC Website: http://www.cdc.flu.gov/
USDA Website: http://www.usda.gov/H1N1flu
National Pork Board Website: http://www.pork.org/NewsAndInformation/H1N1Update.aspx?id=629
Guidance for people who work with pigs in non-commercial settings:

Posted on 11/3/2009 (Archive on 11/24/2009)
Posted by hspalding  Contributed by

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