MCHD Health Advisory No. 3

Print
Press Enter to show all options, press Tab go to next option

Swine Influenza - Testing, Reporting & Management of Cases

Montgomery County Department of Health (MCHD) is working closely with the Pennsylvania Department of Health to identify and track suspected and confirmed cases of swine flu in the County. To assist with case recognition and surveillance, MCHD would like to provide the following recommendations. Additional information is available on the website for the Centers for Disease Control and Prevention (CDC) (www.cdc.gov/swineflu); the website for the Pennsylvania Department of Health (www.state.pa.us); or the MCHD website (www.health.montcopa.org).

Testing for Swine Influenza A (H1N1) Virus

All persons who have clinical symptoms and epidemiologic exposure (travel to affected areas or contact with persons who traveled to affected areas) should have upper respiratory specimens collected to test for swine influenza A (H1N1) virus. Screening of asymptomatic travelers is not recommended.

Preferred Respiratory Specimens

The following should be collected as soon as possible after illness onset: nasopharyngeal swab/aspirate or nasal wash/aspirate. If these specimens cannot be collected, a combined nasal swab with an oropharyngeal swab is acceptable. For patients who are intubated, an endotracheal aspirate should also be collected. Specimens should be placed into sterile viral transport media (VTM) and immediately placed on ice or cold packs or at 4°C (refrigerator) for transport to the laboratory. Recommended infection control guidance is available for persons collecting clinical specimens and for laboratory personnel.

Swabs

Ideally, swab specimens should be collected using swabs with a synthetic tip (e.g., polyester or Dacron®) and an aluminum or plastic shaft. Swabs with cotton tips and wooden shafts are not recommended. Specimens collected with swabs made of calcium alginate are not acceptable. The swab specimen collection vials should contain 3ml of viral transport medium (e.g., containing, protein stabilizer, antibiotics to discourage bacterial and fungal growth, and buffer solution), such as M4RT or the BD Universal Viral Transport System.

Storing Clinical Specimens

All respiratory specimens should be kept at 4°C until they can be placed at -70°C. If a -70°C freezer is not available, specimens should be kept at 4°C, preferably no longer than 1 week.

Shipping Clinical Specimens

Clinical specimens should be shipped on dry ice in appropriate packaging.
All specimens should be labeled clearly and include information requested by the laboratory. Suspect case specimens shipped from the state public health laboratory to CDC should include all information required for seasonal influenza surveillance isolate or specimen submission.

Recommended Tests

Real-time RT-PCR for influenza A, B, H1, H3 at a State Health Department Laboratory is recommended. Currently, swine influenza A (H1N1) virus will test positive for influenza A and negative for H1 and H3 by real-time RT-PCR. If reactivity of real-time RT-PCR for influenza A is strong (e.g., Ct <30) it is more suggestive of a novel influenza A virus. Confirmation as swine influenza A (H1N1) virus is performed at CDC currently, but may be available in state public health laboratories soon.

Other Influenza Tests

Rapid Influenza Antigen Test

Some commercially available rapid tests can distinguish between influenza A and B viruses. A patient with a positive rapid test for influenza A may meet criteria for a probable case (see above). These tests have unknown sensitivity and specificity to detect human infection with swine influenza A (H1N1) virus in clinical specimens, and have suboptimal sensitivity to detect seasonal influenza viruses. Therefore, a negative rapid test could be a false negative and should not be assumed a final diagnostic test for swine influenza infection.

Immunofluorescence (DFA or IFA)

These tests can distinguish between influenza A and B viruses. A patient with a positive for influenza A by immunofluorescence may meet criteria for a probable case (see above). Immunofluorescence depends upon the quality of a clinical specimen, operator skills, and has unknown sensitivity and specificity to detect human infection with swine influenza A (H1N1) virus in clinical specimens. Therefore, a negative immunofluorescence could be a false negative and should not be assumed a final diagnostic test for swine influenza infection.

Viral Culture

Isolation of swine influenza A (H1N1) virus is diagnostic of infection, but may not yield timely results for clinical management. A negative viral culture does not exclude infection with swine influenza A (H1N1) virus.

Reporting of Cases

MCHD is encouraging clinicians to report all suspected and confirmed cases of swine influenza. During normal business hours, please call 610-278-5117. After normal business hours, call Montgomery County Police Radio at 610-275-1222 and ask to speak to the person on-call for the Health Department.

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 at CDC by one or more of the following tests;

  1. real-time RT-PCR
  2. viral culture

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.

Management of Cases in the Community

Persons who are suspected or confirmed to have swine influenza infection should be strongly encouraged to self-isolate in their home for 7 days after the onset of illness, or at least 24 hours after symptoms have resolved, whichever is longer.

Persons who experience febrile respiratory illness and wish to seek medical care should contact their healthcare providers to report illness (by telephone or some other remote means) before seeking care at a clinic, physician’s office or hospital.

Persons in home isolation should be counseled regarding infection control within the home:

  • Ill persons and contacts should be instructed re: frequent hand washing with soap and water.
  • Ill persons and contacts should be instructed re: the use of alcohol-based hand gels when soap and water are not available and hands are not visibly dirty.
  • Ill persons should cover coughs and sneezes, and possibly wear a face mask when within 6 feet of others in the home.
  • Ill persons should try to confine themselves to a room separate from common areas of the house and use a separate bathroom if possible.
  • Ill persons should have only one caregiver to minimize exposure to household members. Caregivers should minimize the amount of time spent in close contact and consider wearing a face mask (surgical mask) or N95 respirator. These are available at most drugstores, hardware or medical supply stores.
  • Used tissues should be disposed in the trash; hands should be washed after touching used tissues and similar waste.
  • Wipe down high-touch surfaces (used by the ill persons) with a household disinfectant.
  • Linens, eating utensils and dishes should not be shared with the ill person.

Close contacts to cases, particularly household contacts, are at high risk for acquiring infection. They should be advised of this risk. They should be advised to:

  • Remain home at the earliest sign of illness.
  • Minimize contact in the community to the extent possible.
  • Designate a single household family member as the ill person’s caregiver to minimize interactions with asymptomatic persons.
  • Contact their healthcare provider at the earliest onset of symptoms, to ensure that they receive treatment with antiviral medication.

Antiviral Medication Usage

Empiric antiviral treatment is recommended for any ill person suspected to have swine influenza infection.

Recommended duration of treatment is 5 days. (Note that clinically available antiviral medications have not been approved for use in pregnant women.)

Laboratory testing on these swine influenza A (H1N1) viruses indicate that they are susceptible (sensitive) to oseltamivir and zanamivir.

Antiviral chemoprophylaxis (pre-exposure or post-exposure) with either oseltamivir or zanamavir is recommended for the following individuals:

  • Household close contacts 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.
  • 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.
  • Recent travelers to Mexico who are at high-risk for complications of influenza (persons with certain chronic medical conditions, elderly).
  • Healthcare workers or public health workers who had unprotected close contact with an ill confirmed case of swine influenza virus infection during the case’s infectious period.

Antiviral chemoprophylaxis (pre-exposure or post-exposure) with either oseltamivir or zanamavir can be considered for the following individuals:

  • Any healthcare 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 cases, and who is caring for patients with acute febrile respiratory illnesses.

Duration of antiviral chemoprophylaxis is 7 days after the last known exposure to an ill confirmed case of swine influenza infection. Antiviral dosing and schedules recommended for chemoprophylaxis of swine influenza A virus infection are the same as those recommended for seasonal influenza:

http://www.cdc.gov/flu/professionals/antivirals/dosagetable.htm#table

Additional infection control measures and guidance documents, including those specific to healthcare workers, may be found at: www.cdc.gov/swineflu

MCHD is encouraging clinicians to report all suspected and confirmed cases of swine influenza. During normal business hours, please call 610-278-5117. After normal business hours, call Montgomery County Police Radio at 610-275-1222 and ask to speak to the person on-call for the Health Department.