Interim Guidance on Infection Control and Antiviral Recommendations for Patients with Confirmed or Suspected Swine Influenza A Virus Infection

April 20, 2009

Background

Sporadic swine influenza A virus (SIV) infection of humans may produce a wide range of clinical signs and symptoms. Many human cases of SIV infection have had a history of recent direct physical contact with pigs prior to illness onset. However, close (within 6 feet), but not direct contact with pigs, also has been reported among human SIV cases. Limited, non sustained human-to-human SIV transmission has been documented in the published literature. In addition, some confirmed SIV cases have not had a history of exposure to pigs.

Although uncomplicated influenza-like illness (fever, cough or sore throat) has been reported in many cases, mild respiratory illness (nasal congestion, rhinorrhea) without fever and occasional severe disease also has been reported. Other symptoms reported with SIV infection include vomiting, diarrhea, myalgia, headache, chills, fatigue, and dyspnea. Conjunctivitis is rare, but has been reported. Severe disease (pneumonia, respiratory failure) and fatal outcomes have been reported with SIV infection. The potential for exacerbation of underlying chronic medical conditions or invasive bacterial infection with SIV infection should be considered.

This document provides interim guidance on infection control, antiviral treatment and chemoprophylaxis, and monitoring of close contacts of cases of swine influenza virus infection, including guidance for health care workers and public health personnel. The guidance will be updated as needed.

Interim Recommendations

For clinical care or collection of respiratory specimens from a symptomatic individual (acute respiratory symptoms with or without fever) who is a confirmed case, or a suspected case (ill close contact of a confirmed case) of swine influenza A virus infection:

Infectious Period

Persons with swine influenza virus infection should be considered potentially contagious for up to 7 days following illness onset. Persons who continue to be ill longer than 7 days after illness onset should be considered potentially contagious until symptoms have resolved. Children, especially younger children, might potentially be contagious for longer periods. The duration of infectiousness might vary by SIV strain.

Case definitions

A confirmed case of swine influenza virus infection (SIV) is defined as a person with an acute respiratory illness with laboratory confirmed SIV at CDC by one or more of the following tests:

1. real-time RT-PCR
2. viral culture
3. four-fold rise in SIV specific neutralizing antibodies

A suspected case of SIV is defined as a person with an acute respiratory illness who was a close contact to a confirmed case of SIV infection while the case was ill, or is an acutely ill person (acute respiratory illness) with a recent history of contact with an animal with confirmed or suspected SIV infection.

Close contact is defined as: within about 6 feet of an ill person who is a confirmed case of swine influenza A virus infection

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)

Recommendations for Public Health Personnel

For interviews of healthy individuals (i.e. without a current respiratory illness), including close contacts of cases of confirmed swine influenza virus infection, no personal protective equipment or antiviral chemoprophylaxis is needed. See section on antiviral chemoprophylaxis for further guidance.

For interviews of an ill, suspected or confirmed SIV case, the following is recommended:

1. Keep a distance of at least 6 feet from the ill person; or
2. Personal protective equipment: fit-tested N95 respirator [if unavailable, wear a medical (surgical mask)].

For collecting respiratory specimens from an ill confirmed or suspected SIV case, the following is recommended:

1. Personal protective equipment: fit-tested disposable N95 respirator [if unavailable, wear a medical (surgical mask)], disposable gloves, gown, and goggles.
2. When completed, place all PPE in a biohazard bag for appropriate disposal.
3. Wash hands thoroughly with soap and water or alcohol-based hand gel.

Infection Control

Recommended Infection Control for a non-hospitalized patient (ER, clinic or home visit):

1. Separation from others in single room if available until asymptomatic. If the ill person needs to move to another part of the house, they should wear a mask. The ill person should be encouraged to wash hands frequently and follow respiratory hygiene practices. Cups and other utensils used by the ill person should be thoroughly washed with soap and water before use by other persons.

Recommended Infection Control for a hospitalized patient:

1. Standard, Droplet and Contact precautions for 7 days after illness onset or until symptoms have resolved.
2. In addition, personnel should wear N95 respirators when entering the patient room.
3. Use an airborne infection isolation room (AIIR) with negative pressure air handling, if available; otherwise use a single patient room with the door kept closed.
4. For suctioning, bronchoscopy, or intubation, use a procedure room with negative pressure air handling.

Recommended PPE for personnel providing clinical care to ill individuals:

1. Disposable gown, gloves, goggles, N95 respirator.

Antiviral Treatment

Antiviral treatment for confirmed or suspected ill case of swine influenza virus infection may include either oseltamivir or zanamavir, with no preference given at this time. Recommendations for use of antivirals may change as data on antiviral susceptibilities become available.

Initiate treatment as soon as possible after the onset of symptoms.

Oseltamivir:

1. The treatment dosing recommendation for children who weigh 15 kg or less is 30 mg twice a day. For children who weigh more than 15 kg and up to 23 kg, the dose is 45 mg twice a day. For children who weigh more than 23 kg and up to 40 kg, the dose is 60 mg twice a day. For children who weigh more than 40 kg, the dose is 75 mg twice a day.
2. For ages 13 years and older: 75mg twice a day for five days

Zanamivir:

is an alternative for treatment of influenza in patients aged 7 years and older; dosage varies by age. This drug is not approved for treatment of influenza in children aged <7 years. It is an orally inhaled drug that is administered using a disk inhaler device twice a day for five days.

1. The treatment dosing recommendation for persons aged 7 years and older is 2 inhalations twice a day for five days (2 inhalations of 5mg each twice a day for five days)

Antiviral Chemoprophylaxis

Antiviral chemoprophylaxis (pre-exposure or post-exposure) can be considered for close contacts of a confirmed or highly suspected case of swine influenza virus infection.

Close contact is defined as: within about 6 feet of an ill person who is a confirmed case of swine influenza A virus infection (e.g. post-exposure chemoprophylaxis following unprotected close exposure).

Duration of antiviral chemoprophylaxis is 7 days after the last known exposure

Oseltamivir

Administered by mouth once a day for seven days following the last known exposure; dosage varies by age and weight for children aged 1 year to 12 years (available in suspension, 30mg, 45mg, 75mg capsules)

1. The chemoprophylaxis dosing recommendation for children who weigh less than 15 kg is 30 mg once a day. For those who weigh more than 15 kg and up to 23 kg, the dose is 45 mg once a day. For children who weigh more than 23 kg and up to 40 kg, the dose is 60 mg once a day. For children who weigh more than 40 kg, the dose is 75 mg once a day.
2. For ages 13 years and older: 75 mg once a day for seven days

Zanamivir

Is an alternative for chemoprophylaxis for patients aged 5 years and older; dosage varies by age. It is an orally inhaled drug that is administered using a disk inhaler device.

1. Dosing is 2 oral inhalations once a day for seven days (2 inhalations of 5mg each once a day for seven days)

Follow-up Monitoring of Exposed Close Contacts

Close contacts are defined as persons who were within about 6 feet of the confirmed swine influenza case while the case was ill up to 7 days after the case’s illness onset. Examples include household members, social contacts, public health care workers, medical health care workers, and others.

1. Close contacts should be monitored daily for fever (temp ≥38.0 °C) and/or any respiratory symptoms up to 7 days following the last known exposure to an ill person who is a confirmed case of swine influenza virus infection.
2. Close contacts of an ill person who is a confirmed case of swine influenza virus infection should be educated about the signs and symptoms of swine influenza virus infection and advised to contact public health staff if fever or feverishness or any respiratory tract symptoms occur up to 7 days following the last known exposure to the ill case.