Interim Guidance for Follow-up of Contacts of Persons with Suspected Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus
This guidance provides recommendations for follow-up of contacts of suspected human cases of highly pathogenic avian influenza (HPAI) A (H5N1) virus infection in the United States. The guidance is for public health personnel who are involved in surveillance of contacts of suspected or confirmed cases of H5N1 virus infection in the United States.
Guidance for testing of suspected human cases of HPAI H5N1 virus infection in the United States is available. See Interim Guidance for Laboratory Testing of Persons with Suspected Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus in the United States for more information.
To date, there have been no reports of HPAI H5N1 virus infections among poultry, wild birds, other animals or humans in the United States. This guidance is based upon current knowledge regarding human infection with HPAI H5N1 virus, and will be updated if the epidemiology of human infections with HPAI H5N1 virus changes.
Public health personnel should attempt to identify all known close contacts* of suspected HPAI H5N1 cases (see Interim Guidance for Laboratory Testing of Persons with Suspected Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus in the United States for more information.)
*Close contacts are defined as persons who were within about 6 feet of a suspected, probable or confirmed H5N1 case while the case was symptomatic.
Potential close contacts include the following identifiable persons:
- household and family contacts
- health care personnel
- laboratory workers
- other persons who were known to be within about 6 feet of the suspected case
Available data suggest that the incubation period for human infection with HPAI H5N1 virus is generally ≤7 days. Therefore, all identified close contacts should be monitored daily for 7 days after the last known exposure to an ill person suspected to be infected with HPAI H5N1 virus. The following should be assessed each day during this period:
- measured temperature
- presence of any illness symptoms
Any close contacts that have a measured temperature of ≥38.0°Celsius (≥100.4° F) or any illness symptoms should be referred for prompt medical evaluation, and possible testing for HPAI H5N1 virus infection. While most confirmed human cases of HPAI H5N1 virus infection have experienced fever and respiratory symptoms, some patients have experienced fever and diarrhea or fever and seizures. Asymptomatic close contacts of a suspected case of HPAI H5N1 virus infection do not require quarantine. For guidance on infection control precautions, see the Department of Health and Human Services (HHS) Pandemic Plan (Supplement 4: Infection Control) [173 KB, 22 pages]. Clinicians can consult CDC for specific case-by-case infection control recommendations.
Duration of Follow-up of Close Contacts of a Suspected or Confirmed HPAI H5N1 case
Monitoring of close contacts of a suspected HPAI H5N1 case may be discontinued when laboratory testing by influenza-H5-specific reverse-transcription polymerase chain reaction (RT-PCR) of appropriately collected respiratory specimens from the suspect HPAI H5N1 case at a state health department laboratory or at CDC has excluded infection with HPAI H5N1 virus, or upon the absence of any illness symptoms among contacts at the end of the 7-day surveillance period described above.
Post-exposure Antiviral Chemoprophylaxis for Close Contacts of a Suspected or confirmed HPAI H5N1 case
Post-exposure antiviral chemoprophylaxis with a neuraminidase inhibitor medication (oral oseltamivir or inhaled zanamivir, once daily) should be provided as soon as possible to close contacts of a suspect HPAI H5N1 case if chemoprophylaxis can be started within 2 days of the last known exposure to the suspect HPAI H5N1 case. The recommended duration of antiviral chemoprohylaxis is for 7 days after the last known exposure. Oral oseltamivir is the recommended antiviral medication for chemoprophylaxis of HPAI H5N1 virus infection; inhaled zanamivir is an alternative. Oseltamivir is approved for chemoprophylaxis of influenza in persons aged one year and older; zanamivir is approved for chemoprophylaxis of influenza in persons aged 5 years and older. Physicians should consult the manufacturer’s package insert for dosing, contraindications, and potential adverse effects.
If chemoprophylaxis cannot be started within 2 days of the last known exposure to the suspect HPAI H5N1 case, then antiviral treatment (twice daily) with oseltamivir is recommended for 7 days.
Oseltamivir chemoprophylaxis should be provided to close contacts of a suspected or confirmed HPAI H5N1 case in the following order of priority:
- Highest-risk exposure groups
- Household or close family member contacts of a suspected or confirmed HPAI H5N1 case
- Moderate-risk exposure groups
- Health care personnel in close contact (within about 6 feet) with a suspected or confirmed HPAI H5N1 case (e.g., during intubation or performing tracheal suctioning, or delivering nebulized drugs, or handling inadequately screened/sealed body fluids without use of recommended personal protective equipment (PPE), or with a recognized breach in PPE procedures including improper doffing)
- Laboratory workers who had unprotected exposure to HPAI H5N1 virus-containing samples
- Social contacts of a suspected or confirmed HPAI H5N1 case
- Low-risk exposure groups
- Health care personnel not in close contact with a suspected or confirmed HPAI H5N1 case or who used appropriate PPE during exposure to a suspected or confirmed HPAI H5N1 case
*Note that close contact has been considered to be within 3 feet or 1 meter by infection control professionals. To define a close contact, this document uses “within about 6 feet of an ill person” to include the potential contribution of small particle droplet nuclei and large droplet transmission. (see footnote** below)
When to Discontinue Post-exposure Antiviral Chemoprophylaxis of Close Contacts of a Suspected or confirmed HPAI H5N1 case
Antiviral chemoprophylaxis of close contacts of a suspected HPAI H5N1 case may be discontinued when laboratory testing by influenza-H5-specific RT-PCR of appropriately collected respiratory specimens from the suspected HPAI H5N1 case at a state health department laboratory or at CDC has excluded infection with HPAI H5N1 virus, or absence of any illness symptoms among contacts at the end of the 7-day chemoprophylaxis and monitoring period. Similarly, post-exposure antiviral chemoprophylaxis of close contacts may be discontinued when the above conditions are met.
Symptomatic illness Among Close Contacts of a Confirmed HPAI H5N1 case
A close contact of a confirmed HPAI H5N1 case who experiences any illness signs (fever) or symptoms during the 7-day monitoring period should be isolated immediately and respiratory specimens (see Interim Guidance for Laboratory Testing of Persons with Suspected Infection with Highly Pathogenic Avian Influenza A (H5N1) Virus in the United States) should be collected for HPAI H5N1 virus testing at the state health department as soon as possible. If the patient tests positive for HPAI H5N1 virus and was taking oseltamivir post-exposure chemoprophylaxis or treatment, oseltamivir should be stopped and treatment with inhaled zanamivir (twice daily) should be started as soon as possible; the patient should be hospitalized and isolated, and recommended infection control procedures should be implemented.
When to Contact CDC
The Influenza Division, CDC, should be contacted immediately for any positive results of HPAI H5N1 virus testing, or at any time for any questions related to specimen collection, monitoring, infection control, antiviral chemoprophylaxis or treatment, and laboratory testing. Laboratory results for human clinical specimens that test positive for HPAI H5N1 virus by influenza-H5-specific RT-PCR at a laboratory in the United States should be confirmed as soon as possible at the Influenza Division, National Center for Immunization and Respiratory Diseases, CDC, a designated WHO H5 Reference Laboratory located in Atlanta, Georgia. Before sending specimens, state and local health departments should contact the CDC Influenza Division Epidemiology and Prevention Branch at (404) 639-3747 (Monday – Friday, 8:30 AM - 5:00 PM or the on-call epidemiologist at (770) 488-7100 (all other times).
**Influenza is thought to be primarily transmitted from person-to-person via virus-laden droplets that are generated when infected persons cough or sneeze; these droplets can then settle on the mucosal surfaces of the upper respiratory tracts of susceptible persons who are near (e.g., within about 6 feet) infected persons. Three feet has often been used by infection control professionals to define close contact and is based on studies of respiratory infections; however, for practical purposes, this distance may range up to 6 feet. The World Health Organization defines close contact as "approximately 1 meter;" the U.S. Occupational Safety and Health Administration uses "within 6 feet." For consistency with these estimates, this document defines close contact as a distance of up to approximately 6 feet.