Clinician Brief: Evaluating and Managing Patients Exposed to Animals or Persons Infected with Novel Influenza A Viruses of Public Health Concern

Background

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Novel influenza A viruses are influenza A viruses that have infected people but are antigenically and genetically different from seasonal influenza A viruses currently circulating among humans. Novel influenza A viruses are predominantly of swine or avian origin. Swine influenza A viruses circulate among pigs worldwide. Avian influenza A viruses circulate among wild birds worldwide and can infect domestic poultry and other birds to cause disease referred to as avian influenza. Avian influenza A viruses may also infect other animals such as mammals, including dairy cattle, to cause a wide range of disease.

Some novel influenza A viruses cause high morbidity and mortality in infected poultry, while others cause no illness or only mild disease in poultry. Some novel influenza A viruses have caused sporadic infections in humans resulting in mild to severe illness. These novel influenza A viruses are of public health concern because of their pandemic potential if a virus acquires the ability to cause sustained human-to-human transmission. People with exposure to poultry or wild birds or other animals infected with novel influenza A viruses or associated contaminated environments or materials may become infected with these viruses.

Summary Recommendations

Recommended actions for patients considered to have recent exposure to avian influenza A viruses or other novel influenza A viruses.

If signs/symptoms compatible with novel influenza A virus infection and a history of exposures to animals or to a symptomatic confirmed or probable human case of novel influenza A virus infection are present:

1. Isolate the patient and follow the infection control recommendations below.
2. Initiate empiric antiviral treatment as soon as possible.
3. Notify the state or local health department.
4. Using personal protective equipment, collect respiratory specimens from the patient to test for novel influenza A viruses at a public health laboratory (e.g., state health department virology laboratory).
5. Consider testing for other potential causes of acute respiratory illness based upon the local epidemiology of circulating respiratory viruses, including SARS-CoV-2.

If signs/symptoms and a history of exposures to animals or to a symptomatic confirmed or probable human case of novel influenza A virus infection compatible with novel influenza A virus infection are not present:

1. Follow standard health care facility infection control practices/protocols.
2. Investigate other potential causes of the patient's signs and symptoms.
3. Contact state/local health department with any questions or concerns.

Signs/symptoms of novel influenza A virus infection in humans may include:

• Uncomplicated upper respiratory tract signs and symptoms with or without fever, including influenza-like illness (ILI) [fever ≥100°F plus cough or sore throat]
• Fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish
• Cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue
• Eye redness (or conjunctivitis)
• Shortness of breath or difficulty breathing.
• Less common signs and symptoms are diarrhea, nausea, or vomiting.
• It is important to note that infection with influenza viruses, including novel influenza A viruses, does not always cause fever. Fever may not occur in infected persons of any age, particularly in persons aged 65 years and older or people with immunosuppression. The absence of fever should not supersede clinical judgment when evaluating a patient for illness compatible with novel influenza A virus infection.

Infection prevention and control recommendations: Standard, contact and airborne precautions, including the use of eye protection, are recommended when evaluating patients for infection with novel influenza A viruses. If an airborne infection isolation room (AIIR) is not available, isolate the patient in a private room. Health care personnel should wear recommended personal protective equipment (PPE) when providing patient care. For more information on recommended infection prevention and control measures, please visit Infection Control Within Healthcare Settings for Patients with Novel Influenza A Viruses.

Laboratory testing recommendations: If signs or symptoms consistent with infection with novel influenza A virus are present in a patient with recent exposure to infected birds or other animals, contaminated environments, or contaminated materials, or to a symptomatic person confirmed with novel influenza A virus infection, respiratory specimens should be collected for molecular testing (RT-PCR) for influenza A viruses, including novel influenza A viruses. For outpatients, upper respiratory tract specimens such as a nasopharyngeal swab and a nasal swab combined with an oropharyngeal swab (e.g., two swabs combined into one viral transport media vial) should be collected. The nasopharyngeal swab and the combined nasal-throat swabs should be tested separately. If the person has conjunctivitis (with or without respiratory symptoms), both a conjunctival swab and nasopharyngeal swab should be collected.

Patients who are severely ill should have both upper and lower respiratory tract specimens (e.g., an endotracheal aspirate or bronchoalveolar lavage fluid in intubated patients or induced sputum) collected for influenza testing. For information on specimen collection, infection prevention and control recommendations when collecting specimens, and influenza diagnostic testing, please visit Specimen Collection and Testing for Patients with Novel Influenza A Viruses with Potential to Cause Severe Disease in Humans.

Testing for novel influenza A viruses must be performed at public health laboratories (e.g., state health department virology laboratories) and CDC. Rapid influenza diagnostic tests are not a reliable indicator of novel influenza A virus infection, and the results should not be used to guide infection control or antiviral treatment decisions. Both commercially available rapid influenza diagnostic tests and most available influenza molecular assays do not distinguish between infection with seasonal influenza A viruses and novel influenza A viruses.

Testing for other potential causes of acute respiratory illness (e.g., SARS-CoV-2) should also be considered depending upon the local epidemiology of circulating respiratory viruses.

Treatment recommendations: Initiation of antiviral treatment with oral oseltamivir (twice daily x 5 days) is recommended as soon as possible for any patient with confirmed, probable, or suspected infection with a novel influenza A virus. Treatment should be initiated even if more than 48 hours have elapsed since illness onset and regardless of illness severity (outpatients or hospitalized patients).

Antiviral treatment should not be delayed while waiting for laboratory test results. If molecular testing is negative for novel influenza A virus infection and other influenza viruses, but influenza virus infection is still suspected in a patient who is severely ill, antiviral treatment should be continued and additional respiratory specimens should be collected for repeat influenza testing. For patients who are not hospitalized, if molecular testing is negative for novel influenza A virus and other influenza viruses, antiviral treatment can be discontinued.