The information below is intended for Drexel University College of Medicine faculty physicians in their role as clinicians. It is not intended for patients and should not be used as a substitute for consultation with a physician or healthcare professional. If you have specific questions or concerns about your health, you should consult your healthcare provider.
Influenza A (H1N1) virus infection, commonly known as “swine flu”, has reappeared in Pennsylvania. At the moment, 98% of all influenza virus strains circulating are the A(H1N1) virus. It continues to present as a relatively mild illness in most infected persons, no more virulent that the standard “seasonal” influenza viruses. Genetic testing of the virus also reveals the absence of virulence factors that would be of concern.
Nevertheless, as in any influenza virus outbreak, the proper preventive and treatment measures need to be taken. Various H1N1 vaccines will be available from the U.S. government free of charge in early to mid-October. Those who should receive vaccine include children and young adults 6 months-24 years; parents and household contacts of children less than 6 months; pregnant women; healthcare workers, including medical students; and adults 25-64 with medical conditions predisposing them to high risk for complications of influenza (listed below).
Details regarding the distribution and administration of vaccine will be forthcoming. The possible vaccines include killed viral antigen vaccines given parenterally and an attenuated live virus “Flu Mist” vaccine administered intranasally. The latter vaccine is likely to be available first. The killed virus parenteral vaccines are preferable for children less than 24 months, pregnant women, immunocompromised persons, persons with respiratory conditions such as asthma, and persons with chronic medical conditions such as heart disease, kidney disease,and diabetes. The standard “seasonal” influenza vaccine is already available and can be given at the same time as the H1N1 influenza vaccine.
As a reminder, influenza usually presents as an acute respiratory illness consisting of the recent onset of the following: rhinorrhea or nasal congestion, sore throat, cough (with or without fever or feverishness). Many cases of H1N1 influenza have been presenting without fever.
The usual infectious period for swine flu infection is from 1 day before the onset of illness to 7 days after onset. Young infants and immunosuppressed persons may be contagious for longer periods.
Close contact is defined as being within about 6 feet of an infected person during the infectious period.
Testing for swine influenza. The sensitivity of the rapid influenza antigen test is only 40-70%. Negative samples can be processed for further testing.
A nasopharyngeal swab/aspirate or nasal wash/aspirate is preferred. A combined nasal swab with an oropharyngeal swab is an acceptable alternative. The swabs should have a synthetic tip (e.g., polyester or Dacron) and an aluminum or plastic shaft (not cotton tips and wooden shafts; not calcium alginate).
Specimens should be placed into sterile viral transport media and immediately placed on ice or cold packs for transport to the laboratory.
Treatment. At the moment, most strains of the swine influenza A circulating are sensitive to oseltamivir and zanamivir, and resistant to amantadine and rimantadine, but some oseltamivir/zanamivir-resistant strains have appeared. Early (within 48 hours of illness onset) treatment is more beneficial, but later treatment may be effective, too. The recommended duration of treatment is 5 days. You should consider treatment for all confirmed, probable, or suspected cases, but particularly for patients at higher risk for influenza complications.
It is important to remember that a significant portion of the morbidity and mortality related to influenza is from the complicating bacterial pneumonia that may occur, so patients should be closely monitored and treated for this development.
Prevention/Isolation [revised]. CDC recommends that people with influenza-like illness remain at home until at least 24 hours after they are free of fever (100° F [37.8°C]), or signs of a fever without the use of fever-reducing medications. This is a change from the previous recommendation that ill persons stay home for 7 days after illness onset or until 24 hours after the resolution of symptoms, whichever was longer. Persons seeking medical care should contact their health care providers by phone first before seeking care. Those with difficulty breathing or deemed to be ill enough should get immediate medical attention.
If ill persons go into the community or are within 6 feet of others at home, they should wear a face mask (if tolerable) or otherwise cover their coughs. Patients, healthcare workers and household members should wash their hands frequently.
Hospitalized patients: The recommended duration of isolation precautions for hospitalized patients is longer than that recommended for other populations because duration of virus shedding is likely to be longer than for outpatients with milder illness. Isolation precautions for patients who have influenza symptoms should be continued for the 7 days after illness onset or until 24 hours after the resolution of fever and respiratory symptoms, whichever is longer, while a patient is in a healthcare facility.
Healthcare personnel who develop a fever and respiratory symptoms should be
- Instructed not to report to work, or if at work, to promptly notify their supervisor and infection control personnel/occupational health.
- Excluded from work for at least 24 hours after they no longer have a fever, without the use of fever-reducing medicines.
- If returning to work in areas where severely immunocompromised patients are provided care, considered for temporary reassignment or exclusion from work for 7 days from symptom onset or until the resolution of symptoms, whichever is longer.
Healthcare personnel who develop acute respiratory symptoms without fever should be
- Allowed to continue or return to work unless assigned in areas where severely immunocompromised patients are provided care. In this case they should be considered for temporary reassignment or exclusion from work for 7 days from symptom onset or until the resolution of symptoms, whichever is longer.
Antiviral prophylaxis is recommended for the following:
- Household close contacts of a confirmed, probable, or suspected case and who are at high risk for complications of influenza.
- School children who had close contact and who are at high risk for complication of influenza.
- Healthcare workers or public health workers who were not using appropriate personal protective equipment during close contact with a confirmed, probable, or suspected case during the case’s infectious period.
Persons at high risk for complications of influenza:
- Age ≥65 years.
- Residents of nursing homes and other chronic-care facilities
- Persons with chronic pulmonary or cardiovascular diseases
- Persons with chronic metabolic diseases (including diabetes mellitus), renal dysfunction, hemoglobinopathies, or immunosuppression (including HIV)
- Children and adolescents receiving long-term aspirin therapy
- Women in the second or third trimester of pregnancy
- Children aged 6 months-23 months
Information and recommendations may change again as more is learned. The Division of Infectious Diseases and HIV Medicine is available to provide advice to you about your patients, and consultation, if needed (215-762-6555).
More information can be found at cdc.gov/H1N1flu.
Jeffrey M. Jacobson, M.D.
Professor of Medicine, Microbiology and Immunology
Chief, Division of Infectious Diseases and HIV Medicine
The information in this document is intended by Dr. Jacobson for his physician colleagues. It is not intended for patients and should not be used as a substitute for consultation with a physician or healthcare professional. If you have specific questions or concerns about your health, you should consult your healthcare provider.