The recommendations in this Health Alert are based on the current situation and knowledge. Recommendations are changing quickly and this Health Alert will be updated as necessary.
The Delaware Division of Public Health (DPH) is reporting 10 confirmed and 16 probable cases of swine-origin influenza A (H1N1) virus infection. The onset of the first case was April 24. In addition, more than 500 symptomatic University of Delaware Students were treated for antiviral agents at the University Health Center or a Division of Public Health clinic between April 29 and May 1.
Because swine influenza is confirmed in University of Delaware students, DPH is not recommending routine testing of University of Delaware students for clinical purposes. Symptomatic students should be treated empirically.
Clinical decisions may need to be made empirically or on the basis of influenza rapid antigen test. However, these tests have unknown sensitivity and specificity to detect human infection with swine-origin 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-origin influenza infection.
For the purposes of disease surveillance, DPH is recommending that persons other than University of Delaware students with influenza-like symptoms be tested if they present with a fever >100° F and cough or sore throat.
The DPH Laboratory will perform Real-time RT-PCR for influenza A, B, H1, H3. Currently, swine-origin 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, it is more suggestive of a novel influenza A virus, such as the Swine-origin influenza virus. Confirmation as swine-origin influenza A (H1N1) virus is performed at CDC currently, but may be available in state public health laboratories soon.
The swine-origin influenza virus is susceptible to both oseltamivir and zanamivir. It is resistant to amantadine and rimantadine. Interim guidance on antiviral treatment for swine-origin influenza A (H1N1) can be found at:
Antiviral treatment should be considered for confirmed, probable or suspected cases of swine-origin influenza A (H1N1) virus infection. Treatment of hospitalized patients and patients at higher risk for influenza complications should be prioritized.
Antiviral treatment with zanamivir or oseltamivir should be initiated as soon as possible after the onset of symptoms. Evidence for benefits from treatment in studies of seasonal influenza is strongest when treatment is started within 48 hours of illness onset. However, some studies of treatment of seasonal influenza have indicated benefit, including reductions in mortality or duration of hospitalization even for patients whose treatment was started more than 48 hours after illness onset. Recommended duration of treatment is five days. Recommendations for use of antivirals may change as data on antiviral susceptibilities and effectiveness become available. Antiviral doses recommended for treatment of swine-origin influenza A (H1N1) virus infection in adults or children 1 year of age or older are the same as those recommended for seasonal influenza. Oseltamivir use for children < 1 year old was recently approved by the U.S. Food and Drug Administration (FDA) under an Emergency Use Authorization (EUA), and dosing for these children is age-based.
Availability: DPH is aware that prescriptions for antiviral medications may be difficult to fill. Experience to date in Delaware and nationally suggests that the vast majority of illness is uncomplicated and recovery is complete without treatment. Both the availability of antiviral medications and our understanding of the ususal course of the illness are evolving.
Additional therapy such as antibacterial agents, should be used at the discretion of the clinicians given the patients clinical presentation. For antibacterial treatment of pneumonia, clinical guidance for community-acquired pneumonia should be followed and can be accessed at http://www.journals.uchicago.edu/doi/pdf/10.1086/511159?cookieSet=1.
For hospitalized patients with severe community-acquired pneumonia (CAP) requiring intensive care unit admission, menthicillin-resistent Staphylococcus aureus (MRSA) infection should be suspected and treated empirically in addition to other causes of CAP if they have 1) necrotizing or cavitary infiltrates or 2) empyema.
For antiviral chemoprophylaxis of swine-origin influenza A (H1N1) virus infection, either oseltamivir or zanamivir are recommended. Duration of antiviral chemoprophylaxis post-exposure is 10 days after the last known exposure to an ill confirmed case of swine-origin influenza A (H1N1) virus infection. Post exposure prophylaxis should be considered for contact during the infectious period (e.g., one day before until 7 days after the case’s onset of illness). If the contact occurred more than 7 days earlier, then prophylaxis is not necessary. Antiviral chemoprophylaxis with either oseltamivir or zanamivir is recommended for the following individuals:
Antiviral chemoprophylaxis with either oseltamivir or zanamivir can be considered for the following:
Close contact is defined as: within about 6 feet of an ill person who is a confirmed or suspected case of swine-origin influenza A (H1N1) virus infection during the case’s infectious period.