Health Alert
DPH GUIDANCE FOR THE MEDICAL COMMUNITY IN DELAWARE REGARDING DIAGNOSIS AND TREATMENT OF SWINE INFLUENZA:
May 2, 2009 3:00 PM

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.

Situation

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.

Testing

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.

• Preferred respiratory specimens:  The following should be collected as soon as possible after illness onset: nasopharyngeal swab/aspirate or nasal wash/aspirate. If these specimens cannot be collected, a combined nasal swab with an oropharyngeal swab is acceptable. For patients who are intubated, an endotracheal aspirate should also be collected. Specimens should be placed into sterile viral transport media (VTM) and immediately placed on ice or cold packs or at 4°C (refrigerator) for transport to the laboratory.
• Swabs:  Ideally, swab specimens should be collected using swabs with a synthetic tip (e.g. polyester or Dacron®) and an aluminum or plastic shaft. Swabs with cotton tips and wooden shafts are not recommended. Specimens collected with swabs made of calcium alginate are not acceptable. The swab specimen collection vials should contain 1-3ml of viral transport medium (e.g. containing, protein stabilizer, antibiotics to discourage bacterial and fungal growth, and buffer solution), such M4RT or the BD Universal Viral Transport System.
• Storing Clinical Specimens:  All respiratory specimens should be kept at 4°C until they can be placed at -70°C.  If a -70°C freezer is not available, specimens should be kept at 4°C, preferably no longer than 1 week.
• Transport to DPH Laboratory:  DPH is finalizing arrangements in which clinicians will be able to drop off specimens to the DPH Laboratory at locations throughout the state. These arrangements should be announced on Monday, May 4. In the interim, clinicians should store clinical specimens as identified above.

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.

Treatment

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.

Chemoprophylaxis of contacts

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:

1. Household, intimate partners, or other close contacts who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, children younger than 5 years old, and pregnant women) of a confirmed or probable case (see below for definition of “close contact” and “high-risk for complications”).
2. Health care workers or public health workers who were not using appropriate personal protective equipment during close contact with an ill confirmed, probable, or suspect case of swine-origin influenza A (H1N1) virus infection during the case’s infectious period. See guidelines on personal protective equipment .

Antiviral chemoprophylaxis with either oseltamivir or zanamivir can be considered for the following:

1. Household close contacts who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 years or older, children younger than 5 years old, and pregnant women) of a suspected case.
2. Children attending school or daycare who are at high-risk for complications of influenza (children with certain chronic medical conditions) and who had close contact (face-to-face) with a confirmed, probable, or suspected case.
3. Health care workers who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, and pregnant women) who are working in an area of the healthcare facility that contains patients with confirmed swine-origin influenza A (H1N1) cases, or who is caring for patients with any acute febrile respiratory illness.
4. Travelers to Mexico who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, children younger than 5 years old, and pregnant women). (Note: A travel warning is currently in effect indicating that nonessential travel to Mexico should be avoided.
5. First responders who are at high-risk for complications of influenza (e.g., persons with certain chronic medical conditions, persons 65 or older, children younger than 5 years old, and pregnant women) and who are working in areas with confirmed cases of swine-origin influenza A (H1N1) virus infection.

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.

Persons at High-Risk for Medical Complications

• all children aged 6 months--4 years (59 months);
• all persons aged >50 years;
• children and adolescents (aged 6 months--18 years) who are receiving long-term aspirin therapy and who might be at risk for experiencing Reye syndrome after influenza virus infection;
• women who will be pregnant during the influenza season;
• adults and children who have chronic pulmonary (including asthma), cardiovascular (except hypertension), renal, hepatic, hematological, or metabolic disorders (including diabetes mellitus);
• adults and children who have immunosuppression (including immunosuppression caused by medications or by HIV);
• adults and children who have any condition (e.g., cognitive dysfunction, spinal cord injuries, seizure disorders, or other neuromuscular disorders) that can compromise respiratory function or the handling of respiratory secretions or that can increase the risk for aspiration; and
• residents of nursing homes and other chronic-care facilities.

More information:

http://www.cdc.gov/h1n1flu/guidance/