August 3, 2012
From: Lisa B. Hernandez, MD, MPH Kristy Michie, MS
Interim Health Officer 831-755-4585 Supervising Epidemiologist 831-755-4503
To date, no cases of H3N2v have been detected in California.
Since August 2011, a number of U.S. residents were found to be infected with a new variant of influenza virus, H3N2v, which includes a swine component. Investigations revealed human infections with these viruses followed contact with swine, as well as some limited human-to-human transmission. Cases have been reported in Hawaii, Indiana, Iowa, Maine, Ohio, Pennsylvania, Utah, and West Virginia. Sixteen of these cases occurred within the last three weeks.
The Monterey County Health Department received reports of influenza activity in July. However, polymerase chain reaction (PCR) analysis determined local activity was primarily due to the seasonal H3N2 strain of influenza A.
There is no indication that either the H3N2 or H3N2v strains are resistant to neuraminidase inhibitors.
At this time, the Health Department currently recommends all healthcare providers:
- Consider the possibility of influenza virus infection for individuals presenting with fever and 1) cough or 2) sore throat, irrespective of vaccination status.
- Ask suspected influenza cases about possible exposure to swine.
- Follow the standard seasonal influenza testing, treatment, and prophylaxis guidelines when managing suspected influenza cases (summary below). Remember that a negative rapid influenza test does not definitively rule out influenza virus infection.
- Promptly report cases of 1) severe influenza (fatal and/or admitted to the ICU) and 2) all laboratory confirmed cases of influenza who report swine exposure to the Health Department’s Communicable Disease Unit (phone: 831-755-4521; fax: 831-754-6682).
For additional information about influenza, please contact the Communicable Disease Unit at 831‑755‑4521. For information about influenza testing at the Monterey County Public Health Lab, call 831‑755‑4516.
Use your clinical judgment to guide testing decisions. Atypical presentations of influenza may occur (e.g., acute respiratory illness without fever), especially among young children, the elderly, and immunocompromised individuals. Results of any diagnostic test should be evaluated in the context of clinical and epidemiological information.
Reverse transcriptase polymerase chain reaction (RT-PCR) is the most sensitive test for detecting influenza viruses. It has the added ability to subtype influenza A. RT-PCR is available through the Monterey County Public Health Laboratory, Quest Diagnostics, and Laboratory Corporation of America.
Rapid diagnostic (antigen) tests have the advantage of being readily available at most facilities. However, while specificities are high during times of known influenza activity, the sensitivity of currently available rapid tests is generally low to moderate (range 10% to 80%). As a result, negative rapid test results do not exclude influenza virus infection and should not be used to make treatment or infection control decisions.
Acceptable specimens vary by the type of test. Specimens should be collected as close to illness onset as possible (ideally within 5 days). Nasopharyngeal and nasal specimens generally have higher yield for detection of influenza viruses than throat swab specimens.
Recommended antiviral medications are oseltamivir and zanamivir. Antiviral treatment is recommended as soon as possible for:
1) Patients with confirmed or suspected influenza who are hospitalized or have severe, complicated, or progressive disease; and
2) Outpatients with confirmed or suspected influenza who are at high risk for influenza complications based on their age and/or medical conditions. Individuals who are at high risk for complications include:
- Children <5 years of age, especially those <2 years of age
- Adults ≥65 years of age
- Individuals with chronic pulmonary, cardiovascular, renal, hepatic, hematological, and neurological conditions, as well as those with metabolic disorders including diabetes
- Immunocompromised individuals
- Pregnant or postpartum women
- Individuals <19 years who are on long-term aspirin therapy
- American Indians/Alaskan Natives
- Individuals who are morbidly obese (BMI ≥40)
- Residents of nursing homes and other chronic-care facilities
Treatment should not be delayed while waiting for laboratory test results. Treatment regimens may need to be altered to fit the clinical circumstances.
Antiviral treatment may be considered for any previously healthy, non-high risk symptomatic outpatient with confirmed or suspected influenza who is not in the recommended groups, based on clinical judgment, if treatment can be initiated within 48 hours of illness onset. Visit the Centers for Disease Control and Prevention’s website for complete antiviral treatment recommendations: (http://www.cdc.gov/flu/professionals/antivirals/summary-clinicians.htm).
Chemoprophylaxis with antiviral medications is not a substitute for influenza vaccination when vaccine is available. Please encourage your patients and staff to get immunized annually.
The likelihood of compliance and adverse events should be considered when determining the timing and duration for administering influenza antiviral medications for chemoprophylaxis. Decisions regarding whether to administer antivirals for chemoprophylaxsis should take into account:
- The exposed person’s risk for influenza complications,
- The type and duration of the exposure, and
- The length of time from the last exposure (in general, antivirals should only be started within 48 hours of the last exposure).
Healthcare providers should use clinical judgment regarding situations where early recognition of illness and treatment might be an appropriate alternative when managing some individuals who have had a suspected exposure to influenza.
Outpatient cases of seasonal influenza are not reportable, except when a novel strain is suspected. The following cases of influenza should be reported to the Health Department using the standard Confidential Morbidity Report (CMR) form:
- Fatal cases or cases requiring ICU admission, confirmed or suspected, any strain of influenza
- Outpatient cases of a novel strain of influenza (e.g., avian influenza) - Note: Pandemic 2009 H1N1 influenza is no longer considered a novel strain; however, H3N2v is considered a novel strain and is reportable.
- Suspected outbreaks of influenza at congregate living facilities, schools, daycares, and camps.
CMRs should be faxed to the Health Department (831-754-6682) within seven days of case identification. If you have additional questions or concerns, please call the Monterey County Health Department’s Communicable Disease Unit at 831-755-4521. To obtain a blank copy of the CMR form, visit the Communicable Disease Unit’s website: www.mtyhd.org/cdu.
Health Alert: Warrants immediate action or attention. Health Advisory: Provides information for a specific incident or situation; may not require immediate action. Health Update: Provides updated information regarding an incident or situation; unlikely to require immediate action.