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PREVENTION AND CONTROL OF INFLUENZA Lisa McHugh, MPH Influenza can be a serious illness for people of any age. Every year, more than 200,000 people across the United States are hospitalized and at least 36,000 people die as a result of the flu [1, 2]. From 1999-2003, 70 influenza-associated deaths occurred in New Jersey residents [3]. In the United States, annual epidemics of influenza typically occur during the fall or winter months, but the peak of influenza activity can occur as late as April or May (Figure 1). Rates of infection are highest among children, but rates of serious illness and death are highest among persons age >65 years, children <2 years, and persons of any age who have medical conditions that place them at increased risk for complications from influenza. Health care providers can reduce illness and death from influenza and pneumonia by getting immunized themselves, by providing flu vaccine to their patients, and by giving pneumococcal vaccine to those at risk, especially those 65 years and older. CLINICAL SIGNS AND SYMPTOMS OF INFLUENZA Influenza viruses are spread from person to person primarily through largeparticle respiratory droplet transmission. Transmission via large-particle droplets requires close contact between source and recipient persons because droplets do not remain suspended in the air and generally travel As soon as influenza vaccine becomes available immunize! Immunize patients when they come in for any office visit. All health care workers should receive an annual flu vaccine. only a short distance (<1 meter) through the air. Contact with respiratory-droplet contaminated surfaces is another possible source of transmission. The typical incubation period for influenza is 1-4 days (average: 2 days). Adults can be infectious from the day before symptoms begin through approximately 5 days after illness onset. Young children also might shed virus several days before illness onset, and children can be infectious for >10 days after symptom onset. Severely immunocompromised persons can shed virus for weeks or months. Uncomplicated influenza illness is characterized by the abrupt onset of constitutional and respiratory signs and symptoms (e.g., fever, myalgia, headache, malaise, nonproductive cough, sore throat, and rhinitis). Among children, otitis media, nausea, and vomiting also are commonly reported with influenza illness. Uncomplicated influenza illness typically resolves after 3-7 days for the majority of persons, although cough and mal- Percent of Activity 50 40 30 20 10 0 3 13 19 aise can persist for >2 weeks. Influenza virus infections can cause primary influenza viral pneumonia; exacerbate underlying medical conditions (e.g., pulmonary or cardiac disease); lead to secondary bacterial pneumonia, sinusitis, or otitis; or contribute to coinfections with other viral or bacterial pathogens. HOSPITALIZATIONS AND DEATHS FROM INFLUENZA Influenza-related hospitalizations or deaths can result from the direct effects of influenza virus infection or from complications due to underlying cardiopulmonary conditions and other chronic diseases. Rates of influenzaassociated hospitalization are higher FIGURE 1 45 Nov Dec Jan Feb Mar Apr May Month Month of Peak Influenza Activity, United States, 1976-2006 13 3 3

among young children than among older children when influenza viruses are in circulation and are similar to rates for other groups considered at high risk for influenza-related complications, including persons aged >65 years. Hospitalization rates during influenza season are substantially increased for persons aged >65 years. Influenza-associated deaths are uncommon among children but represent a substantial proportion of vaccine-preventable deaths. Surveillance conducted in the 2005-2006 influenza season by the New Jersey Department of Health and Senior Services (NJDHSS) identified 25 cases of severe or fatal pediatric influenza in New Jersey. (http://nj.gov/health/flu/ professionals.shtml) VACCINE COMPOSITION Both live attenuated (i.e., procedure which makes the strain of the virus less virulent) influenza vaccine (LAIV) and inactivated vaccine (TIV) contain strains of influenza viruses that are antigenically equivalent to the annually recommended strains: one influenza A (H3N2) virus, one influenza A (H1N1) virus, and one influenza B virus. Each year, one or more virus strains might be changed on the basis of global surveillance for influenza viruses and the emergence and spread of new strains. Only the H1N1 strain was changed for the recommended vaccine for the 2007 08 influenza season, compared with the 2006 07 season. Viruses for both types of currently licensed vaccines are grown in eggs. Both vaccines are TABLE 1 Who Should Receive an Annual Influenza Vaccination? Anyone (including school-aged children) who wants influenza vaccine to reduce their risk of getting sick with the flu or giving it to others. People at high risk for complications from the flu, including: Children aged 6 months until their 5th birthday Pregnant women at any stage of pregnancy People 50 years of age and older People of any age with certain chronic medical conditions (Table 2) People > 6 months of age who live in nursing homes, chronic care facilities or other long term care facilities People who live with or care for those at high risk for complications from flu, including: administered annually to provide optimal protection against influenza virus infection. Both TIV and LAIV are widely available in the United States. Although both types of vaccines are expected to be effective, the vaccines. differ in several aspects. MAJOR DIFFERENCES BETWEEN TIV AND LAIV During the preparation of TIV, the vaccine viruses are made noninfectious (i.e., inactivated or killed). TIV contains killed viruses and thus cannot cause influenza. LAIV contains live, attenuated viruses and therefore has the potential to produce mild signs or symptoms related to attenuated influenza virus infection. LAIV is administered intranasally by sprayer, whereas TIV is administered intramuscularly by injection. LAIV is currently approved only for use among healthy persons aged 2 49 years; TIV is approved for use among persons Household contacts of persons at high risk for complications from the flu (see above) Household contacts and out-of-home caregivers of children less than 6 months of age (these children are too young to be vaccinated) Healthcare workers TABLE 2 Chronic Medical Conditions That Are Indications for Annual Flu Vaccination Cardiovascular disease Pulmonary disorders, including emphysema and asthma Chronic metabolic diseases, including all types of diabetes Renal disease (renal failure or renal dysfunction) Hemoglobinopathies (e.g., sickle cell disease, thalassemia) Immune dysfunction, including immunodeficiency caused by HIV infection or immunosuppressive therapy (e.g., radiation therapy, chemotherapy, high-dose steroids, or immunomodulating medications) Any condition that can compromise respiratory function, the handling of respiratory secretions, or that increases the risk of aspiration (e.g., cognitive dysfunction, spinal cord injuries, seizure disorder, or other neuromuscular disorders) Medical conditions treated with long-term aspirin therapy in children 6 months through 18 years, because of the potential risk of influenza-associated Reye syndrome. aged >6 months, including those who are healthy and those with chronic medical conditions. CONTRAINDICATIONS AND PRECAUTIONS TO VACCINE Influenza vaccines, both TIV and LAIV, should not be administered to any person who has had an anaphylactic reaction to eggs or to other components of the specific vaccine. However, allergic reactions are rare. Soreness or local irritation at the injection sites are reported by 15% to 20% of flu vaccine recipients. Fever and malaise are uncommon and are usually seen in individuals with no prior exposure to the influenza virus antigens in the vaccine, especially young children. OPTIONS FOR CONTROLLING INFLUENZA The most effective strategy for reducing the effect of influenza is annual vaccination. Antiviral drugs used for chemoprophylaxis or treatment of influenza are adjuncts to vaccine but are not substitutes for annual vaccination. Nonpharmacologic interventions (e.g., advising frequent handwashing and improved respiratory hygiene) are reasonable and inexpensive; these strategies have been demonstrated to reduce respiratory diseases but have not been studied adequately to determine if they specifically reduce transmission of influenza virus. There are four licensed agents effective against influenza: amantadine, rimantadine, zanamivir, and oseltamivir. Oseltamivir is approved for

TABLE 3 Surveillance Systems Description CDC Influenza Sentinel Provider Surveillance Network Health care providers from various disciplines and geographic locations weekly report the number of patient visits and the number of patients associated with influenza-like illness (ILI) by age category (e.g., 0-4 years; 5-24 years; 25-64 years; and > 65 years). Pediatric Influenza Surveillance Severe and fatal cases of influenza are collected from persons < 18 years of age. Influenza-like Illness (ILI) Surveillance Percent ILI is collected from hospital emergency departments and long term care facilities and percent absent is collected from schools each week. Select hospital laboratories also provide weekly reports on the number of respiratory syncytial virus tests performed and the number that are positive. Virologic Surveillance The New Jersey Public Health and Environmental Laboratories (PHEL) routinely test (PCR and viral culture)samples submitted by hospitals and private providers for influenza. Data regarding select respiratory and enteric viruses are also received from the National Respiratory and Enteric Virus Surveillance System (NREVSS). Other Respiratory Illness 122 City Mortality Report and other respiratory surveillance systems are also monitored for aberrations. treatment of persons aged 1 year and older and is licensed for use as chemoprophylaxis in persons aged 1 year and older. Zanamivir is approved for treatment of persons aged 7 years and older and is licensed for use as chemoprophylaxis in persons aged 5 years and older. CDC recommends that neither amantadine nor rimantadine be used for the trezatment or chemoprophylaxis of influenza in the United States during the 2007-08 influenza season because a high proportion of circulating influenza viruses have been found to be resistant to the adamantanes. (http:// www.cdc.gov/flu/professionals/ antivirals) HOW IS INFLUENZA MONITORED IN THE STATE AND WHERE CAN I GET INFORMATION? The NJDHSS Communicable Disease Service (CDS), along with many partners, actively monitors influenza activity. A variety of surveillance mechanisms are utilized to accurately assess influenza activity (Table 3). Throughout the flu season, regular updates on the level of flu activity are provided to health care providers, hospitals, and nursing homes via the NJ Health Alert Network (LINCS). Weekly reports are also posted weekly to the NJDHSS webpage. (http:// nj.gov/health/flu/surveillance.shtml) LABORATORY TESTING OF INFLUENZA Appropriate treatment of patients with respiratory illness depends on accurate and timely diagnosis. Early diagnosis of influenza can reduce the inappropriate use of antibiotics and provide the option of using antiviral therapy. However, because certain bacterial infections can produce symptoms similar to influenza, bacterial infections should be considered and appropriately treated, if suspected. In addition, bacterial infections can occur as a complication of influenza. Diagnostic tests available for influenza include viral culture, serology, rapid antigen testing, polymerase chain reaction (PCR), and immunofluorescence assays. Sensitivity and specificity of any test for influenza might vary by the laboratory that performs the test, the type of test used, and the type of specimen tested. Among respiratory specimens for viral Become part of an active surveillance system for ILI. In less than 30 minutes a week, you can participate as a sentinel provider in an important national public health initiative. The data you provide will help us monitor the impact of influenza in NJ. isolation or rapid detection, nasopharyngeal specimens are typically more effective than throat swab specimens. As with any diagnostic test, results should be evaluated in the context of other clinical and epidemiologic information available to healthcare providers. Commercial rapid diagnostic tests are available that can detect influenza viruses within 30 minutes. Some tests are approved for use in any outpatient setting, whereas others must be used in a moderately complex clinical laboratory. These rapid tests differ in the types of influenza viruses they can detect and whether they can distinguish between influenza types. Different tests can detect 1) only influenza A viruses; 2) both influenza A and B viruses, but not distinguish between the two types; or 3) both influenza A and B and distinguish between the two. None of the tests provide any information about influenza A subtypes. The types of specimens acceptable for use (e.g., throat, nasopharyngeal, or nasal aspirates, swabs, or washes) also vary by test. The specificity and, in particular, the sensitivity of rapid tests are lower than for viral culture and Contact the Influenza Surveillance Program at 609-588-7500.

BE A ROLE MODEL: Ensure that you and your family members get the flu vaccine and tell your colleagues and patients that you have done so. Emphasize that getting a flu vaccine is a priority for you as a health care provider, your colleagues and your staff. vary by test. Because of the lower sensitivity of the the rapid tests, physicians should consider confirming negative tests with viral culture or other means because of the possibility of false-negative rapid test results, especially during periods of peak community influenza activity. In contrast, false-positive rapid test results are less likely but can occur during periods of low influenza activity. Therefore, when interpreting results of a rapid influenza test, physicians should consider the positive and negative predictive values of the test in the context of the level of influenza activity in their community. Package inserts and the laboratory performing the test should be consulted for more details regarding use of rapid diagnostic tests. influenza A subtypes that might pose a pandemic threat. THE HEALTH CARE PROFESSIONALS ROLE IN PREVENTING INFLUENZA Patients are more likely to get an annual flu shot if their doctor recommends it. Recommending flu vaccine is as important as recommending any other life-saving measure. Every health care worker, paid and unpaid staff, volunteer, and home care attendant in all health care settings (hospitals, outpatient facilities, emergency departments, emergency medical services, clinics, offices, longterm care facilities, and assisted living settings) should receive a flu vaccine every year. Vaccination of health care workers not only protects workers but also protects colleagues, patients, families, and other close contacts. Health care providers and staff should receive flu vaccine early in the season to prevent the spread of illness to high -risk patients. FOR ADDITIONAL INFORMATION: http://nj.gov/health/flu/index.shtml http://www.cdc.gov/flu/ Despite the availability of rapid diagnostic tests, collecting clinical specimens for viral culture is critical, because only culture isolates can provide specific information regarding circulating strains and subtypes of influenza viruses. This information is needed to compare current circulating influenza strains with vaccine strains, to guide decisions regarding influenza treatment and chemoprophylaxis, and to formulate vaccine for the coming year. Virus isolates also are needed to monitor the emergence of antiviral resistance and the emergence of novel REFERENCES 1. Thompson WW, Shay DK, Weintraub E, et al. Mortality associated with influenza and respiratory synctial virus in the United States. JAMA 2003; 289:179-86. 2. Centers for Disease Control and Prevention, Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR. 2007;56(RR-6):1-60. 3. New Jersey Department of Health and Senior Services, NJSHAD Query System, http://njshad.doh.state.nj.us/dicd10.html