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As of April 5, 2008.


Week and year


*The national and regional baselines are the mean percentage of visits for ILI during noninfluenza weeks for the previous three seasons plus two standard deviations. A noninfluenza week is a week during which <10% of speciments tested positive for influenza. National and regional percentages of patient visits for ILI are weighted on the basis of state population. Use of the national baseline for regional data is not appropriate.

$The national, regional, and age-specific baselines are the mean percentage of visits for ARI during noninfluenza weeks for the previous three seasons plus two standard deviations. A noninfluenza week is a week during which <10% of specimens tested positive for influenza. Use of national baseline for regional data is not appropriate.

FIGURE 3. Estimated influenza activity levels reported by state epidemiologists, by state and level of activity-United States, week ending April 5, 2008

No report
No activity

Regional Widespread

* Levels of activity are 1) no activity, 2) sporadic. isolated laboratory-confirmed influenza cases or a laboratory-confirmed outbreak in one institution, with no increase in activity; 3) local: increased ILI, or at least two institutional outbreaks (ILI or laboratory-confirmed influenza) in one region with recent laboratory evidence of influenza in that region (virus activity no greater than sporadic in other regions); 4) regional increased ILI activity or institutional outbreaks (ILI or laboratory-confirmed influenza) in at least two but less than half of the regions in the state with recent laboratory evidence of influenza in those regions; and 5) widespread. increased ILI activity or institutional outbreaks (ILI or laboratory-confirmed influenza) in at least half the regions in the state with recent laboratory evidence of influenza in the state.

Network (NVSN). During November 4, 2007-March 22 2008, the preliminary laboratory-confirmed influenzaassociated hospitalization rate reported by NVSN for chi dren aged 0-4 years was 5.61 per 10,000. During September 30, 2007-March 29, 2008, EIP sites reported a preliminary laboratory-confirmed influenza-associated hospitalization rate of 1.32 per 10,000 for children aged 0-17 years. For children aged 0-4 years, the rate was 3.4 per 10,000, and for children aged 5-17 years, the rate was 0.45 per 10,000. Differences in the rate estimates betweer the NVSN and the EIP systems likely result from the dif ferent case-finding methods and the different populations monitored.***

Pneumonia and Influenza-Related

Pneumonia and influenza (P&I) was listed as an underlying or contributing cause of death for 8.9% of all death reported through the 122 Cities Mortality Reporting System for the week ending April 5, 2008. This percentage was above the epidemic threshold of 6.9% for the week and marked the thirteenth consecutive week that the proportion of all deaths attributed to P&I was above the ep demic threshold (Figure 4). The proportion of deaths from P&I exceeded the epidemic threshold during week ending January 5 and peaked at 9.1% during the week ending March 15.

Influenza-Related Pediatric Mortality

During September 30, 2007-April 5, 2008, a total o 65 pediatric deaths among children aged <18 years assoc



NVSN conducts surveillance in Monroe County, New York; Hamilton Count Ohio; and Davidson County, Tennessee. NVSN provides population-base estimates of laboratory-confirmed influenza hospitalization rates in children aged <5 years admitted to NVSN hospitals with fever or respiratory symptons Children are prospectively enrolled, and respiratory samples are collected and tested by viral culture and reverse transcription-polymerase chain reaction (RT-PCR). EIP conducts surveillance in 60 counties associated with 13 metropolitan areas: San Francisco, California; Denver, Colorado; New Haver Connecticut; Atlanta, Georgia; Baltimore, Maryland; Minneapolis/St. Pa Minnesota; Albuquerque, New Mexico; Las Cruces, New Mexico; Alban New York; Rochester, New York; Portland, Oregon; and Nashville, Tennessee EIP conducts surveillance for laboratory-confirmed, influenza-related hospitalizations in persons aged <18 years. Hospital laboratory and admission databases and infection-control logs are reviewed to identify children with a positive influenza test (i.e., viral culture, direct fluorescent antibody assays RT-PCR, or a commercial rapid antigen test) from testing conducted as a par of their routine care.

The expected seasonal baseline proportion of P&I deaths reported by the 12 Cities Mortality Reporting System is projected using a robust regression procedure in which a periodic regression model is applied to the observed percentage of deaths from P&I that occurred during the preceding 5 years The epidemic threshold is 1.645 standard deviations above the seasona baseline.

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esistance to Antiviral Medications During this influenza season, an increase in the number influenza viruses resistant to the neuraminidase inhibi›r, oseltamivir, has been observed. Among the 1,153 fluenza A and B viruses tested during the 2007-08 fluenza season, to date, 84 (8.3%) have been found to be sistant to oseltamivir. All the oseltamivir-resistant viruses ave been influenza A (H1N1) viruses and have been etermined to share the same genetic mutation that conrs oseltamivir resistance. These 84 viruses represent 10.2% the 824 influenza A (H1N1) viruses that have been sted, an increase from four (0.7%) of 588 influenza A H1N1) viruses tested during the 2006-07 season. No sistance to oseltamivir has been identified among the 194 fluenza A (H3N2) or the 135 influenza B viruses tested, id no antiviral resistance to zanamivir has been detected any influenza A or B viruses. Resistance to adamantanes mantadine and rimantadine) continues to be high among fluenza A viruses. Of 261 influenza A (H3N2) viruses sted, 260 (99.6%) were resistant to adamantanes. damantane resistance among influenza A (H1N1) viruses

also has been detected, but at a lower level. Of 729 influenza A (H1N1) viruses tested, 81 (11.1%) were resistant to adamantanes. The adamantanes have no activity against influenza B viruses.

Based on the level of oseltamivir resistance observed in only one influenza A subtype (H1N1), persisting high levels of resistance to adamantanes in A (H3N2) viruses, and the predominance of A (H3N2) viruses circulating in the United States during the 2007-08 season with cocirculation of influenza B viruses, CDC continues to recommend the use of oseltamivir and zanamivir for the treatment or chemoprophylaxis of influenza (2). Use of amantadine or rimantadine is not recommended. Reported by: World Health Organization Collaborating Center for Surveillance, Epidemiology, and Control of Influenza; C Dao, MPH, L Blanton, MPH, S Epperson, MPH, L Brammer, MPH, L Finelli, DrPH, TWallis, MS, TUyeki, MD, J Bresee, MD, A Klimov, PhD, N Cox, PhD, Influenza Div, National Center for Immunization and Respiratory Diseases, CDC.

Editorial Note: By some indicators, this influenza season has been more severe than the previous three seasons. Influenza activity in the United States remained low until January, peaked in mid-February, and decreased thereafter. For the week ending April 5, 2008, widespread activity was reported in six states, and regional activity was reported in 11 states, a decrease from mid-February, when 49 states reported widespread activity and one state reported regional activity. During peak activity of the previous three influenza seasons, the number of states reporting widespread or regional activity ranged from 41 to 49 states. During the 2007-08 season, the percentage of outpatient visits for ILI peaked at 5.9%, exceeded the national baseline for 13 consecutive weeks, and declined to 1.7% during the week ending April 5. During the previous three influenza seasons, the peak percentage of visits for ILI ranged from 3.2% to 5.4% and exceeded baseline levels for 14 to 16 consecutive weeks. To date, the percentage of deaths attributable to P&I peaked at 9.1% and exceeded the epidemic threshold for 13 consecutive weeks this season. For the week ending April 5, the proportion of deaths attributable to P&I was 8.9%. During the previous three seasons, the peak percentage of deaths attributable to P&I ranged from 7.7% to 8.9%, and the total number of weeks above the epidemic threshold ranged from 1 to 11 consecutive weeks. P&I mortality is higher this season than the previous three seasons, which were mild. The 2007-08 season is similar to the 2003-04 season, when the percentage of deaths attributable to P&I peaked at 10.4% and the number of consecutive weeks above the epidemic threshold was 9 weeks.

Influenza A (H1N1) viruses predominated through midJanuary, but influenza A (H3N2) viruses were more frequently identified than influenza A (H1N1) viruses since late January and have predominated overall. The majority of influenza A (H1N1) viruses were characterized as A/Solomon Islands/3/2006, the influenza A (H1N1) component of the 2007-08 influenza vaccine for the Northern Hemisphere. To date, the majority of influenza A (H3N2) and influenza B viruses were characterized as A/Brisbane/ 10/2007 and B/Florida/04/2006, respectively, the recommended influenza A (H3N2) and influenza B components of the 2008-09 influenza vaccine for the Northern Hemisphere.

Clinical vaccine effectiveness cannot be accurately predicted using these data. A case-control study to estimate the effectiveness of trivalent inactivated influenza vaccine was conducted this season in Marshfield, Wisconsin. Preliminary results from subjects enrolled during January 21February 8 show an overall vaccine effectiveness of 44%, suggesting that vaccination provided substantial protection against influenza-associated, medically attended illness in the study population, despite the suboptimal vaccine match (3). These preliminary results are similar to previous studies, which have shown that influenza vaccination provides measurable protection against influenza illness and influenza-related complications and death, even when vaccine strains are antigenically distinct from circulating strains (4-7).

As a supplement to influenza vaccination, antiviral drugs have aided in the control and prevention of influenza. Recent studies have identified a considerable protective effect of oseltamivir treatment against complications associated with influenza (8), including death among older adults hospitalized with laboratory-confirmed influenza (9). This season, resistance to the influenza antiviral drug oseltamivir among influenza A (H1N1) viruses (84 [10.2%] of 824 tested) has been detected. All 84 resistant influenza A (H1N1) viruses identified in the United States this season share the same genetic mutation; this mutation is the most common mutation in this subtype that confers resistance to oseltamivir. Increased resistance to oseltamivir among influenza A (H1N1) viruses has been reported from many countries this season (10). No oseltamivir resistance has been detected among influenza A (H3N2) or B viruses currently circulating in the United States. Given the low level of resistance to oseltamivir, the finding of resistance only in some influenza A (H1N1) viruses, and no resistance to zanamivir, these drugs continue to be recommended for the treatment and prophylaxis of influenza (2). Although

recommendations for use of antiviral medications have n changed, enhanced surveillance for detection of oseltamivitresistant influenza viruses is ongoing and will enable cotinued monitoring of changing trends over time. In addition. to vaccination and antivirals, other means of decreasing the spread and impact of influenza include staying home frer. work or school when ill, avoiding others who are sick, cov ering the nose or mouth with a tissue when coughing of sneezing, and frequent hand washing. Additional informa tion is available at


Influenza surveillance reports for the United States are posted online weekly during October-May and are avail able at Additional information regarding influenza viruses, infenza surveillance, the influenza vaccine, and avian influenza is available at


This report is based on data contributed by participating state and territorial health departments and state public health laboratories, Worc Health Organization collaborating laboratories, National Respirato and Enteric Virus Surveillance System collaborating laboratories, tU.S. Influenza Sentinel Provider Surveillance System, the US Department of Veterans Affairs/U.S. Department of Defense BioSense Outpatient Surveillance System, the New Vaccine Surveillance Network, the Emerging Infections Program, and the 122 Cities Mortalit Reporting System.


1. CDC. Update: influenza activity-United States, September 31February 9, 2008. MMWR 2008;57:179–83.

2. CDC. Health Advisory: influenza antiviral use for persons at

high for influenza complications or who have severe influenza illness. Atlant GA: US Department of Health and Human Services, CDC; 200Available at alertnum=00271.

3. CDC. Interim within-season estimate of the effectiveness of triva.einactivated influenza vaccine-Marshfield, Wisconsin, 2007influenza season. MMWR 2008;57:393-8.

4. Edwards KM, Dupont WD, Westrich MK, Plummer WD Jr, Palme PS, Wright PF. A randomized controlled trial of cold-adapted ar inactivated vaccines for the prevention of influenza A disease. J Inte Dis 1994;169:68–76.

5. Nichol KL, Nordin JD, Nelson DB, Mullooly JP, Hak E. Effectivene of influenza vaccine in the community-dwelling elderly. N Engl J Me 2007;357:1373-81.

6. Shuler CM, Iwamoto M, Bridges CB. Vaccine effectiveness agair medically attended, laboratory-confirmed influenza among childre aged 6 to 59 months, 2003–2004. Pediatrics 2007;119:e587–95. 7. Russell KL, Ryan MA, Hawksworth A, et al. Effectiveness of th 2003-2004 influenza vaccine among U.S. military basic trainees. year of suboptimal match between vaccine and circulating strain. Va cine 2005;23:1981-5.

8. Kaiser L, Wat C, Mills T, Mahoney P, Ward P, Hayden F. Impact oseltamivir treatment on influenza-related lower respiratory tract cor plications and hospitalizations. Arch Intern Med 2003;163:166~~~:

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The week of April 19-26, 2008, is National Infant nmunization Week (NIIW) and Vaccination Week in the mericas (VWA). Immunization is one of the most effecve ways to protect infants and children from potentially erious diseases. During the week, hundreds of communies throughout the United States are expected to sponsor ctivities to emphasize the health benefits of timely vacciation and the importance to parents, health-care providrs, and communities of maintaining high vaccination ɔverage. One message stressed during this week will be he key role of the ongoing relationship among parents and heir children's health-care providers in vaccination prorams. CDC encourages parents to talk to their healthare providers about vaccinations at any time.

The week's activities provide an opportunity to showcase he success of vaccination in saving the lives and protecting he health of children. The currently recommended childood vaccination schedule (1) includes vaccines that preent infectious diseases such as measles, polio, whooping ɔugh, some forms of meningitis and pneumonia, and liver incer. An analysis of the impact of seven vaccines showed hat they would prevent approximately 33,500 deaths and 4 million illnesses per annual birth cohort (2). NIIW-VWA events held in collaboration with CDC and ate and local health departments will be hosted in Rhode land, Connecticut, and Washington. Events held in colboration with CDC, state and local health departments, he United States-Mexico Border Health Commission, and ne Pan American Health Organization (PAHO), will be ɔsted in communities along the U.S.-Mexico border, with ick-off events held in El Paso, Texas, and Sunland Park, [ew Mexico. In all locations, events will include educaon activities for health-care providers, media briefings, nd immunization clinics.

VWA, sponsored by PAHO, targets children and other lnerable and underserved populations who have low vacnation coverage rates, in all countries in the Western hemihere. To support NIIW and VWA events nationwide,

CDC provides annually updated English- and Spanishlanguage planning guides, campaign materials, and public relations tools. These include timely key messages, radio public service announcements, and sample media kits. These resources and event listings are available at http:// Additional information about VWA is available at http://www.paho. org/english/dd/pin/vw2008.htm.


1. CDC. Recommended immunization schedules for persons aged 0-18 years—United States, 2008. MMWR 2008;57:Q1–4.

2. Zhou F, Santoli J, Messonnier ML, et al. Economic evaluation of the 7vaccine routine childhood immunization schedule in the United States, 2001. Arch Pediatr Adolesc Med 2005;159:1136–44.

Notice to Readers

International Course in Applied

CDC and Emory University's Rollins School of Public Health will cosponsor the International Course in Applied Epidemiology, to be held September 22-October 17, 2008, in Atlanta, Georgia. The course is designed for public health professionals from countries other than the United States. It will include presentations and discussions of epidemiologic principles, basic statistical analysis, public health surveillance, field investigations, surveys and sampling, and the epidemiologic aspects of current major public health problems in global health.

Group discussions of epidemiologic case exercises based on field investigations will be held during the course. Participants are encouraged to give a short presentation reviewing some epidemiologic data from their own country. The course also will include computer training using Epi Info (Windows version), a software program for epidemiologists developed at CDC and the World Health Organization.

Prerequisites are familiarity with the vocabulary and principles of basic epidemiology, or completion of CDC's Principles of Epidemiology home-study course or equivalent. Preference will be given to applicants whose work involves priority public health problems in international health. Tuition is charged.

Additional information and applications are available by mail (Emory University, Rollins School of Public Health, Hubert Global Health Dept. [Attn: Pia], 1518 Clifton Rd. NE, Rm. 746, Atlanta, GA 30322); fax (404-727-4590), e-mail (, or Internet (http://www.

Notice to Readers

Web Series: HIV/AIDS Crisis Among

African Americans

CDC and the Public Health Training Network will offer the six-part web series, A Call to Action for Leaders: The Crisis of HIV/AIDS Among African Americans, available online beginning June 30, 2008. This series is designed to 1) increase awareness of HIV/AIDS in African American communities; 2) highlight innovative, sustainable, and collaborative actions taken by leaders in places where African Americans live, work, play, learn, and worship; and 3)

provide links to available resources. David Satcher, form: Director of CDC and the 16th Surgeon General of the United States, will serve as senior host of the web series.

Each part of the series is a prerecorded, 30-minute segment, which can be viewed on computers with Internet access and Windows Media Player. The series will be avai able at Parts 1-3 can be vieweć beginning June 30, and parts 4-6 can be viewed begin ning November 30. A free DVD of this series can ordered by telephone (800-458-5231) after June 30 (pars 1-3) and after November 30 (parts 1-6).

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