Summary Key Points

Summary Key Points

CDC Influenza Division Key PointsApril 12, 2013In this document: Summary Key Points FluView Activity Update Influenza-Related Pediatric Death CDC Antiviral Treatment Recommendations Message to Health Care Providers: Ordering Flu Vaccine for 2013-2014 Human Infections of Avian Influenza A (H7N9) Virus in ChinaSummary Key PointsInfluenza activity is continues to decline in the United States. (See Flu ActivityUpdate.)However, influenza may continue to spread at low levels and cause illness for severalweeks in some parts of the country. Five additional pediatric deaths were reported this week, bringing the total to 116pediatric deaths for the 2012-2013 influenza season. (See Influenza-RelatedPediatric Death section.)CDC routinely recommends vaccination as long as influenza viruses are circulating,but since it takes two weeks for vaccine to become protective and flu activity iswinding down, the window for vaccination this season is closing.However, ongoing vaccination is still recommended in institutional outbreak settings,for children needing to complete the second dose in their two-dose regime, and forpeople preparing to travel to the Southern Hemisphere, which is beginning to enterits traditional flu season.Because of the ongoing influenza activity, CDC continues to urge people at high riskfrom flu complications, including people 65 and older, to seek treatment quickly ifthey develop flu symptoms including cough, fever, sore throat, and body aches.Antiviral treatment can avert serious outcomes and should begin as quickly aspossible in high risk persons, including people 65 and older, young children,pregnant women, and people with certain underlying conditions like asthma, heartdisease, diabetes and neurological disorders. (See section on CDC’s AntiviralTreatment Recommendations.)The 2013-2014 influenza vaccine can be ordered at this time from manufacturersand distributors. (See section Message to Health Care Providers: Ordering FluVaccine for 2013-2014.)The World Health Organization (WHO) has reported several human infections withavian influenza A (H7N9) viruses in China. These infections have resulted in severeillness and, in some cases, death. (See section Human Infections of Avian InfluenzaA (H7N9) in China below.)On Friday, April 12, 2013, CDC posted a Flu Spotlight related to H7N9 cases inChina: “Additional H7N9 Cases Reported in China; CDC Receives H7N9 Virus Isolate.”1

CDC Influenza Division Key PointsApril 12, 2013The spotlight is available at Activity UpdateAccording to the latest FluView report, seasonal influenza activity is low and decliningnationally, though flu viruses continue to circulate and cause illness in the UnitedStates. Below is a summary of the key indicators for the week ending April 6, 2013.No jurisdictions reported high or moderate ILI activity for the week ending April 6. All50 states and New York City reported low or minimal ILI activity. Data from theDistrict of Columbia were insufficient to determine an ILI activity level. ILI activitydata indicate the amount of flu-like illness that is occurring in each jurisdiction.Four states reported widespread geographic influenza activity for the week endingApril 6. Seven states reported regional influenza activity. Geographic spread datashow how many areas within a state or territory are seeing flu activity.Since October 1, 2012, 12,052 laboratory-confirmed influenza-associatedhospitalizations have been reported; an increase of 254 hospitalizations from theprevious week. This translates to a cumulative rate of 43.2 influenza-associatedhospitalizations per 100,000 people in the United States for the 2012-2013 season.oHospitalization data are collected from 15 states and represent approximately9% of the total U.S. population. The number of hospitalizations reported doesnot reflect the actual total number of influenza-associated hospitalizations inthe United States.The proportion of deaths attributed to pneumonia and influenza (P&I) based on the122 Cities Mortality Reporting System decreased again this week and remains belowthe epidemic threshold. Five influenza-related pediatric deaths were reported during the week ending April 6,2013. One of the deaths was associated with an influenza A (H3) virus and four ofthe deaths were associated with influenza B viruses. This brings the total number ofinfluenza-associated pediatric deaths reported to CDC for 2012-2013 to 116.Additional information regarding pediatric deaths is available through FluViewInteractive.Nationally, the percentage of respiratory specimens testing positive for influenza inthe United States during the week ending April 6 decreased for the fourteenthconsecutive week. Influenza B viruses accounted for 71% of all reported influenzapositive specimens this week.Influenza A (H3N2), 2009 influenza A (H1N1), and influenza B viruses have all beenidentified in the U.S. this season. During the week ending April 6, 140 of the 484influenza-positive tests reported to CDC were influenza A viruses and 344 wereinfluenza B viruses. Of the 52 influenza A viruses that were subtyped, 75% were H3viruses and 25% were 2009 H1N1 viruses.2

CDC Influenza Division Key PointsApril 12, 2013Since October 1, 2012, CDC has antigenically characterized 2,098 influenza viruses,including 209 2009 influenza A (H1N1) viruses, 1,200 influenza A (H3N2) viruses and689 influenza B viruses.oooOf the 209 2009 influenza A (H1N1) characterized, 206 (98.6%) werecharacterized as A/California/7/2009-like. This is the influenza A (H1N1)component of the Northern Hemisphere vaccine for the 2012-2013 season.Of the 1,200 influenza A (H3N2) viruses, 1,196 (99.7%) were characterizedas A/Victoria/361/2011-like. This is the influenza A (H3N2) component of theNorthern Hemisphere influenza vaccine for the 2012-2013 season.Of the 689 influenza B viruses characterized, 68.8% belonged to theB/Yamagata lineage of viruses, and were characterized asB/Wisconsin/1/2010-like, the influenza B component for the 2012-2013Northern Hemisphere influenza vaccine. The remaining 31.2% of the testedinfluenza B viruses belonged to the B/Victoria lineage of viruses.Since October 1, 2012, 463 2009 influenza A (H1N1), 1,785 influenza A (H3N2), and750 influenza B virus samples have been tested for resistance to neuraminidaseinhibitors. While the vast majority of the tested virus samples (>99%) showedsusceptibility to the antiviral drugs oseltamivir and zanamivir, two 2009 H1N1viruses (reported during week 3 and week 6) and two influenza A (H3N2) viruses(reported during weeks 10 and 11) showed resistance to oseltamivir. High levels ofresistance to the adamantanes (amantadine and rimantadine) persist among 2009influenza A (H1N1) and A (H3N2) viruses. Adamantanes are not effective againstinfluenza B viruses.FluView is available – and past issues are archived – on the CDC website.Note: Delays in reporting may mean that data changes over time. The most up to datedata for all weeks during the 2012-2013 season can be found on the current FluViewwebpage at‐Related Pediatric Death Five pediatric deaths were reported during the week of March 31 – April 6, 2013.A total of 116 influenza-associated pediatric deaths have been reported during the2012-2013 season from Chicago [1], New York City [4] and 36 states (AL [1], AR[4], AZ [2], CA [3], CO [5], FL [8], HI [1], IA [1], IL [1], IN [4], KS [2], KY [1], LA[1], MA [3], MD [2], ME [1], MI [6], MN [4], MS [1], NE [1], NH [3], NJ [7], NM [2],NV [1], NY [7], OH [4], OK [1], PA [1], SC [4], SD [2], TN [2], TX [16], UT [3], VA[1], WA [1], and WI [4]).A pediatric death is a death in a person younger than 18 who died from an illnessrelated to infection with an influenza virus.A preliminary review of the available 2012-2013 pediatric death reports indicatesthat:3

CDC Influenza Division Key PointsApril 12, 2013ooo60% of deaths occurred in children who were at high risk of developingserious flu-related complications. However, 40% had no recognized chronichealth problems.About 90% of flu-related deaths were in unvaccinated children.The proportions of pediatric deaths that occurred in unvaccinated children andamong children at high risk from flu complications are largely consistent withwhat has been seen in the past.Since 2004, when pediatric deaths associated with influenza infection became anationally notifiable condition, the number of deaths reported to CDC each year hasranged from 34 (2011-2012 season) to 122 deaths (2010-2011 season). During the 2009 H1N1 pandemic — April 15, 2009 to October 2, 2010 — 348pediatric deaths were reported to CDC.These deaths are a somber reminder of the danger flu poses to children.The single best way to protect against seasonal flu and its potential severeconsequences is to have children receive a seasonal flu vaccine each year.Vaccination is especially important for children younger than 5 years of age andchildren of any age with an underlying medical condition like asthma, a neurologicalor neurodevelopmental disease, or immune suppression. These children are at higherrisk of serious complications if they get the flu.Information about the pediatric deaths, including basic demographics, underlyingconditions and time and place of death, is collected through the Influenza-AssociatedPediatric Mortality Surveillance System. Information for the 2012-2013 season isnow available through the Influenza Associated Pediatric Mortality application ofFluView Interactive at vaccination also is especially important for people in contact with high riskchildren in order to protect the child (or children) from the flu.Even previously healthy children can become seriously ill if they get the flu. Thelatest laboratory-confirmed influenza hospitalization data reported in this week’sFluView indicate that approximately 44% of children hospitalized with the flu had noidentified underlying medical conditions.Flu-related deaths in children younger than 18 years old should be reported throughthe Influenza-Associated Pediatric Mortality Surveillance System. The number of fluassociateddeaths among children reported during the 2012-2013 flu season will beupdated each week and can be found at Antiviral Treatment RecommendationsClinical benefit is greatest when antiviral treatment is administered early. Whenindicated, antiviral treatment should be started as soon as possible after illnessonset, ideally within 48 hours of symptom onset. However, antiviral treatment might4

CDC Influenza Division Key PointsApril 12, 2013still be beneficial in patients with severe, complicated or progressive illness and inhospitalized patients when started after 48 hours of illness onset, as indicated byobservational studies.Antiviral treatment is recommended as early as possible for any patient withconfirmed or suspected influenza whoooois hospitalized;has severe, complicated, or progressive illness; oris at higher risk for influenza complications.Treatment of persons with suspected influenza should not wait for laboratoryconfirmation of influenza. While influenza vaccination is the first and best way toprevent influenza, a history of influenza vaccination does not rule out the possibilityof influenza virus infection in an ill patient with clinical signs and symptomscompatible with influenza.Antiviral treatment also can be considered for any previously healthy, symptomaticoutpatient not at high risk with confirmed or suspected influenza on the basis ofclinical judgment, if treatment can be initiated within 48 hours of illness onset.More information is available at to Health Care Providers: Ordering Flu Vaccine for 2013‐2014The 2013-2014 influenza vaccine can be ordered at this time from manufacturersand distributors.As the 2012-2013 flu season has shown, it is important to pre-book vaccine as soonas it is available.Most of the flu vaccine offered for the 2013-2014 season will be trivalent (threecomponent).Some quadrivalent (four-component) vaccine will be available as well according tomanufacturers; however, supplies are expected to be limited.All nasal spray vaccine is expected to be quadrivalent, however, this makes up only asmall portion of total vaccine availability.oOrdering flu vaccine should not be delayed if quadrivalent flu vaccine is notavailable.Trivalent vaccine offers important protection from flu.Human Infections of Avian Influenza A (H7N9) in ChinaCases of human infection with a new avian influenza A (H7N9) virus continue to bedetected in China.5

CDC Influenza Division Key PointsApril 12, 2013The first human infections with H7N9 were reported by the Chinese National Healthand Family Planning Commission to the World Health Organization (WHO), whichformally reported these cases on April 1, 2013. (Updates on additional cases and theongoing epidemiological investigation are being posted on the WHO website.)A total of 43 cases of human infection with this new H7N9 have now been detected— and officially reported by — China. These cases all come from four adjacentprovinces in China.There are no reported cases of H7N9 in the United States or anywhere else outsideof China.A few of the infected people in China have had mild illness, but most of illnessassociated with these infections has been severe so far; 11 people have reportedlydied.Since this H7N9 virus is a novel influenza virus with pandemic potential, the situationin China is being carefully investigated.After the first human infections with H7N9 were detected, Chinese authoritiesdetected H7N9 viruses in poultry in the same area where human infections haveoccurred.The extent of the avian outbreak in poultry is still being assessed; but China hasreportedly begun culling birds in live markets.Many of the human cases of H7N9 are reported to have had contact with poultry;however, some cases reportedly have not had such contact.China is conducting follow-up investigations among close contacts of people infectedwith H7N9 to try to assess whether human-to-human spread of this virus isoccurring.These investigations suggest that there is no sustained (ongoing) spread of this virusfrom person to person at this time.Human infections with avian influenza viruses are rare and most often occur afterpeople are in contact with an infected bird.However, non-sustained person-to-person spread of other avian influenza viruses isthought to have occurred in the past, most notably with H5N1 viruses.Based on this previous experience with other avian influenza viruses, it’s likely thatsome limited human-to-human spread of this H7N9 virus will be detected.However, it’s important to remember that human-to-human transmission rangesalong a continuum; from occasional, “dead-end” human-to-human transmission, toefficient and sustained human-to-human transmission.“Dead end” transmission usually refers to when a virus from an animal host infects aperson and then there is some subsequent transmission that eventually burns out.For example, when a host infects one person who then subsequently infects someoneelse that is called “first generation spread.” If that second person then infectssomeone else that is called “second generation spread,” and so forth.Previously, third generation transmission of H5N1 viruses has been documented inone instance at least (Pakistan). (WHO, Weekly Epidemiological Record. “Humancases of avian influenza A(H5N1) in North-West Frontier Province, Pakistan,October–November 2007.”)6

CDC Influenza Division Key PointsApril 12, 2013However, efficient and sustained (ongoing) transmission in the community is neededfor an influenza pandemic to begin.There is no evidence that the H7N9 virus in China is spreading in a sustained,ongoing way at this time.On Friday, April 12, 2013, CDC posted a Flu Spotlight: “Additional H7N9 CasesReported in China; CDC Receives H7N9 Virus Isolate.” The spotlight is available at will provide updated information about H7N9 cases as it becomes available at On April 11, 2013, the New England Journal of Medicine published two piecesrelated to H7N9 influenza.ooAn article entitled “Human Infection with a Novel Avian-Origin Influenza A(H7N9) Virus” describes the epidemiologic, clinical and laboratory analysis ofthe first three human cases of avian influenza A (H7N9) virus infectiondetected in China.A commentary by CDC authors entitled, “Global Concerns Regarding NovelInfluenza A (H7N9) Virus Infections,” identifies some unique characteristics ofH7N9 influenza and highlights CDC’s preparedness efforts to learn more aboutH7N9 and its potential as a public health threat.7

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