Recent Influenza Research by the CDC Epidemic Intelligence Service

Public health leaders have serious concerns about influenza, according to Dan Jernigan, MD, MPH, director of the Centers for Disease Control and Prevention (CDC) Influenza Division during a session on influenza on May 2nd during the 65th Annual Epidemic Intelligence Service (EIS) Conference in Atlanta, Georgia.

“What scares Bill Gates is pandemic flu; it keeps him up at night,” Dr. Jernigan told his audience of CDC EIS officers and other public health professionals, adding that CDC director Tom Frieden, MD, MPH, has also said that the threat of influenza keeps him up at night.

“Influenza is something that, if it goes bad, it goes really bad,” he cautioned. Dr. Jernigan and Michael Jhung, MD, MPH, medical officer in the CDC Influenza Division, moderated presentations by EIS officers who are lead authors on recent clinical studies. The session takeaways are listed below:

Caitlin Pedati, MD, MPH, and her colleagues worked with the Nebraska Department of Health and Human Services and found that including more words in an electronic health record’s (EHR’s) chief complaint fields increases its ability to identify influenza-like illness (ILI). They recommend that EHR vendors provide larger data entry fields that can capture longer chief complaints to help public health workers detect, treat, and contain the spread of influenza in Nebraska.

The researchers reviewed 160 Emergency Department visits between January and March, 2015, and compared the accuracy of 6 words or fewer with 7 or more words in each chief complaint field of the ESSENCE (Electronic Surveillance System for Early Notification of Community-Based Epidemics) EHR. They also compared the agreement of ESSENCE’s results with the gold-standard manual review of each chart and found that the longer string of chief complaints matched more closely with the manual reviews. The overall sensitivity was 33%; 25% for 6 or fewer words; and 50% for 7 or more words. The respective specificities were 96%, 97%, and 96%.

Grace D. Appiah, MD, and colleagues found that adults 65 years of age and above, and those with high-risk conditions, are more likely to be hospitalized for influenza, which supports current recommendations that they receive outpatient antiviral treatment.

Her group reviewed the medical records of adult outpatients enrolled at five US Influenza Vaccine Effectiveness Network sites over the 2011-2012 through 2014-2015 flu seasons. The patients had lab-confirmed influenza and their respiratory illness had begun within the last week.

Overall, 73 (2%) of 4,024 adult outpatients with influenza were hospitalized for up to two weeks after their outpatient visit, including 5% of those 65 and above and 3% of those who had high-risk conditions.

In an interview on a related study presented in a poster, Dr. Appiah told Contagion™, “We found that, from the 2010-2011 until the 2014-2015 season, the use of antivirals across different age groups of hospitalized patients with flu increased, which was impressive and encouraging.”

“All patients with flu who are hospitalized should receive an antiviral whether or not test results are available. In those who are known to have flu, about 80% are being given an antiviral, but ideally this should be 100%. Clinicians should encourage patients to present early in their illness onset if they have a respiratory illness that could be flu and they should be encouraged to start their patients on an antiviral early because it can have a good clinical benefit,” she advised.

Rebekah S. Schicker, MSN, MPH, and her group also examined antiviral prescribing patterns. Although early antiviral treatment is recommended by the CDC for all outpatients at high risk for severe disease and can lower the risk of complications, including hospitalization and death, the authors found that among high-risk outpatients between the 2012-2013 through the 2014-2015 influenza seasons, the drugs were consistently under-prescribed. They recommend exploring the barriers to prescribing and increasing the use of antivirals in these patients.

The authors obtained clinical information, tested respiratory specimens for influenza, and analyzed antiviral prescription data for outpatients 6 months of age and older, with respiratory illness lasting one week or less, who were enrolled in the US Influenza Vaccine Effectiveness Network in five states.

Overall, 865 (8%) of 10,521 outpatients in high-risk groups, including those under two years of age, those 65 years of age and above, those with an underlying medical condition, and pregnant women were prescribed antiviral medications.

Clinicians need to be aware of the risk of multiple pathogens in severe acute respiratory illness (SARI) and consider adding influenza testing to their antiviral treatment during flu season, advised Kate E.R. Russell, MD, MPH, and her co-authors.

Minnesota conducted SARI surveillance in three hospitals from September 2013 through June 2015, testing respiratory specimens for 16 viral and 6 bacterial pathogens from all hospitalized patients with fever, cough, and difficulty breathing. They compared age-adjusted risk factors and outcomes of patients with influenza alone with those with co-detections.

Of 320 influenza virus-positive SARI patients, 70 (22%) had one or more co-detections (17% viral and 5% bacterial). Overall, respiratory syncytial virus and rhinovirus were most frequent and Staphylococcus aureus was the most common bacterial co-detection.

Patients with viral co-detections were younger than patients with influenza alone (median age 2 years vs 50 years respectively); patients with bacterial co-detections had higher mortality (18% vs 1%) and more frequent ICU admissions (35% vs 12%). They were also less likely to have had a clinician-ordered influenza test (odds ratio 0.40) and to have received influenza antiviral treatment (odds ratio 0.58).

In a study among young children in Bangladesh, Melissa A. Rolfes, PhD, MPH, and her team found that vaccinating them with trivalent inactivated influenza vaccine (IIV3) slightly reduced laboratory-confirmed influenza incidence but did not significantly affect pneumonia. They suggest exploring other vaccine and non-vaccine interventions to help protect children in low-income countries from flu and pneumonia.

They enrolled children from 6 to 23 months of age in a double-blind, randomized controlled trial comparing IIV3 with inactivated polio vaccine (IPV) between 2010 and 2014.

Overall, 2,576 and 2,593 child-years were observed in the IIV3 and IPV groups, respectively; pneumonia incidence was 46 episodes per 100 child-years in both groups (vaccine effectiveness [VE] against clinical pneumonia = -1%); influenza incidence was 9 and 14 episodes per 100 child-years in the IIV3 and IPV groups, respectively (VE against influenza = 32%); 4% of pneumonia episodes were influenza-positive (VE against influenza-positive pneumonia = 32%).

Lorraine L. Janeczko, MPH, is a medical science writer who creates news, continuing medical education and feature content in a wide range of specialties for clinicians, researchers and other readers. She has completed a Master of Public Health degree through the Department of Epidemiology of the Johns Hopkins Bloomberg School of Public Health and a Dana Postdoctoral Fellowship in Preventive Public Health Ophthalmology from the Wilmer Eye Institute, the Johns Hopkins University School of Medicine and the Bloomberg School.

SOURCE: EIS 2016 Conference Program, pp 40-42: Concurrent Session C2: Influenza

Studies Presented:

Caitlin Pedati, MD, MPH, EIS officer, Center for Surveillance, Epidemiology and Laboratory Services, Influence of Chief Complaint Field Length Concerning Syndromic Surveillance of Influenza-Like Illness — Nebraska, 2015

Rebekah S. Schicker, MPH, EIS officer, National Center for Immunization and Respiratory Diseases, Influenza Antiviral Use Among High-Risk Outpatients During Three Recent Influenza Seasons — United States, 2012—2015

Grace D. Appiah, MD, EIS officer, National Center for Immunization and Respiratory Diseases, Risk Factors for Hospital Admission Following Outpatient Medical Care Among Adults with Influenza — United States, 2011—2015

Grace D. Appiah, MD, EIS officer, National Center for Immunization and Respiratory Diseases, Increased Antiviral Treatment Among Hospitalized Children and Adults with Laboratory-Confirmed Influenza — United States, 2010—2014 (poster)

Kate E. R. Russell, MD, MPH, EIS officer, National Center for Immunization and Respiratory Diseases, Viral and Bacterial Co-detections in Influenza-Positive Patients Hospitalized with Severe Acute Respiratory Illness — Minnesota, 2013—2015

Melissa A. Rolfes, PhD, MPH, EIS officer, National Center for Immunization and Respiratory Diseases, Trivalent Inactivated Influenza Vaccine Efficacy Among Young Children in an Urban Bangladesh