Comparison of the Outcomes of Individuals With Medically Attended Influenza A and B Virus Infections Enrolled in 2 International Cohort Studies Over a 6-Year Period: 2009–2015
Authors: Dwyer Dominic E , Lynfield Ruth , Losso Marcelo H , Davey Richard T , Cozzi-Lepri Alessandro , Wentworth Deborah , Uyeki Timothy M , Gordin Fred , Angus Brian , Qvist Tavs , Emery Sean , Lundgren Jens , Neaton James D ,   INSIGHT Influenza Study Group, Aagaard Bitten , Borges Álvaro H D , Cozzi-Lepri Alessandro , Eid Marius , Jansson Per O , Jeppesen Marianne , Joensen Zillah Maria , Pedersen Ruth Kjærgaard , Lundgren Jens , Nielsen Birgit Riis , Pearson Mary , Peters Lars , Qvist Tavs , Angus Brian , Babiker Abdel , Bennett Rachel , Braimah Nafisah , Collaco-Moraes Yolanda , Cursley Adam , Hudson Fleur , Pett Sarah , Russell Charlotte , Webb Helen , Carey Dianne , Courtney-Rodgers David , Emery Sean , Shaw Pamela , Gordin Fred , Sanchez Adriana , Standridge Barbara , Vjecha Michael , Brekke Kate , Campbell Megan , Denning Eileen , DuChene Alain , Engen Nicole , George Michelle , Harrison Merrie , Neaton James D , Nelson Ray , Quan Siu-Fun , Schultz Terri , Wentworth Deborah , Baxter John , Brown Shawn , Hoover Marie , Beigel John , Davey Richard T , Dewar Robin , Gover Erin , McConnell Rose , Metcalf Julia , Natarajan Ven , Rehman Tauseef , Voell Jocelyn , Dwyer Dominic E , Kok Jen , Uyeki Timothy M , Munroe David , Aguila Damian , Alzogaray Maria Fernanda , Ballesteros Maria Fernanda , Barcan Laura , Barcelona Laura , Belloso Waldo , Berdiñas Veronica , Bonvehi Pablo , Caeiro Juan Pablo , Cisneros Veronica , Crinejo Ana , David Daniel , Doldan Luz , Ebenrstejin Juan , Lipari Flavio , Lopardo Ana , Lopardo Gustavo , Losso Marcelo , Lucchetti Pablo , Lupo Sergio , Macias Laura Moreno , de Tesco Alejandra Moricz , Mykietiuk Analia , Nannini Estaban , Nieto Gabriel , Nieto Laura , Peroni Luciana , Retta Ignacio , Rodriguez Patricia , Sanchez Marisa , Sanchez Pablo , de Paz Sierra Mariana , Tavella Silvina , Temporiti Elena , Trape Liliana , Vieni Ines , Warley Eduardo , Yahni Diego , Zarate Abel Humberto , Avihingsanon Anchalee , Charoentonpuban Kanlaya , Chetchotisakd Ploenchan , Kaewon Peeraporn , Laopraynak Naphassanant , Manosuthi Weerawat , Pussadee Kanitta , Putcharoen Opass , Ruxrungtham Kiat , Suwanpimonkul Gompol , Ubolyam Sasiwimol , Arduino Roberto , Atkinson Barbara , Aulicino Taryn M , Baker Jason V , Bardascino Cindy , Bass Caitlin , Baxter John D , Beilke Mark , Bentley Beverly D , Lee Bertrand Mary , Brown Ann B , Carbonneau June , Cindrich Richard , Coburn Patty , Cohen Calvin J , Clark Linda , Cummins Shirley , Dassow Paul , DeHovitz Jack A , Dharan Nila J , Faber Leslie , Farrough Marti , Freiberg Matthew , Gardner Edward , Jo Garrett Kimberly , Geisler Christiane , Glesby Marshall , Green Julia , Grenade Joanne , Gunderson Edie , Gunter John , Ham Kirsis , Holman Susan , Hughes Valery , Hurt Christopher , Johnson Mary , Koerbel Glory , Koletar Susan , Lan Audrey , MacArthur Rodger , Marcus Cheryl , Markowitz Norm , Martinez Maria Laura , McLaughlin Karen , Nahra Raquel , Nettles Mary Jane , Nixon Daniel , Novak Richard , Nuffer Kathleen , Olivet Hannah B , Omotosho Bola , Paez Armando P , Paez-Quinde Marta , Parker Sonija , Patil Namrata , Polenakovik Hari , Powell Sandra , Prosser Rachel A , Reilly Nancy A , Riska Paul F , Rizza Stacey , Schooley Robert , Schwarber Marla , Scott James , Simon Gary L , Sivoravong Jon , Skiest Daniel J , Solorzano Clemencia , Sondengam Rita , Swanson Nicole , Tedaldi Ellen , Temesgen Zelalem , Thomas Doug , Thron Bill , Traverse Colleen , Uddin David E , Uslan Daniel Z , Vasco Marina , Vaughan William M , Vecino Isabel , Wade Barbara , Walker Catrice , Watson Kathy , Watson Vicky , Wohl David , Wolfe Cameron R , Andry Leslie , Bielen Mireille , Clumeck Nathan , Florence Eric , Kabeya Kabamba , Sagaer Jolanthe , Weckx Jozef , Anagnostou Olga , Antoniadou Anastasia , Daikos George , Gioukari Vicky , Kalomenidis Ioannis , Kantzanou Maria , Koratzanis Georgios , Koulouris Nikolaos , Maltezos Efstratios , Metallidis Symeon , Polixronopoulos Vlassis , Sambatakou Helen , Skoutelis Athanasios , Touloumi Giota , Vasilopoulos Nikolaos , Bloch Mark , Cunningham Nicky , Dwyer Dominic E , Edwards Sian , Elliott Julian , Garlick Jill , Habel Philip , Kilkenny Fiona , Lau Helen , MacRae Karen , McBride John , Moore Richard , Prone Isabel , Ram Ristila , Richmond Sue , Roth Norm , Meng Soo Tuck , Jo-Anne Thompson , Vincent Trina , Vlakahis Emanuel , Woolstencroft Rachel , Chadwick David , Clarke Tristan , Democratis Jane , Dockrell David , Heyderman Robert , Jeffs Ben , Kutter Stefan , Llewelyn Martin , Minton Jane , Newport Melanie , Price Ashley , Benites Carlos , Castillo Raul , Chinchay Romina , Cornelio Eva , Guevara Maria , Gutierrez Luis , Hidalgo Jose , La Rosa Alberto , Pinedo Yvett , Saenz Maria , Vega Juan , Baadegaard Bente , Bach Karen , Collins Philippa , Gerstoft Jan , Hergens Lene , Jensen Lene Pors , Joensen Zillah Maria , Kronborg Gitte , Loftheim Iben Rose , Nielsen Henrik , Oestergaard Lars , Pedersen Court , Stauning Pedersen Jens Aage , Yehdego Yordanos , Bergmann Frank , Boesecke Christoph , Bogner Johannes R , Brockmeyer Norbert , Czaja-Harder Christine , Draenert Rika , Fätkenheuer Gerd , Klinker Hartwig , Kümmerle Tim , Lehmann Clara , Müller Vera , Plettenberg Andreas , Rockstroh Jürgen , Schlabe Stefan , E Schmidt Wolfgang , Schürmann Dirk , Schüttfort Gundolf , Seybold Ulrich , Stephan Christoph , Stoehr Albrecht , Tillmann Klaus , Wiebecke Susanne , Wolf Timo , Arribas Jose , Carbone Javier , Fernández Cruz Eduardo , Dalmau David , Estrada Vincente , Herrero Patricia , Knobel Hernando , López Paco , Montejano Rocío , Sans Moreno José , Ramón Paño José , Portas Begoña , Rodrigo Maria , Romero Pilar , Sánchez-Sendín Domingo , Soriano Vincente , Bakowska Elzbieta , Horban Andrzej Jerzy , Knysz Brygida , Kowalska Karolina Pyziak , Zubkiewicz-Zarebska Anna , Kase Kerstin , Mülle Helen , Zilmer Kai , Allendes Gladys , Flores Jimena , Northland Rebeka , Perez Carlos , Velasco Isabel , Wolff Marcelo , Chu Man-Yee , Wu Tak-chiu , Burgmann Heinz , Tobudic Selma , Imahashi Mayumi , Imamura Junji , Iwatani Yasumasa , Kogure Ayumi , Nakahata Masashi , Sugiura Wataru , Yokomaku Yoshiyuki , Maagaard Anne 
Published: March 2018

Abstract

Background
Outcome data from prospective follow-up studies comparing infections with different influenza virus types/subtypes are limited.

Methods
Demographic, clinical characteristics and follow-up outcomes for adults with laboratory-confirmed influenza A(H1N1)pdm09, A(H3N2), or B virus infections were compared in 2 prospective cohorts enrolled globally from 2009 through 2015. Logistic regression was used to compare outcomes among influenza virus type/subtypes.

Results
Of 3952 outpatients, 1290 (32.6%) had A(H1N1)pdm09 virus infection, 1857 (47.0%) had A(H3N2), and 805 (20.4%) had influenza B. Of 1398 inpatients, 641 (45.8%) had A(H1N1)pdm09, 532 (38.1%) had A(H3N2), and 225 (16.1%) had influenza B. Outpatients with A(H1N1)pdm09 were younger with fewer comorbidities and were more likely to be hospitalized during the 14-day follow-up (3.3%) than influenza B (2.2%) or A(H3N2) (0.7%; P &lt; .0001). Hospitalized patients with A(H1N1)pdm09 (20.3%) were more likely to be enrolled from intensive care units (ICUs) than those with A(H3N2) (11.3%) or B (9.8%; P &lt; .0001). However, 60-day follow-up of discharged inpatients showed no difference in disease progression (P = .32) or all-cause mortality (P = .30) among influenza types/subtypes. These findings were consistent after covariate adjustment, in sensitivity analyses, and for subgroups defined by age, enrollment location, and comorbidities.

Conclusions
Outpatients infected with influenza A(H1N1)pdm09 or influenza B were more likely to be hospitalized than those with A(H3N2). Hospitalized patients infected with A(H1N1)pdm09 were younger and more likely to have severe disease at study entry (measured by ICU enrollment), but did not have worse 60-day outcomes.