Viruses Associated With Acute Respiratory Infections and Influenza-like Illness Among Outpatients From the Influenza Incidence Surveillance Project, 2010–2011

Abstract

Background The Influenza Incidence Surveillance Project (IISP) monitored outpatient acute respiratory infection (ARI; defined as the presence of ≥2 respiratory symptoms not meeting ILI criteria) and influenza-like illness (ILI) to determine the incidence and contribution of associated viral etiologies. Methods From August 2010 through July 2011, 57 outpatient healthcare providers in 12 US sites reported weekly the number of visits for ILI and ARI and collected respiratory specimens on a subset for viral testing. The incidence was estimated using the number of patients in the practice as the denominator, and the virus-specific incidence of clinic visits was extrapolated from the proportion of patients testing positive. Results The age-adjusted cumulative incidence of outpatient visits for ARI and ILI combined was 95/1000 persons, with a viral etiology identified in 58% of specimens. Most frequently detected were rhinoviruses/enteroviruses (RV/EV) (21%) and influenza viruses (21%); the resulting extrapolated incidence of outpatient visits was 20 and 19/1000 persons respectively. The incidence of influenza virus-associated clinic visits was highest among patients aged 2–17 years, whereas other viruses had varied patterns among age groups. Conclusions The IISP provides a unique opportunity to estimate the outpatient respiratory illness burden by etiology. Influenza virus infection and RV/EV infection(s) represent a substantial burden of respiratory disease in the US outpatient setting, particularly among children.

Enteroviruses and Rhinoviruses: Molecular Epidemiology of the Most Influenza-Like Illness Associated Viruses in Senegal

“…25 In a large study in outpatients with ILI from the United States, HRVs/HEVs were the most commonly detected viruses (after influenza), with an overall detection rate of 21%. 26 The findings of these different studies are in broad agreement with those presented herein.…”

Viral etiology in adult influenza-like illness/acute respiratory infection and predictivity of C-reactive protein

“…This difference may be due to the non-temperate climate in our region, as higher activity of influenza virus can be encountered in regions with a humid climate [21]. On the other hand, our rhinovirus detection rates were very close to those of influenza virus, and our results agreed with a large IISP of outpatients from the United States in that the predominant virus was influenza, closely followed by rhinovirus, among adult patients 18-64 years of age [2].…”

“…Although bacterial etiology might sometimes be encountered, the majority of ILI cases are caused by viral pathogens [1]. Epidemic peaks during the winter months are usually caused by influenza virus and respiratory syncytial virus (RSV), while other viruses such as human metapneumovirus (MPV) and parainfluenza viruses (PIVs) also circulate in fall and winter [2]. There is a corresponding winter increase in presentations to emergency departments and outpatient clinics [3,4].…”

An Under-Recognized Influenza Epidemic Identified by Rapid Influenza Testing, Southern Sri Lanka, 2013

“…The percentage of ILI was similar to that in other settings-in the United States, the national baseline among outpatients is 2.0%, with increases up to 4.6% during seasonal peaks. 12,13 There are few published data regarding patterns of influenza in Sri Lanka, but surveillance samples tested by the national reference laboratory, Medical Research Institute (MRI), showed that the prevalence of laboratory-confirmed influenza among outpatients presenting with ILI to sentinel hospital sites was 12% in 2011 and 16% in 2012. 14 The proportion of influenza in this study was much higher than documented in prior years and was initially largely under recognized, which highlights the need for continued surveillance and testing from all regions of the country.…”