Autor(es):
Cristóvão, Paula 
; Pechirra, Pedro ; Machado, Ausenda ; Nunes, Baltazar ; Conde, Patrícia ; Guiomar, Raquel
Data: 2013
Identificador Persistente: http://hdl.handle.net/10400.18/1726
Origem: Repositório Científico do Instituto Nacional de Saúde
Assunto(s): Infecções Respiratórias; Gripe; Vírus Respiratórios; Diagnóstico Diferencial; Estados de Saúde e de Doença
Descrição
Respiratory viral disease is a serious public health problem globally with considerable social and economic impacts. Respiratory viruses cause respiratory disease that ranges from mild to severe pneumonia, contributing for morbidity and mortality throughout the world. The etiological diagnosis based on clinical presentation is very difficult due to the similarity of clinical presentation of respiratory viral infections. In order to have a more complete knowledge on the viral etiology of influenza like illness in Portugal, a search for viral agents (including influenza) was done in the framework of the National Influenza Surveillance System, from season 2010/2011 to 2012/2013.
During the 3 winter seasons cases of influenza like illness (ILI) according to the EU case definition were notified by the sentinel and non-sentinel networks. For each studied case a nasopharyngeal swab collected in the first seven days after symptoms onset was received in the National Influenza Reference Laboratory. A multiplex real time PCR for influenza detection was performed for all the samples. All the influenza A were subtyped using the Prodesse Proflu+ - GeneProbe, Inc., and influenza B lineage was determined using the WHO recommended protocol. The other respiratory viruses: human rhinovirus, respiratory sincicial virus A and B, parainfluenza virus 1, 2 and 3, adenovirus and metapneumovirus were detected by a multiplex real time PCR, allowing detection of multiple infections. From the first winter, 2010/2011, a random selection of 378 ILI cases (taking into account the time and age distribution of cases representing 37.2% of the reported cases) was analyzed. In the following seasons 2011/2012 and 2012/2013 all samples were tested for influenza and other respiratory viruses, corresponding to 678 cases and 1256 cases, respectively. For the 2012-13 season the odds ratio (OR) of being positive for specific respiratory virus for each sign/symptom was calculated.
A total of 2312 samples were analyzed for the 3 seasons.. In each season the causal agent was identified in 68%, 52% and 62% of the samples.
The flu virus was the most frequently detected agent accounting for 53.4%, 37.5% and 43.0% of the cases analyzed. In co-circulation with influenza, hRV and RSV were detected in the highest percentage of cases. The PIV, hMPV and AdV virus were detected sporadically. There were cases of mixed infections of 2 or more viruses (representing 1-2%), mostly associated with the influenza virus. In the three seasons the highest percentage of positive cases was detected in children between 0-4 years. hRV was detected throughout the winter, while the RSV circulated simultaneously with the influenza virus.
In the 2012-13 season and considering signs and symptoms more associated to Influenza virus, significant association was found with fever (OR=3.13; 95%CI: 1.89–5.19), and cough (OR=3.94; 95%CI:2.52–6.16). These results were similar if we consider the influenza sub-types A(H1)pdm09 (Fever: OR=2.82; 95%CI:1.4–5.66; Cough: OR=5.43; 95%CI:2.36–12.48) and B Yamagata lineage (Fever: OR=2.24; 95%CI:1.23-4,07; Cough: OR=1.74; 95%CI:1,05– 2.88). For hRV only fever (OR=0.45; 95%CI:0.26-0,79) and sore throat (OR= 2,85; 95%CI:1,51 - 5,39) were significantly associated, whilst for RSV only sore throat was associated (OR= 2.23; 95%CI: 1,05-4,72). For the remaining respiratory virus (PIV, hMPV and AdV virus) chills was the only symptom associated (OR= 4.04; 95%CI: 1.22–13.35).
The detection of other respiratory viruses enabled the laboratory diagnosis of more than 50 % of ILI cases. The other respiratory viruses accounted for 10-15% of the ILI positives, with greater prevalence for hRV and RSV. Influenza and RSV co-circulated in the 3 winter as described before for other countries. For the majority of the investigated respiratory virus the presence of one or two signs or symptom was associated to be positive for that virus, These included fever/ cough (Influenza), sore throat (RSV) and chills (PIV, hMPV and AdV virus). The absence of fever was associated to the detection of the hRV.
