Epidemiological aspects of influenza A related to climatic conditions during and after a pandemic period in the city of Salvador, northeastern Brazil

Abstract

During the influenza pandemic of 2009, the A(H1N1)pdm09, A/H3N2 seasonal and influenza B viruses were observed to be co-circulating with other respiratory viruses. To observe the epidemiological pattern of the influenza virus between May 2009-August 2011, 467 nasopharyngeal aspirates were collected from children less than five years of age in the city of Salvador. In addition, data on weather conditions were obtained. Indirect immunofluorescence, real-time transcription reverse polymerase chain reaction (RT-PCR), and sequencing assays were performed for influenza virus detection. Of all 467 samples, 34 (7%) specimens were positive for influenza A and of these, viral characterisation identified Flu A/H3N2 in 25/34 (74%) and A(H1N1)pdm09 in 9/34 (26%). Influenza B accounted for a small proportion (0.8%) and the other respiratory viruses for 27.2% (127/467). No deaths were registered and no pattern of seasonality or expected climatic conditions could be established. These observations are important for predicting the evolution of epidemics and in implementing future anti-pandemic measures.

A Descriptive Study of Pandemic Influenza A(h1n1)pdm09 in Brazil, 2009 - 2010

“…As a result of our study, among the total of reported cases, the highest frequency occurred in females, children and young adults who are white, with an educational level of completed high school and residents in urban areas were the most frequently notified, as well as confirmed cases of influenza A(H1N1)pdm09 were found. Such findings are supported by results of other authors 20,21,[23][24][25][26][27][28] .…”

“…The national tendency is that the influenza virus spreads in the south and southeast regions during winter (June-August) and in the north and northeast regions, during rainy periods. However, in tropical and subtropical countries, there may be peaks during the year in the dynamics of the seasonal influenza A; some authors suggest that this behavior is associated with climate aspects (temperature, humidity), solar radiation, possibly with levels of vitamin D, the host immunity and the virulence of the viral strain 23 .…”

Relative frequency, Possible Risk Factors, Viral Codetection Rates, and Seasonality of Respiratory Syncytial Virus Among Children With Lower Respiratory Tract Infection in Northeastern Brazil

“…16 This same group also reported their attempt to investigate parainfluenza infections among children from Fortaleza, 22 as well as adenovirus infections in Salvador. 23 Silva et al 24 assessed the prevalence of influenza viruses among children in Salvador. RSV infects virtually every child in the 1st few years of life and is the most important cause of hospitalization for respiratory infection in young children worldwide.…”

“…10,13,20 Only a few studies were conducted to investigate the prevalence and seasonal patterns of different viral infections among children with an episode of LRTI seen at hospitals from Northeastern Brazil, where the winter is warm and wet. 14,16,[21][22][23][24] Such studies were typically conducted in only 1 major city in the region and have not allowed for concurrent assessments within different areas of the Northeastern region of Brazil. Moreover, they have used different eligibility criteria and methods for viral identification.…”

Pathogen transcriptional profile in nasopharyngeal aspirates of children with acute respiratory tract infection

“…We observed a good agreement between Real-Time PCR and nCounter for RSV (A and B) detection, reinforcing the possibility of using the latter as an alternative method for pathogen detection. Of note, RSVA strains present a high variability in the target used for detection (G protein domain) [13], also in Brazil [6], which could explain the weaker correlation observed for nCounter and Real-Time PCR, as compared to RSVB.…”