Comparative dynamics, morbidity and mortality burden of pediatric viral respiratory infections in an equatorial city

Abstract

Background: Although acute respiratory infections (ARIs) are the global leading cause of pediatric morbidity and mortality, the relative impact of viral pathogens on pediatric ARIs is still poorly understood, especially in equatorial settings. Long-term studies of multiple viruses concurrently circulating in these regions are still lacking. Here, we report the results of a systematic prospective surveillance of multiple respiratory viruses conducted every weekday for nearly a decade in an equatorial city in Brazil.

Methods: We analyzed the relative burden of influenza, parainfluenza, respiratory syncytial virus (RSV), adenovirus, and metapneumovirus, their seasonality, and their association with climatic and demographic factors, ARI diagnosis, and pediatric mortality.

Results and conclusions: RSV was the primary driver of severe childhood respiratory infections, including pneumonia. RSV was also the virus most strongly associated with respiratory-associated deaths, with RSV circulation and pediatric mortality being in phase. Annual circulation of influenza peaked much earlier than annual mortality due to respiratory causes. The results also show that viral circulation can be strongly seasonal even in equatorial regions, which lack seasons with low temperatures: RSV and influenza were concentrated in the rainy season, whereas parainfluenza predominantly circulated in the dry season. The consistent epidemiologic patterns observed can be used for an effective adjustment of the timing of therapeutic and prophylactic interventions in this and potentially in other equatorial regions.

Figure 1

Map of Fortaleza. Panels on the right show mean temperature and precipitation (2001–2008, INMET), and humidity (vapor pressure, 2001–2005, CRU).

Figure 2

Age distribution of children diagnosed with ARIs by viral cause. Bars show the proportion of each virus associated to URTIs (left) and LRTIs (right) in each age class (from 0.5 to >= 4.5 years). Colors: black=RSV; dark grey=influenza; light grey=parainfluenza; white=adenovirus; patterned=metapneumovirus.

Figure 3

Number of weekly viral isolation rates for each viral pathogen. Colors: black=RSV; dark grey=influenza; light grey=parainfluenza; white=adenovirus; patterned=metapneumovirus. The bars also show the number of samples yielding negative results (patterned white on top).