A 28-year study of human parainfluenza in Rio Grande do Sul, Southern Brazil

Abstract

Problem: Human parainfluenza virus (hPIV) is an important pathogen in respiratory infections, however the health burden of hPIV is underestimated. This study describes the infections by hPIV1-3 in Rio Grande do Sul, Brazil, from 1990 to 2017, providing data of the frequency and seasonality of cases and associated clinical symptoms.

Method of study: Nasopharyngeal samples of patients with respiratory infection were collected, clinical data were analyzed, and immunofluorescence was used to detect hPIV.

Results: Respiratory viruses were detected in 33.63% of respiratory infections. In a total of 11 606 cases of viral respiratory infection, 781 were positive for hPIV; hPIV prevalence ranged from 2.14% to 27% of viral respiratory infections. hPIV1 circulates mainly during fall; hPIV3 circulation, in turn, starts in fall and peaks during spring; and cases of hPIV2 are reported along the year, with peaks in fall and early spring. The most affected age group was children, with hPIV prevalence of 74.23% in patients for less than 1 year. A higher proportion of girls were infected than boys, however, no difference by sex was observed considering all age groups. The most frequent type was hPIV3, especially in hospitalized patients. Both hPIV1 and 3 were associated with dyspnea, while hPIV2 caused mild symptoms mainly in nonhospitalized patients. Nineteen fatalities occurred, 89.5% of them associated with risk factors (prematurity; chronic diseases; age, <1 or >60 years).

Conclusion: hPIV causes a high number of respiratory infections, leading to hospitalization especially in children; epidemiological and surveillance studies are important for the control and management of respiratory infections.

Keywords: acute respiratory infection; hPIV infection; respiratory virus; severe acute respiratory infection.

Figure 1

Total number of cases positive for respiratory viruses in Rio Grande do Sul (1990‐2017) and cases positive for each hPIV type. Between 1990 and 1999, only hPIV3 was tested; years from 2000 to 2017 include data for hPIV1‐3. hPIV: human parainfluenza virus

Figure 2

Total number of hPIV‐positive cases according to epidemiological weeks in Rio Grande do Sul (data accumulated monthly from 1990 to 2017); Max temp, average maximum temperature (in degrees Celsius) registered for each month during the period; Min temp, average minimum temperature (in degrees Celsius) registered for each month during the period. hPIV, human parainfluenza virus

Figure 3

Distribution of patients with ARI (A) or SARI (B) according to age groups. ARI, acute respiratory infection; hPIV, human parainfluenza virus; SARI, severe acute respiratory infection