Meteorological variables and occurrence of respiratory syncytial virus in Uruguay

Meteorological factors and respiratory syncytial virus seasonality in subtropical Australia

Evidence is emerging regarding the influence of meteorological factors on seasonal respiratory syncytial virus outbreaks. Data however, are limited for subtropical regions, especially in the southern hemisphere. We examined whether meteorological data (daily minimum and maximum temperatures, rainfall, relative humidity, dew point, daily global solar exposure) and tourist numbers were associated with the incidence of RSV in children aged <5 years for the Gold Coast region of South-East Queensland, Australia (latitude 28.0°S). RSV cases between 1 July 2007 and 30 June 2016 were identified from the Pathology Queensland Gold Coast Laboratory database. Time-series methods were used to identify seasonal patterns. RSV activity peaked in mid-to-late autumn (April–May), tapering in winter (June–August). While most meteorological variables measured were associated with RSV incidence, rainfall (ρ = 0.40, 95% confidence interval (CI) 0.32–0.48) and humidity (ρ = 0.38, 95% CI 0.29–0.46) 8 weeks earlier had the nearest temporal relationship. Tourist numbers were not correlated with RSV activity. Identifying meteorological conditions associated with seasonal RSV epidemics can improve understanding of virus transmission and assist planning for their impact upon the health sector, including timing of passive RSV immunoprophylaxis for high-risk infants and future public health interventions, such as maternal immunisation with RSV vaccines.

Influence of weather on incidence of bronchiolitis in Australia and New Zealand

AIM

We aimed to examine the impact of weather on hospital admissions with bronchiolitis in Australia and New Zealand.

METHODS

We collected data for inpatient admissions of infants aged 2-12 months to seven hospitals in four cities in Australia and New Zealand from 2009 until 2011. Correlation of hospital admissions with minimum daily temperature, wind speed, relative humidity and rainfall was examined using linear, Poisson and negative binomial regression analyses as well as general estimated equation models. To account for possible lag between exposure to weather and admission to hospital, analyses were conducted for time lags of 0-4 weeks.

RESULTS

During the study period, 3876 patients were admitted to the study hospitals. Hospital admissions showed strong seasonality with peaks in wintertime, onset in autumn and offset in spring. The onset of peak incidence was preceded by a drop in temperature. Minimum temperature was inversely correlated with hospital admissions, whereas wind speed was directly correlated. These correlations were sustained for time lags of up to 4 weeks. Standardised correlation coefficients ranged from -0.14 to -0.54 for minimum temperature and from 0.18 to 0.39 for wind speed. Relative humidity and rainfall showed no correlation with hospital admissions in our study.

CONCLUSION

A decrease in temperature and increasing wind speed are associated with increasing incidence of bronchiolitis hospital admissions in Australia and New Zealand.

Climatic factors and lower respiratory tract infection due to respiratory syncytial virus in hospitalised infants in northern Spain

OBJECTIVE

To analyse the influence of climatic factors on the number of hospitalised infants with respiratory syncytial virus (RSV) per week.

METHODS

A retrospective observational case-control study was designed enrolling infants under 2 years of age, admitted to hospital between October 1995 and June 2000 with lower respiratory tract infection due to RSV. Climatic and seasonal data were included. The week variable was used as the study unit: weeks with more than one admission for the case group and weeks without admissions for the control group. The total number of weeks excluding summer months, from June to September, was 174.

RESULTS

A total of 167 infants were admitted to hospital with lower respiratory tract infection due to RSV with a peak in January and February. There was 82 weeks with one or more admissions (case group) and 92 without admissions (control group). The case group demonstrated lower levels of humidity (absolute: 5.6 +/- 1.5 vs. 6.5 +/- 1.5; p < 0.001) and lower temperature (ground level: 0.4 +/- 3.2 vs. 2.2 +/- 3.5; p < 0.001). When climatic factors were analysed in a logistic regression model, absolute humidity (p < 0.001) was an independent variable associated with a higher risk of infection.

CONCLUSIONS

Low absolute humidity was independently associated with hospital admission of infants with lower respiratory tract infection due to RSV.

Current concepts on active immunization against respiratory syncytial virus for infants and young children

Respiratory syncytial virus (RSV) is the most important causative agent of viral respiratory tract infections in infants and young children. Passive immunization against RSV became available recently, but this does not apply to an effective vaccine as a result of dramatic adverse results of immunization with a RSV candidate vaccine in the 1960s and the lack of full knowledge of the immune response induced by RSV. Nonetheless intensive research during the past two decades has resulted in several interesting candidate vaccines, of which some have gone through testing in humans. These include the subunit vaccines PFP-1, PFP-2, BBG2Na and cold-passaged/temperature-sensitive mutants. The development of candidate vaccines against RSV is discussed. Because of questions, uncertainties and difficulties with the development of effective vaccines against RSV, it will probably be at least another 5 to 10 years before routine immunization against RSV becomes available.