Respiratory Viral Pathogens in Children Evaluated at Military Treatment Facilities in Oahu, Hawaii From 2014 to 2018: Seasonality and Climatic Factors

Determining the timing of respiratory syncytial virus (RSV) epidemics: a systematic review, 2016 to 2021; method categorisation and identification of influencing factors

BackgroundThere is currently no standardised approach to estimate respiratory syncytial virus (RSV) epidemics' timing (or seasonality), a critical information for their effective prevention and control.AimWe aimed to provide an overview of methods to define RSV seasonality and identify factors supporting method choice or interpretation/comparison of seasonal estimates.MethodsWe systematically searched PubMed and Embase (2016-2021) for studies using quantitative approaches to determine the start and end of RSV epidemics. Studies' features (data-collection purpose, location, regional/(sub)national scope), methods, and assessment characteristics (case definitions, sampled population's age, in/outpatient status, setting, diagnostics) were extracted. Methods were categorised by their need of a denominator (i.e. numbers of specimens tested) and their retrospective vs real-time application. Factors worth considering when choosing methods and assessing seasonal estimates were sought by analysing studies.ResultsWe included 32 articles presenting 49 seasonality estimates (18 thereof through the 10% positivity threshold method). Methods were classified into eight categories, two requiring a denominator (1 retrospective; 1 real-time) and six not (3 retrospective; 3 real-time). A wide range of assessment characteristics was observed. Several studies showed that seasonality estimates varied when methods differed, or data with dissimilar assessment characteristics were employed. Five factors (comprising study purpose, application time, assessment characteristics, healthcare system and policies, and context) were identified that could support method choice and result interpretation.ConclusionMethods and assessment characteristics used to define RSV seasonality are heterogeneous. Our categorisation of methods and proposed framework of factors may assist in choosing RSV seasonality methods and interpretating results.

Seasonality and Climatic Factors Associated With Human Rhinovirus/Enterovirus Nasopharyngeal Sample Positivity on Oahu, Hawai'i, 2016-2019

INTRODUCTION

Globally, human rhinoviruses/enteroviruses (HRVs/ENTs), indistinguishable on many widely available molecular platforms, are among the leading causes of the common cold. Geographic and climatic factors impact the peak activity of these viruses. In temperate climates, the peak activity of HRV occurs during autumn and spring whereas that of ENT occurs during autumn and summer. Both viruses are thought to peak during the rainy season in tropical climates like Hawai'i; however, data remain limited. We describe HRV/ENT seasonality and evaluate the climatic factors associated with peak activity among respiratory viral samples processed on Oahu, Hawai'i.

MATERIALS AND METHODS

We conducted a retrospective analysis of all respiratory specimens submitted to Tripler Army Medical Center for multiplex polymerase chain reaction testing between May 2016 and May 2019. Among HRV/ENT-positive samples, we recorded the month and year of positivity. Summative monthly positive detection was calculated with peak months above the mean. Associations between temperature, precipitation levels, relative humidity, and wind speed by week and the number of positive samples for HRV/ENT were evaluated using Poisson regression. This analysis was conducted via IRB exempt protocol number 19R18.

RESULTS

During our study period, there were 7,143 nasopharyngeal respiratory samples sent for multiplex polymerase chain reaction testing, with 1,572 positive for HRV/ENT (22%). Nineteen percent of respiratory samples positive for HRV/ENT were additionally positive for one or more respiratory pathogens. The majority of HRV/ENT-positive samples arose from children < 5 years of age (n = 959, 61%). Peak months were February, March, May, August, November, and December. After controlling for lagged count and year, average wind speed was the only climatic factor significantly associated with HRV/ENT sample positivity.

CONCLUSIONS

The peak monthly activity of HRV/ENT was similar to temperate climates with the exception of peak activity in February. Unlike other tropical climates, lower wind speed was associated with increased weekly HRV/ENT positivity and should be further explored as a transmission factor. Our study contributes to understanding the annual variability of HRV/ENT activity in tropical environments, which can inform clinician expectations regarding respiratory viral symptomatology in this region.

Respiratory Viral Pathogens Among U.S. Military Personnel at a Medical Treatment Facility in Hawaii From 2014 to 2019

INTRODUCTION

Acute respiratory diseases account for a substantial number of outpatient visits and hospitalizations among U.S. military personnel, significantly affecting mission readiness and military operations. We conducted a retrospective analysis of respiratory viral pathogen (RVP) samples collected from U.S. military personnel stationed in Hawaii and tested at Tripler Army Medical Center from January 2014 to May 2019 in order to describe the etiology, distribution, and seasonality of RVP exposure in a military population.

MATERIALS AND METHODS

Samples were analyzed by viral culture or multiplex PCR. Distribution of respiratory viruses over time was analyzed as well as subject demographic and encounter data. Presenting signs and symptoms were evaluated with each RVP.

RESULTS

A total of 2,576 military personnel were tested, of which 726 (28.2%) were positive for one or more RVP. Among positive tests, the three most common viral pathogens detected were influenza A (43.0%), rhinovirus (24.5%), and parainfluenza (7.6%). Symptoms were generally mild and most frequently included cough, fever, and body aches.

CONCLUSION

Our study evaluated respiratory virus prevalence, seasonality, and association with clinical symptoms for military personnel in an urban tropical setting in Oahu, HI, over a 5-year period. We show that viral prevalence and seasonality in Hawaii are distinct from those of the CONUS. Results contribute to the broader understanding of seasonality, clinical manifestation, and demographics of RVP among active duty military personnel stationed in Hawaii.