Is It Viral Gastroenteritis? Maybe Check the Latest Weather Patterns

Knowing the recent outdoor temperatures could help clinicians decide whether a virus is behind a pediatric case of infectious gastroenteritis, according to a secondary analysis of a prospective trial.

Among over 800 children and adolescents who arrived at emergency departments with acute gastroenteritis, a 1 standard-deviation increase in average daily temperature over the prior 14 days was linked to a 50% lower chance that the gastroenteritis was caused by a virus (OR 0.50, 95% CI 0.36-0.68, P<0.001).

That significant inverse relationship between temperature and viral gastroenteritis was even stronger in older children. Compared with kids younger than 2 years, those ages 12 years and older were 83% less likely to have viral infectious gastroenteritis when the prior 2-week temps rose by 1 standard deviation (OR 0.17, 95% CI 0.09-0.33, P<0.001).

Unlike temperature, prior precipitation, humidity, and air pollution levels didn’t have a significant effect on viral gastroenteritis risk (P>0.05), reported Natalya Alekhina, PhD, of the University of Utah School of Medicine in Salt Lake City, and colleagues in Open Forum Infectious Diseases.

“Incorporating weather variables alongside other clinical and patient-level factors into clinical prediction tools may help prioritize diagnostic testing, minimize unnecessary antibiotic use, and improve the timely diagnosis and management of [infectious gastroenteritis],” they wrote.

A major cause of pediatric illness, infectious gastroenteritis is well known for its seasonal patterns. Viral infectious gastroenteritis is the most common type, including norovirus and rotavirus infections that typically peak during winter months. Lab diagnostic tests can help with management decisions, but excessive testing carries financial costs and could contribute to inappropriate antimicrobial use.

“As weather patterns vary year to year and with changing climate, weather-informed models are likely to prove superior to those based on season,” Alekhina and colleagues noted. “Weather-informed surveillance models can enhance the accuracy of seasonal outbreak predictions and optimize healthcare delivery during seasonal surges.”

The primary analysis of the prospective IMPACT study, which ran from March 2015 to August 2016, examined the clinical impact that routine molecular multiplex testing had on children presenting to the emergency department with acute gastroenteritis. The researchers found that the intervention was associated with a 21% reduction in the odds of any return visit (OR 0.79, 95% CI 0.70-0.90) after adjusting for potential confounders.

The current analysis included 868 IMPACT study patients who submitted a stool sample. Of that group, 38.8% had infectious gastroenteritis with viral-only etiology; 26.8% had nonviral or mixed virus, bacteria, or protozoa etiologies; and 34.3% didn’t have a detected pathogen. Most patients with viral infectious gastroenteritis were younger than 2 years (57.3%).

Alekhina and team repeated their individual-patient analysis using population-level surveillance data from GermWatch, a regional infectious disease system in Utah that aggregates stool sample testing in children and adults. GermWatch data also showed an inverse relationship between higher prior temperatures and lower percentages of viral infectious gastroenteritis.

In two Utah counties with the highest proportion of GermWatch stool testing, higher average monthly temperatures were significantly associated with a lower proportion of viral cases, with a 0.52-percentage point drop in the proportion of viral cases for every 1°F rise in mean temperature (P=0.002).

Study limitations included use of patient data from the continental U.S. and population-level data from Utah, which may limit the findings’ generalizability. The short duration of patient data also may have limited the ability to detect long-term seasonal patterns or rare events.