Children with respiratory illnesses had multiple viruses

51st ICAAC

CHICAGO — About half of children with respiratory illnesses at a daycare center had multiple viral infections during their illness, according to findings presented at the 51st Interscience Conference on Antimicrobial Agents and Chemotherapy held here.

Emily T. Martin, PhD, assistant professor in the Department of Pharmacy Practice at Wayne State University in Detroit, said that the study involved 225 children.

“We designed the study to look at the distribution of viruses in this population now that we have the technology to detect more viruses than ever before,” she said. “What surprised us was that 55% of illnesses that involved a virus had more than one virus detected.”

Martin said that the study took advantage of PCR to gain more exact epidemiological perspective.

“Because of all the viruses detected, we weren’t able to do the traditional epidemiology we have done in the past, where these were the kids in the respiratory syncytial virus (RSV) bucket and those were the kids in the influenza bucket.”

Martin said that the researchers were also surprised that more viruses were appearing throughout the study period.

“Maybe they would start with adenovirus, but by the second week they may have had a rhinovirus,” she said. “The viruses were shifting and changing throughout the illness, which made it difficult to characterize it as whatever was detected at the beginning.”

Eligible children were aged 1 to 24 months. Every time a child had a respiratory illness, the study nurse tested the child when the illness started and then every week after until the illness was resolved, according to Martin.

The researchers prospectively followed the patients for up to 2 years. PCR was used to test the swabs for human metapneumovirus, RSV, parainfluenza types 1-4, influenza A and B, rhinoviruses, coronaviruses, human bocavirus-1 and adenoviruses.

There were 466 new-onset illnesses captured and analyzed. At least one respiratory virus was detected in 82% of these illnesses and multiple viruses were detected in 45%. The maximum number of viruses detected during the same illness was five.

Rhinovirus illnesses had a 66% specific coinfection rate, and adenovirus illnesses had an 87% coinfection rate.

Variation was observed in the detection of specific viruses at onset of illness. This resulted in differences in prevalence of individual viruses based on the time since illness onset. For example, 98% of RSV detections occurred when illness symptoms began, but only 78% of adenovirus detections occurred at illness onset (P<.001).

Severity of illness symptoms decreased when viral coinfections occurred. Children with a single virus had increased rates of fever compared with children with multiple viruses (OR=0.6; 95% CI, 0.35-0.88).

“A high proportion of respiratory illnesses in daycare attendees had multiple viruses detected during the course of illness,” the researchers wrote. “Delay between onset of illness and viral detection varied by virus, indicating that [adenovirus] and other viruses may be underrepresented in studies of virus epidemiology that use only a single test at symptom onset.”— by Rob Volansky

Disclosures: Dr. Martin reports no financial disclosures. The study was partially funded by MedImmune.

For more information:

Martin ET. #G3-185. Epidemiology of Respiratory Viral Coinfections in Daycare Attendees. Presented at: 51st ICAAC. Sept. 17-20, 2011. Chicago.

Follow the PediatricSuperSite.com on Twitter.