Astrovirus often missed in infants with diarrhea worldwide

Reuters Health Information: Astrovirus often missed in infants with diarrhea worldwide

Astrovirus often missed in infants with diarrhea worldwide

Last Updated: 2017-12-19

By Marilynn Larkin

NEW YORK (Reuters Health) - Astrovirus is an underappreciated cause of diarrhea among infants worldwide and should be the focus of vaccine development, researchers suggest.

Dr. Margaret Kosek of Johns Hopkins Bloomberg School of Public Health in Baltimore told Reuters Health, "Astrovirus is consistently overlooked as an agent that causes acute gastroenteritis in children of similar severity to that of norovirus."

"In high-income countries, diagnostic tests are readily available yet underutilized," she said by email.

Dr. Kosek and colleagues analyzed data from the MAL-ED study, which enrolled infants within 17 days of birth in eight countries: Bangladesh, India, Nepal, Pakistan, Brazil, Peru, Tanzania and South Africa.

Children were managed through age two; stool samples were collected monthly the first year and quarterly thereafter for surveillance of enteric infections. Additional samples were obtained during diarrheal episodes, defined as three or more loose stools in a 24-hour period separated by at least two diarrhea-free days.

A total of 25,868 surveillance stools and 7,077 diarrheal stools from 2,082 children up to age two were collected for enteropathogen testing and longitudinal statistical analysis.

As reported online December 19 in Pediatrics, 35% of children experienced astrovirus infections. The prevalence in diarrheal stools was 5.6% (vs. 2.2% of surveillance stools), and the severity of astrovirus-related diarrhea exceeded that of all other enteropathogens except rotavirus.

The adjusted population-attributable fraction was 3.4%, which if applied to the estimated 1.73 billion annual diarrheal episodes worldwide suggests that astrovirus may account for up to 5.96 million cases annually.

Overall, 77% of all astrovirus-positive samples were coinfected with at least one other pathogen. The most common coinfection was with Campylobacter species, which were present in 28.7% of surveillance and 40.1% of diarrheal stools across the entire cohort. Other prevalent diarrhea-producing coinfections included norovirus, enteroaggregative Escherichia coli, and Giardia.

The incidences of infection and diarrhea per 100 child-months were 2.12 and 0.88 episodes, respectively. After adjustment for potential confounders, children with astrovirus infection had more than twice the odds of experiencing diarrhea.

Undernutrition was a risk factor: odds of infection and diarrhea were reduced by 10% and 13%, respectively, per increase in length-for-age z score.

Some evidence of protective immunity to infection was detected (hazard ratio, 0.84), although this was heterogeneous among sites and significant only in India and Peru.

Dr. Kosek said, "The evidence for acquired immunity in high-incidence areas combined with the disease burden warrant consideration of vaccine development for human astroviruses."

Dr. Adam Ratner, director of the Division of Pediatric Infectious Diseases at NYU Langone Health in New York City, told Reuters Health, "Childhood diarrhea remains an extremely important cause of childhood illness, hospitalization, and death, especially in medically under-resourced areas."

"This study provides crucial data from eight low- and middle-income countries . . . revealing that astrovirus, an often overlooked cause of disease, may be responsible for nearly 6 million cases of diarrhea annually, with greater frequency and increased severity in malnourished children," he said by email.

"Because current tests rarely look for astrovirus, it is likely that its importance has been underestimated to date," he added.

"There is no specific treatment for astrovirus, but prior exposure appears to decrease the odds of subsequent infections," he noted, "suggesting that an astrovirus vaccine may be feasible."

"Combined with vaccines targeting other common causes of childhood diarrhea, including rotavirus, an astrovirus vaccine could help decrease the substantial burden of disease in children worldwide," Dr. Ratner concluded.

SOURCE: http://bit.ly/2yXrADp

Pediatrics 2017.

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