WASHINGTON – Respiratory syncytial virus followed an epidemic pattern, particularly in infants, from May through July across 13 years, a study has shown.
The virus also was found more often in infants less than 3 months old who had bronchiolitis or hypoxemia at time of hospital admission, according to Dr. Maria F. Lucion, who presented the data during the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.
"This is a really valuable study with a very large number of cases. We don’t have a lot of information on this virus." Dr. Keith Klugman, director of global health at the Bill and Melinda Gates Foundation, Seattle, said during the discussion after the presentation.
Dr. Maria F. Lucion
From March 2000 to November 2013, 12,555 patients admitted for suspected acute lower respiratory infections to a single center in Argentina were tested for respiratory syncytial virus (RSV), adenovirus, influenza, and parainfluenza using either assays of nasopharyngeal aspirates or real-time polymerase chain reaction.
Of the 4,798 patients who tested positive for infection, 3,924 of all those admitted were found to have RSV (ranging between 71% and 82% across the years), with an annual seasonal epidemic pattern in evidence from May through July.
Independent predictors of RSV included being 3 months or younger (odds ratio 2.8, P less than .01); having bronchiolitis as a clinical presentation (OR 1.54, P less than .01); and the presence of hypoxemia at time of admission (OR 1.84, P less than .01), said Dr. Lucion of Ricardo Gutierrez Children’s Hospital, Buenos Aires.
The overall hospitalization rate for those with bronchiolitis was 39 per 1,000, with a peak in 2003 of 48 per 1,000. Bronchiolitis as a result of RSV was diagnosed in a median 15 patients per 1,000 (8.0-19.4).
The majority of admissions were male (56%), and the median age was 7 months, although nearly half (43%) were less than 6 months old (74.2% were less than 1 year old). Bronchiolitis occurred 61% of the time, and the nosocomial infection rate was 6.6%. The mortality rate was just under 2% (74/3,888).
"The most frequent complication was respiratory distress requiring the use of a ventilator," Dr. Lucion said. "That was most associated with the children who died."
An additional genetic analysis indicated that RSV subtypes A and B were in the pediatric population, with the exceptions of 2000 when only subtype A was present, and 2005, when only subtype B was present.
"The most common genotypes were GA2, GA5, ON1, and NA1 for subtype A and genotype-BA for subtype B," Dr. Lucion said.
Dr. Lucion said she had no relevant disclosures.
On Twitter @whitneymcknight