Viral Shedding Prolonged in Children With H1N1 Flu, Especially Younger Children

Alice Goodman

November 02, 2009

November 2, 2009 (Philadelphia, Pennsylvania) — Another piece of the H1N1 influenza puzzle emerged from a study showing that viral shedding is longer in children with the flu than in adults, and is longer in young children than in older children. The study was presented here at the Infectious Diseases Society of America (IDSA) 47th Annual Meeting.

The study, conducted in May 2009 during an outbreak of H1N1 influenza infection at a rural school in Pennsylvania, showed that the virus was detected up to 13 days after the onset of fever, and viable virus was detected by culture up to 6 days after onset of illness, even if there had been a resolution of fever.

The median duration of viral shedding after the onset of fever was 5 to 6 days, depending on the method used.

"This is one of the first studies to determine the length of viral shedding during the current pandemic, and will increase our understanding of the characteristics of this virus. These results should be interpreted cautiously, because detection of the virus does not necessary correlate with transmission of the virus to others," said Achuyt Bhattarai, MD, from the Centers for Disease Control and Prevention, in Atlanta, Georgia, who presented results.

The study examined 36 elementary-school students with sequentially obtained nasopharyngeal specimens within 7 days of influenza-like illness (temperature of 100 degrees Fahrenheit or greater, a cough, and/or a sore throat). The specimens were collected every 2 hours until they were no longer positive. Two different testing methods were used: real-time reverse-transcriptase polymerase chain reaction (rRT-PCR) to assess the presence of the viral genome and viral culture to assess the presence of viable H1N1 virus.

The analysis presented focused on 26 rRT-PCR-positive cases: 13 elementary-school children (aged 5 to 9 years) and 13 members of their households diagnosed with H1N1 flu. The median duration of viral shedding after the onset of fever, according to rRT-PCR, was 6 days (range, 1 to 13 days). The median duration of viral shedding after the onset of fever by culture was 5 days (range, 1 to 7 days). After resolution of fever, the median duration of shedding was 3 days according to rRT-PCR (range, 1 to 10 days) and 2 days according to culture (range, 1 to 5 days). Younger children had longer viral shedding than older children, but this difference was not statistically significant.

"Our findings on shedding duration are consistent with other studies of seasonal flu. We found that some people shed for 10 days or longer. Shedding duration should be incorporated into public health messaging," Dr. Bhattarai said.

Change in Visitation Policy at Hospitals

On the basis of this study and "the fact that the brunt of the cases are in children, we have re-examined our visitation policy at the Hospital of the University of Pennsylvania Heath System. With this pandemic, we don't have the luxury of waiting for the science to prove that viral shedding correlates with transmission. The theoretical concerns about transmission need to be balanced with practical issues for the safety of our patients and our employees," said Neil Fishman, MD, from the University of Pennsylvania Health System.

The visitation age is older than 16 years at the Hospital of the University of Pennsylvania and is above 18 at some hospitals in the United States.

Dr. Bhattarai and Dr. Fishman have disclosed no relevant financial relationships.

Infectious Diseases Society of America (IDSA) 47th Annual Meeting: Late-Breaker Abstract LB-47. Presented October 30, 2009.

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