Younger children with influenza A (H1N1) may have longer viral shedding than older children, adults

Influenza A (H1N1) virus was detected by real time reverse transcriptase polymerase chain reaction in patients up to 13 days after onset of fever, according to results presented at the 47th Annual Meeting of the Infectious Diseases Society of America.

The results were presented by Achuyt Bhattarai, MD, an Epidemic Intelligence Service Officer at CDC.

The researchers conducted a telephone survey to identify elementary school students or household contacts of elementary school students with influenza-like illness onset within seven days of the survey. The study was conducted in May - June 2009 in Pennsylvania.

Among 36 specimens from students or contacts with influenza-like illness, 26 were identified as having 2009 H1N1 by real-time reverse transcriptase-polymerase chain reaction (PCR) test. Specimens were also tested by viral culture for the presence of H1N1.

Further analysis by real-time PCR determined that the median duration of viral shedding was six days (range 1 to 13 days) after the onset of fever. Further analysis by culture determined that the median duration that viable H1N1 was detected was five days (range 1 to 7 days) after the onset of fever.

Real-time PCR detected virus for a median of three days following the resolution of fever. Virus was detected by culture an average of two days after the resolution of fever.

“In our study, younger children were observed to have prolonged viral shedding, as compared to older children and adults, which is consistent with earlier studies of seasonal influenza,” Bhattarai said. “However, I would like to emphasize that the results of our study should be interpreted carefully, because detection of virus may not mean that patients are likely to transmit the virus to others.

“This was one of the first studies to determine the duration of viral shedding during the current pandemic and one of the first among children,” Bhattarai said.