Clinical presentations of pandemic 2009 influenza A (H1N1) virus infection in hospitalized Thai children.

BACKGROUND

A novel influenza A (H1N1) virus of swine origin caused human infection and acute respiratory illness in Mexico during the spring of 2009. After that, the virus spread globally, resulting in the influenza pandemic.

OBJECTIVE

To observe the clinical manifestations of the 2009 pandemic influenza A (H1N1) and the epidemic waves of hospitalized children for a period of one year.

METHODS

A prospective observational study of children under eighteen years old, confirmed having the 2009 pandemic influenza (H1N1) infection by real-time reverse-transcription-polymerase-chain-reaction (RT-PCR), admitted at Queen Sirikit National Institute of Child Health, Bangkok, Thailand during one year, from 1st June 2009 to 31st May 2010.

RESULTS

A total of 83 pandemic influenza infected children were admitted during a one-year period. There were two waves of epidemic outbreak, the first wave from June to August 2009 and the second wave from January to February 2010. There were 47 cases of males (56.6%), with the highest attack rates among children 1-5 years of age (48.2%). The youngest case was a 29-day old girl. The correct provisional diagnosis of pandemic influenza infection are 39.5%, the other initial diagnosis are pneumonia, bronchiolitis, tonsillitis, encephalitis, and dengue infection. Most patients coming for care had typical, influenza-like symptoms with fever (98.8%), cough (92.6%) and rhinorrhea (74.1%). Systemic symptoms are frequent. Gastrointestinal symptoms (including vomiting (46.9%) and diarrhea (24.7%)) occur more commonly than seasonal influenza. Pneumonia is the most common complication (43.2%); other complications include bronchiolitis, hemoptysis, acute respiratory distress syndrome (ARDS) and encephalitis. In one case, a seven year old girl suffered from ARDS, sepsis, multi-organ dysfunction syndrome and ventilator associated pneumonia, but survived with some neurological sequelae. Radiographic findings included diffuse interstitial, alveolar infiltrates and some in lobar distributions. Apart from oseltamivir the other antibiotics included ceftriaxone, cefotaxime, amplicillin and azithromycin, were added for pneumonia. All patients in the present study survived.

CONCLUSIONS

The burden and character of pandemic influenza infection in developing countries are still incompletely understood. Early therapy with oseltamivir in severely ill patients, without waiting for laboratory confirmation for diagnosis, will save patients from severe complications.