Severe H1N1 Infection in Children Linked to Asthma and Other Diseases

From Medscape Medical News
Barbara Boughton

September 17, 2009 (San Francisco, California) — Although most cases of H1N1 influenza are mild and self-limited, severe disease in children is most likely linked to underlying conditions such as asthma, according to Canadian research presented here at the 49th Interscience Conference on Antimicrobial Agents and Chemotherapy.

In the retrospective review, the case records of 89 children hospitalized with H1N1 were analyzed, and the researchers found that a "disturbing" number of children had serious complications requiring a stay in the intensive-care unit (ICU), said Bruce Tapiero, MD, from the Division of Infectious Diseases, Department of Pediatrics, CHU Sainte-Justine in Montreal, Quebec.

In the study, researchers identified 80 children, of the 89 cases reviewed, who were admitted to Sainte-Justine Hospital with confirmed H1N1, as defined by a positive PCR test. Most of the children hospitalized were older than 6 years, and many were school-aged.

One or more underlying medical conditions was found in 66% of the children, with the most common being asthma, sickle cell disease, and encephalopathy. Other underlying conditions were pneumonia and congenital heart disease.

Although most of the children displayed the usual features of H1N1 —fever, cough, and sore throat — a striking number also had gastrointestinal symptoms (49%). In fact, the 1 death that occurred from H1N1 was attributed to gastrointestinal complications, underlying lung disease, and encephalopathy.

Fever was seen in most of the children, and neurological features of the disease were common, with 7 children experiencing febrile seizures. In addition, 35% of the children had oxygen-saturation levels below 95%, and 4 of the sickest patients required mechanical ventilation.

Thirteen of the children (16%) required admission to the ICU, and most of those children had underlying comorbidities. The findings suggest that the infection might be particularly severe in these children, the investigators say. Despite the severity of illness, length of stay in the ICU was brief. Most of the children did not have extended stays in the hospital. The mean hospitalization for the group was 4 days.

The Canadian team noted that some lessons could be drawn from their study. Most children with H1N1, even those who are hospitalized, have moderate disease, they note. However, gastrointestinal symptoms and febrile seizures are prevalent in children with H1N1. Thus, it is important that clinicians pay attention to these symptoms when evaluating children for H1N1 to improve diagnosis and treatment, the researchers advise.

"This was a descriptive study, so it had some limitations," said Laurent Kaiser, MD, from University Hospital of Switzerland in Geneva, who moderated the session at which the study was presented. "But it shows us some interesting features of children with the most severe disease," he said.

"At the same time, we don't really have documentation about how widespread the disease is in children," Dr. Kaiser said. That kind of information can only come from large national studies, he explained. "What we're seeing here is the tip of the iceberg, but we don't really know the size of the iceberg yet because it's such a new disease."

49th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC): Presentation V-1269d. Presented September 14, 2009.