H1N1 flu increases complication in children with sickle cell anemia: Study

Children with sickle cell disease are especially hard-hit by the H1N1 flu strain, causing more life-threatening complications than the seasonal flu, according to a study from Johns Hopkins Children's Center.

The study's findings, published online July 23 in an early edition of the journal Blood, should be heeded as a warning call by parents and pediatricians that children with sickle cell anemia are more likely to need emergency treatment and to be hospitalized if they contract the H1N1 flu.

While H1N1 flu in the general population turned out to be much less severe than feared at the start of the 2009 pandemic, children with sickle cell disease remain at greater risk for complications from it, as well as other strains of the flu. A 2009 Hopkins Children's study found that children with sickle cell disease are hospitalized with seasonal flu nearly 80 times more often than other children.

Lead investigator John Strouse, M.D., Ph.D., a hematologist at Hopkins Children's says the study underscores the importance of timely immunization against both the H1N1 and the seasonal flu strains, which this year will be given in a single vaccine.

The Hopkins team analyzed the records of 123 children with sickle cell disease treated for any kind of flu at Hopkins Children's between September 1993 and December 10, 2009. Of them, 29 were infected with the H1N1 virus, a new strain that emerged for the first time in April of 2009.

While both the seasonal flu and the H1N1 virus caused most of the typical flu symptoms — fever, cough and a runny nose — in most of the children, sickle cell patients infected with H1N1 were nearly three times more likely to develop acute chest syndrome, a leading cause of death among such patients, marked by inflammation of the lungs, reduced ability to absorb oxygen and shortness of breath.

H1N1-infected children also were more than five times more likely to end up in the intensive-care unit than those with the regular flu, and they were overall more likely to need a ventilator for breathing.

Named for the unusually sickle-shaped red blood cells caused by an inherited abnormality, sickle cell anemia affects nearly 100,000 Americans, most of them African-American. The cells' abnormal structure reduces their oxygen delivery to vital organs and causes them to get stuck in the blood vessels, leading to severe pain and so-called "sickling crises," which require hospitalization.

The CDC estimates that up to one-fifth of Americans get the flu each year, resulting in 200,000 hospitalizations and 36,000 deaths.