Study: Most flu cases in small children missed

Jul 7, 2006 (CIDRAP News) – Physicians miss the diagnosis of influenza in children under age 5 most of the time, according to researchers who tested thousands of sick children for flu in three US counties over several years.

Healthcare providers identified flu in only 28% of young children who were hospitalized because of the illness and in only 17% of those who were treated in a clinic or hospital emergency department, according to a report in the Jul 6 New England Journal of Medicine.

The failure to recognize flu means children are not getting antiviral drugs that could ease their symptoms, especially if given in the first 2 days of illness. About 35% of the sick children in the study saw a healthcare provider within the first 2 days of symptom onset.

"This lack of recognition represents a missed opportunity to reduce both the risk of complications and the spread of the virus to contacts," writes W. Paul Glezen, MD, in an editorial accompanying the report.

The study also indicated that outpatient visits related to flu were between 10 and 250 times as common as flu-related hospitalizations, suggesting that increased flu immunization could reduce medical visits and costs.

The report comes in the wake of a new federal recommendation that all 2-, 3-, and 4-year-olds should be vaccinated against flu every year. The same recommendation was made 2 years ago for children between 6 and 23 months old.

The study involved prospective testing of children who were hospitalized or received outpatient treatment for acute respiratory tract infection or fever in three urban counties. The New Vaccine Surveillance Network, set up in 1999 by the Centers for Disease Control and Prevention, conducted the study, with Katherine M. Poehling, MD, of Vanderbilt University as first author.

The hospital component of the study ran from October 2000 through September 2004 in Rochester, N.Y., and Nashville, and from October 2003 through September 2004 in Cincinnati. The outpatient part of the study was done in selected clinics and emergency departments during the 2002-03 and 2003-04 flu seasons in Nashville and Rochester and in 2003-04 in Cincinnati.

The researchers collected nasal and throat specimens from each child for testing by viral culture and reverse-transcriptase polymerase chain reaction.

Among 2,797 hospitalized children enrolled in the study, the authors found 160 (6%) laboratory-confirmed cases of flu. Only 28% of these had a flu diagnosis at the time of discharge (the surveillance test results were not available to clinicians before discharge). Only 52 of the 160 children diagnosed by the authors received a flu test as part of their clinical care, and 38 of these 52 tested positive, according to the report. Eighty percent (148) of the children with lab-confirmed flu were younger than 2 years.

The investigators calculated that the average rate of hospitalization for confirmed influenza among children under age 5 in the three counties was 0.9 per 1,000 children from 2000 to 2004 (95% confidence interval, 0.8 to 1.1 per 1,000). The hospitalization rates varied by age-group within that age range: 4.5 per 1,000 for children aged 0 to 5 months, 0.9 per 1,000 for ages 6 to 23 months, and 0.3 per 1,000 for those aged 24 to 59 months.

In the outpatient wing of the study, 1,742 children were enrolled, of whom 274 (16%) had lab-confirmed flu. Healthcare providers recognized flu in only 17% of these 274 children, according to the report.

Using their data, the authors estimated that 56 of every 1,000 children in the three counties were taken to a clinic or emergency department because of flu in 2002-03. In the 2003-04 season, the estimated number of visits jumped to 122 per 1,000. The rate of outpatient visits was highest in children 6 to 23 months old and lowest in those 0 to 5 months old.

"We found a much higher burden of influenza infection in the outpatient setting than in the inpatient setting, a large variation in burden according to the year and site, and a lack of clinical recognition of influenza during most visits," the authors write.

They found that about 35% of the children with flu were taken to a medical provider within 2 days after they became ill, "when antiviral medications may have shortened the duration and severity of illness," the report says. Increased use of rapid tests for influenza could not only increase the use of antivirals, but also improve infection control and boost the use of flu vaccine, the article states.

Noting that flu-related outpatient visits vastly outnumbered hospitalizations, the authors write, "Although the rationale for enhanced vaccination against influenza in children has been based primarily on hospitalization rates, reducing the number of outpatient visits attributable to the prevention of influenza by vaccination would have an even greater effect on costs."

In his editorial, Glezen, of Baylor College of Medicine in Houston, comments that children shed larger amounts of influenza virus for longer periods than adults do. "Treatment of these younger patients even three to four days after the onset of infection may at least reduce the spread of infection to contacts," he writes. He adds that when flu is recognized in a child, clinicians can offer preventive treatment to the child's family members.

Poehling KA, Edwards KM, Weinberg GA, et al. The underrecognized burden of influenza in young children. N Engl J Med 2006 Jul 6;355(1):31-40 [Abstract]

Glezen WP. Influenza control. (Editorial) N Engl J Med 2006 Jul 6;355(1):79-81 [Introduction]

Newsletter Sign-up

Get CIDRAP news and other free newsletters.

Sign up now»


Unrestricted financial support provided by

Bentson Foundation 3M Gilead 
Grant support for ASP provided by

  Become an underwriter»