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What's New with the Flu?

New clinical information and updated preventive, diagnostic, and therapeutic recommendations geared for pediatricians

As the 2009–2010 influenza season approaches, the CDC and others continue to report new clinical information as it becomes available and update preventive, diagnostic, and therapeutic recommendations.

The most recent clinical update adds to our understanding of a possible presentation of H1N1 influenza. The Dallas County Department of Health and Human Services reported four cases in children (age range, 7–17 years; all male) hospitalized for H1N1-associated neurological complications between May 18 and 28, 2009. None of the children had comorbidities. Of those with neurological complications, one patient had a seizure only, two had encephalopathy only, and one had both complications. Cerebrospinal fluid parameters were normal, except for slightly elevated protein in one patient and mild hypoglycorrhachia in another. In all patients, electroencephalograms showed abnormal slowing without epileptogenic foci, and head computed tomography scans were normal. All patients recovered fully.

The CDC has issued an update to the 2009 recommendations for the prevention and control of seasonal influenza with vaccines. Annual vaccination of all children ages 6 months to 18 years is now recommended (it was previously strongly encouraged), and the virus strains in the vaccine for the 2009–2010 flu season are provided. More updates will follow when information about H1N1 vaccination is available (see http://www.cdc.gov/flu for periodic updates).

Rapid diagnosis of influenza in the acute care setting helps determine the best type of therapy for patients. For those with a positive influenza test, antivirals may be appropriate. The ability to identify that patients have a documented nonbacterial source might allow us to decrease unnecessary antibiotic use. Office-based rapid flu tests are now available. The CDC tested the sensitivity of three rapid tests in 65 specimens known to contain seasonal or H1N1 swine influenza; 45 specimens were known to contain novel influenza A (H1N1). Compared with results of real-time reverse transcription–polymerase chain reaction (PCR) assay, the specificity among rapid tests for H1N1 specimens with high viral titers (9 specimens) ranged from 89% to 100%, but the overall sensitivity for H1N1 ranged from 40% to 69%. For seasonal flu, sensitivity ranged from 60% to 83%.

As the season approaches when we expect to see both seasonal influenza and novel H1N1 circulating simultaneously, data concerning treatment and prophylaxis are critical. A meta-analysis of data from randomized trials of neuraminidase inhibitors (oseltamivir or zanamivir) for treatment of seasonal flu in 1766 children and postexposure prophylaxis in 863 children revealed the following findings: Symptoms resolved about 1 day earlier with treatment, neuraminidase inhibitors did not lessen asthma exacerbations but conferred about an 8% reduction in risk for seasonal flu when used as prophylaxis, and oseltamivir increased the risk for vomiting. Studies of the efficacy of these drugs in novel H1N1 are not available.

As children return to school, the CDC has issued guidelines for state and local public health officers and school administrators in decision making regarding schools' responses to influenza. Details are provided at the U.S. government's Flu.gov site. Although guidelines differ depending on the severity of the flu season, all approaches stress respiratory etiquette, hand hygiene, and social distancing for those who are ill.

Comment: Practitioners should be aware that encephalopathy and encephalitis have been reported with standard seasonal influenza. As in any flu season, testing for influenza may be appropriate when a child presents with neurological symptoms and no other obvious etiology. However, testing also has its limitations. Therefore, when flu tests are negative and clinical suspicion remains high, PCR testing is available through some clinical labs and public health departments. Treatment remains the most difficult issue. No studies have addressed treatment during a season in which both seasonal influenza (which may be resistant to oseltamivir) and novel H1N1 are prevalent. If both viruses are circulating and the only available information is that a patient has influenza type A, the patient would need to be treated with either zanamivir (for patients >7 years) or a combination of oseltamivir and an adamantine. Therefore, I would reserve therapy for high-risk populations because the benefit in otherwise healthy children is not dramatic. The CDC will continue to develop new therapy guidelines as more information about circulating strains becomes available. Because H1N1 has gained vast media and public attention, serious symptoms are likely to cause great concern among parents. When asked about H1N1 and complications, physicians can use the opportunity to explain that seasonal flu presents similar risks and encourage compliance with CDC recommendations for universal pediatric vaccination. Assuming that the H1N1 vaccine will be available in adequate supply, children are a priority for receiving this vaccine as well.

— Peggy Sue Weintrub, MD

Dr. Weintrub is on the speaker's bureau for MedImmune.

Published in Journal Watch Pediatrics and Adolescent Medicine August 21, 2009

Citation(s):

Centers for Disease Control and Prevention (CDC). Neurologic complications associated with novel influenza A (H1N1) virus infection in children — Dallas, Texas, May 2009. MMWR Morb Mortal Wkly Rep 2009 Jul 24; 58:773.

• Medline abstract (Free)

Fiore AE et al. Prevention and control of seasonal influenza with vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2009. MMWR Recomm Rep 2009 Jul 31; 58:1. (http://www.cdc.gov/mmwr/preview/mmwrhtml/rr58e0724a1.htm)

• Medline abstract (Free)

Centers for Disease Control and Prevention (CDC). Evaluation of rapid influenza diagnostic tests for detection of novel influenza A (H1N1) virus — United States, 2009. MMWR Morb Mortal Wkly Rep 2009 Aug 7; 58:826.

• Medline abstract (Free)

Shun-Shin M et al. Neuraminidase inhibitors for treatment and prophylaxis of influenza in children: Systematic review and meta-analysis of randomised controlled trials. BMJ 2009 Aug 10; 339:b3172.

• Original article (Subscription may be required)
• Medline abstract (Free)

Reader Remarks:

Read all Reader Remarks on this article

• Office-based rapid flu tests
  John V. Carvalho, Apollo Safety, Inc., 31 Aug 2009 3:05 PM EST
  Please keep focus and frequent updates on "Office-based rapid flu tests" availabilty as this will be the most effective method... [more]
• H1N1 Vaccine
  E. Michael Linzey, 31 Aug 2009 3:05 PM EST
  Should pregnant women recieve vaccine when available???
• JWPAM response on vaccinating pregnant women
  Lyn Whinston-Perry, JW Pediatr Adolesc Med, Executive Editor, 31 Aug 2009 4:31 PM EST
  For a recent summary on pregnancy and the flu see http://womens-health.jwatch.org/cgi/content/full/2009/806/2