February 17, 2007

Health Advisory: Update on Influenza-Associated Deaths

Since Feb 5, 2007, 2 pediatric deaths due to influenza-associated myocarditis have been confirmed in King County children 7 and 8 years of age, respectively. The King County Medical Examiner determined that a third death in a 7-year-old child on Feb. 17th was caused by bacterial pericarditis. This child had a history of influenza diagnosed by rapid antigen test by the child’s physician 3 days before death, which may have increased susceptibility to bacterial pericarditis. The children had no known contact with one another. Influenza activity is widespread throughout King County and it is not clear if the influenza season has peaked at this time. All age groups are being affected, but our monitoring suggests school-aged children and young adults are being impacted at higher levels than adults over 64 years of age and infants. School absenteeism and hospital emergency department visits have recently exceeded levels observed in recent influenza seasons.

With the exception of the deaths noted above, we have not observed an increase in hospitalizations for severe influenza-related complications, which appear similar to or lower than that seen in recent influenza seasons based on reports from area health care facilities and our syndromic surveillance monitoring. Influenza activity in Washington State and nationally has not been characterized as severe. This number of pediatric deaths in one year in King County is unusual, and Public Health is consulting with colleagues at the Federal Centers for Disease Control and Prevention and Washington State Department of Health about the illnesses. Thirteen pediatric deaths nationally have been reported to the U.S. Centers for Disease Control and Prevention so far this season compared to 41 total cases reported last year and 153 total cases reported in 2003. Key recommendations for healthcare providers follow.

• During influenza season, health care providers should be alert to the possibility of severe influenza-related complications in children and adults, particularly among persons with medical conditions (e.g., pulmonary or cardiac disease), including: secondary bacterial pneumonia or primary influenza viral pneumonia, and co-infection with other viral or bacterial pathogens. Influenza infection also has been uncommonly associated with encephalopathy, transverse myelitis, myositis, myocarditis, pericarditis, and Reye syndrome.
  
  
• Persons suspected to have severe complications of influenza inflection should be promptly evaluated in an emergency department.
  
  
• Signs of myocarditis include difficulty breathing, orthopnea, chest pain, grunting, abdominal pain, increasing weakness, pallor, diaphoresis, clammy skin, cool extremities, and sub-normal body temperature. When myocarditis is suspected, immediate emergency room evaluation and consultation with an expert in pediatric cardiology is recommended. Information on viral myocarditis from Children's Hospital and Regional Medical Center is provided below.

In both recent pediatric influenza-associated myocarditis deaths in King County, the parents reported a relatively sudden onset of high fever on the first day of illness, followed 1-2 days later by a period of cool extremities and low temperature, rising again to a low grade fever before death. Both children had significant weakness on the 2nd or 3rd day of illness; one was unable to walk. One child had severe myalgias. The other had no myalgias but did have abdominal pain and vomiting. In both cases, the parents reported that the child was alert with normal mental status until minutes before decompensation and death. Both children had coughing, but neither child had wheezing or rash. On post mortem examination, neither child had evidence of pneumonia or pulmonary edema.

• Data are limited regarding the effectiveness of antiviral agents in preventing serious influenza-related complications. Healthcare providers should test patients with ILI for influenza when possible and consider antiviral treatment of patients with positive rapid influenza test results, particularly patients at high risk for severe influenza-related complications. When influenza activity in the community is at high levels, treatment can be considered for patients suspected to have influenza on clinical grounds if rapid testing is not available. Initiation of antiviral treatment within 2 days of illness onset is recommended.
  
  
• Oseltamivir or zanamivir can be prescribed if antiviral treatment of influenza is indicated, amantadine and rimantidne are not recommended because of widespread resistance to these agents. Oseltamivir is approved for treatment of persons aged > 1 year, and zanamivir is approved for treatment of persons aged > 7 years. Oseltamivir and zanamivir can be used for chemoprophylaxis of influenza; oseltamivir is licensed for use in persons aged > 1 year, and zanamivir is licensed for use in persons aged > 5 years. For additional information on use of antiviral drugs and for a recent FDA precaution related to oseltamivir, see: www.cdc.gov/flu/professionals/treatment
  
  
• Public Health continues to recommend influenza vaccine for all high risk groups, their household members and close contacts, and anyone else who wishes to reduce their risk of getting influenza. Flu vaccine is currently available in the community. Public Health is planning to hold walk-in influenza vaccination clinics at Public Health clinic sites on Sunday, Feb. 18th and Monday, Feb. 19th. Vaccine will also be available next week at Public Health clinic sites. Check the Public Health website at www.metrokc.gov/health/immunization/fluseason for details and information about flu vaccine availability and clinic locations in King County.
  
  
• Healthcare providers and facilities should report all suspected influenza-related deaths and unusual serious complications to Public Health at 207-296-4774.

Viral myocarditis is a rare but serious complication of influenza and other viral infections. Myocarditis can lead to acute heart failure culminating in cardiogenic shock, ventricular arrhythmias, or pericardial effusion. This complication is generally treated with supportive care at a cardiac specialty care center. Early warning signs may include, but are not limited to:

In addition to a very thorough history and examination, the following tests are suggested:

If a pediatric patent's cardiac status is compromised by influenza or there is suspicion of myocarditis or heart failure (regardless of the result of any specific test result), the child should be transferred to a tertiary pediatric cardiac care center.