Flu Spreads Further...And CDC Says Severe Pediatric Illness & Deaths Underscore Severe Consequences in Kids; Read CDC's Latest Update

[T]he 2003--04 influenza season began unusually early...[with] continued spread of influenza activity during the weeks ending October 4-December 6. National activity levels have not yet peaked...Influenza seasons dominated by A (H3N2) viruses...typically are associated with high levels of severe illness and deaths. No evidence exists to indicate that the A/Fujian-like viruses in circulation are more virulent than other influenza A (H3N2) viruses. However, reports of severe pediatric illnesses and deaths underscore the severe consequences that influenza infections can cause in children.

Cases of sudden death associated with influenza in previously healthy children also were reported in the United States during the 2002--03 season...Although the pathophysiology of sudden deaths associated with influenza in children is unknown, atypical symptoms (e.g., abdominal pain, absence of fever, and mild respiratory symptoms) have been reported.

Encephalopathy is another severe and potentially under-recognized complication of influenza in children. One case so far this season has resulted in the death of a patient. Patients might report high fevers, seizures, headaches, abnormal mental status, and/or confusion and do not always exhibit classic influenza symptoms. Cases have been reported among young children and school-aged children, including adolescents...

CDC has received reports of severe complications of influenza occurring in young infants, school-age children, and adolescents. Complications have included encephalopathy, seizures, dehydration with severe hypotension, respiratory failure requiring mechanical ventilation, and secondary bacterial pneumonia, including necrotizing pneumonia with community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA). Three deaths (an infant aged 20 months with underlying reactive airways disease, a previously healthy infant aged 22 months, and a previously healthy child aged 16 years) have been associated with secondary pneumonia caused by CA-MRSA. Other influenza-related deaths not related to CA-MRSA in children have occurred. Fatal cases reported to CDC are being investigated by local and state health authorities. Laboratory testing has confirmed influenza A virus infection in these fatal cases; antigenic characterization is pending. The vaccination status of the majority of the deceased children has not been determined.

The A/Fujian-like viruses [now predominating in the U.S.] are antigenic drift variants of the A/Panama strain and were detected by global surveillance early this year but too late for inclusion in the current influenza vaccine. Hemagglutination inhibition testing using postinfection ferret sera indicates that antibodies to the A/Panama vaccine virus cross-react with A/Fujian-like viruses; therefore, current influenza vaccines should provide some protection against A/Fujian-like viruses. However, the level of protection remains uncertain until vaccine effectiveness studies are completed. The vaccine also contains A/New Caledonia/20/99 (H1N1)-like and B/Hong Kong/330/2001-like viruses and should protect persons who are vaccinated against these viruses if they circulate more widely later in the season.

Influenza antiviral medications are available for use in adults and children. Four prescription antiviral medications (i.e., amantadine, rimantadine, oseltamivir, and zanamivir) are approved for treatment of influenza A virus infections. Oseltamivir and zanamivir also are approved for treatment of influenza B. The costs, routes of administration, adverse effects, contraindications, approved ages, and potential for antiviral resistance differ among the four drugs. When administered within 48 hours of symptom onset, antiviral treatment of influenza can reduce the duration of illness by approximately 1 day in healthy adults. Data on the use of any of the four antiviral agents during pregnancy are not available. Amantadine, rimantadine, and oseltamivir also are approved for chemoprophylaxis of influenza A virus infections and can be used for control of institutional influenza outbreaks. When used for chemoprophylaxis, antivirals can be approximately 70%--90% effective in preventing illness in healthy adults...

Vaccination

• Emphasis should be placed on targeting trivalent inactivated vaccine to persons at high risk for complications from influenza: healthy children aged 6-23 months, adults aged > 65 years, pregnant women in their second or third trimester during influenza season, and persons aged > 2 years with underlying chronic conditions.
• Persons at high risk should be encouraged to search locally for vaccine if their usual health-care provider no longer has vaccine available.
• All children at high risk, including those aged 6-23 months, who report for vaccination should be vaccinated with a first or second dose, depending on vaccination status. Doses should not be held in reserve to ensure that two doses will be available.
• Next priority should be given to vaccinating those persons at greatest risk for transmission of disease to persons at high risk, including household contacts and health-care workers.
• Healthy persons aged 5-49 years should be encouraged to be vaccinated with intranasally administered live, attenuated influenza vaccine.
• Decisions about vaccinating healthy persons, including adults aged 50-64 years, with inactivated influenza vaccine should be made on a case-by-case basis, depending on local disease activity, vaccine coverage, feasibility, and supply.
• Health departments should work with their health-care providers to reallocate influenza vaccine to health-care providers in need when possible.

Hygiene

Good respiratory hygiene should be encouraged, including cleaning of hands, and staying at home when symptomatic with fever and respiratory illness.

Medication

Antiviral medications with specific activity against influenza A viruses should be considered either for treatment or chemoprophylaxis for influenza A, especially in persons at high risk for complications from influenza. [see text above]