Children's flu cases turn deadly after bacterial infection

Jul 11, 2007 (CIDRAP News) – Health officials in Perth, Australia, last week advised parents to seek medical care quickly for young children with respiratory symptoms, after three children under age 5 died of pneumonia as a complication of "mild" influenza A infections.

Paul Van Buynder, director of communicable disease control for Western Australia's health department, said in a Jul 6 press release that officials were surprised by how quickly the illness developed in the children. "While we do not want to create unnecessary panic, it is important for parents to be aware that the disease can cause serious illness within 24 hours," he said.

The children who died had a streptococcal pneumonia infection, but health officials have not announced what type, according to a recent report from Australian Broadcasting Corporation News.

The cases started out as "mild influenza A infection," Van Buynder told the Australian Associated Press. He said the health department found no links between the children's cases. Australia is at the peak of its flu season, and the report said hospitals in the Perth area were inundated by anxious parents bringing children with flu symptoms.

News of the Australian cases comes as infectious disease and public health experts are worrying about the threat of a flu pandemic associated with H5N1 avian flu. In past flu pandemics, bacterial coinfections have contributed substantially to deaths.

The Australian report also is a reminder of recent worries US health officials have had about rising numbers of young flu patients who have suffered coinfections with the sometimes-fatal Staphylococcus aureus pneumonia, in some cases involving drug-resistant strains.

S aureus can cause a severe, necrotizing pneumonia that has a relatively high case-fatality rate—33% during the 1968-69 flu pandemic, the CDC said in an Apr 13 Morbidity and Mortality Weekly Report article that detailed some of the recent fatal cases.

Evidence points to a synergistic relationship between S aureus and influenza, according to an article in the June 2006 issue of Emerging Infectious Diseases. Flu viruses appear to increase S aureus adhesion in the respiratory tract, and S aureus-specific enzymes (proteases) appear to increase flu virus replication. Also, influenza A virus strains appear to decrease destruction of S aureus by immune cells called phagocytes, making patients more susceptible to bacterial coinfection.

In May the US Centers for Disease Control and Prevention (CDC) issued an alert after noticing an increase in the number of S aureus infections in children with flu. The CDC said that from October 2006 through early May, 55 influenza deaths in children had been reported. Twenty of the children (out of 51 for whom relevant data were available) had bacterial infections, and 16 of these were infected with S aureus.

Though the number of pediatric flu deaths this past flu season was similar to the two previous years, the CDC said the 16 deaths from S aureus pneumonia or bacteremia recorded so far reflected a sharp increase over those years. Only one S aureus coinfection was identified during the 2004-05 season, followed by three in 2005-06.

Further, of the 16 children who had S aureus infections, 11 had methicillin-resistant (MRSA) strains that are typically associated with MRSA skin infection outbreaks, the CDC advisory said.

The CDC also noted that the children who had S aureus infections had been in good health before they got sick, but progressed rapidly to serious illness.

Anthony Fiore, MD, a medical epidemiologist with the CDC, told CIDRAP News that because childhood flu deaths have been nationally notifiable only since 2004, it's difficult to make definitive statements about pneumonia death patterns. "It is concerning, and there is a surge in awareness, particularly with the antibiotic resistant strains of Staphylococcus," he said.

The CDC has other ways to track pneumonia trends in children with influenza, he said. For example, the Emerging Infections Program and the New Vaccine Surveillance Network are two systems that can capture clusters of severe infections in children that lead to hospitalization.

Edward Septimus, MD, an infectious disease expert who is medical director of clinical integration at Methodist Hospital in Houston, told CIDRAP News that the clinical picture of the Australian cases possibly suggests a Group A Streptococcus organism. "It's a severe clinical picture and it can act a lot like MRSA. The necrotizing effects are very similar," he said. Jim Henson, the creator of the Muppets, died of a Group A streptococcal pneumonia, Septimus added.

He said that without more information, it's difficult to predict whether the Australian cases point to any troubling trends. Sometimes, he commented, patients are simply unlucky: Their risk of developing a serious pneumonia rises if they are colonized with a bacterial organism such as MRSA or Streptococcus when influenza viruses are circulating.

See also:

Western Australia Department of Health news release
http://www.health.wa.gov.au/press/view_press.cfm?id=711

May 9 CDC health advisory

CDC. Severe methicillin-resistant Staphylococcus aureus community-acquired pneumonia associated with influenza—Louisiana and Georgia, December 2006-January 2007. MMWR 2007;56(14):325-29 [Full text]

Hageman JC, Uyeki TM, Francis JS, et al. Severe community-acquired pneumonia due to Staphyococcus aureus, 2003-04 influenza season. Emerg Infect Dis 2006 Jun;12(6):894-99 [Full text]

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