Influenza viruses in children attending major referral center in Saudi Arabia

Objectives: To determine range of illnesses associated with influenza viruses in children, and antigenic characteristics and similarity between vaccine antigens and influenza strains associated with infections in children attending King Faisal Specialist Hospital and Research Center, Riyadh. Methods: Respiratory specimens consisted of throat swabs, nasopharyngeal aspirates and tracheal aspirates which were prospectively collected from children with fever and respiratory symptoms between October 1997 and June 1998. These specimens were cultured for influenza A and B using primary rhesus monkey kidney cells. Isolates were subtyped using hemagglutination inhibition test (ferret serra). Results: During the 1997 - 1998 season 31 symptomatic children at King Faisal Specialist Hospital and Research Center were confirmed to have influenza virus infections. Of these, 30 (97%) were influenza type A and 1 (3%) was influenza type B. The range of illnesses in these patients included upper respiratory tract infection, laryngotracheitis, bronchopneumonia and sepsis-like illness. Of the 21 influenza A isolates that were subtyped 11 were A(H1N1) and 10 were A(H1N1). The A(H1N1) viruses were antigenically similar to A/Bayern/7/95 and A/Johannesburg/82/96 like component in the 1997-1998 influenza vaccine. One of the A(H3N2) was similar to Al Wuhan/359/95 and A/Nanchung/933/95 like component in the 1997-1998 influenza vaccine, and 10 were similar to A/Sydney/05/97, a related but antigenically distinguished variant of the A(H3N2) component of the 1997-1998 influenza vaccine. The occurrence of A/Sydney/05/97 was associated with increased influenza activity during March and April 1998, and an increase in hospitalized children with this strain. Conclusion: Our data indicates that influenza viruses are important pathogens in our community and are responsible for a variety of respiratory infections in infants and children. The majority of circulating influenza virus types and subtypes during the last influenza season is similar to what has been reported worldwide. This has implications regarding the utilization of influenza vaccine in this region. On the basis of worldwide surveillance data, the vaccine recommended by World Health Organization for the 1998-1999 influenza vaccine contains A/Sydney/5/97 (H3H2)-like. The use of this vaccine in our high-risk children and adolescents should be encouraged.