Influenza A and B Virus Infections in Children

In order to obtain data on the severity of influenza children infection, age distribution and clinical symptoms of the basic situation leading to hospital referral, we conducted a survey on children treated at Turku University Hospital in 1980 (Turku, Finland). Retrospective Studies Among the 15,420 children examined in 1999, 683 patients detected influenza A or B antigens in the nasopharyngeal aspirate. The median age of influenza A children was 0 years (n = 544) and the median age of influenza B children was 2 years (n = 139) (P <0.001). One in four children has a potential illness. High fever, cough, rhinorrhea are the most common symptoms. 24% of children suffer from acute otitis media and 9% suffer from pneumonia. This study showed that the majority of children hospitalized for pediatric influenza had previously involved healthy infants and young children. Confirmation in the influenza laboratory is particularly important for children as the clinical symptoms of infectious diseases are not as good as in adults.

Tri-type A influenza virus infection in a population can not be diagnosed only by clinical signs and symptoms and clinical testing is required. Avian influenza A virus infection is usually diagnosed by collecting swabs from the patient's upper respiratory tract (nose and throat). The sample is sent to the laboratory and the laboratory passes the molecular test to try to propagate the virus or both to discover avian influenza A virus. (Propagation of avian influenza A virus can only be performed in laboratories with high levels of biosafety.)

Influenza infection is caused by members of the virus belonging to the family Orthomyxoviridae (Greek ortho means direct, Greek mucus means mucus). There are three main types of influenza A, influenza B, influenza. Let's consider the influenza A virus here. It is also called avian influenza (Collier et al., 2006). Influenza virus A is classified based on the change in the two proteins found on the surface of the virus. Hemagglutinin is a glycoprotein that exists on the surface of the virus and has rod-like protrusions abbreviated as HA, and there are 16 types. Another type of glycoprotein is neuraminidase, abbreviated as NA, and has nine subtypes, which have the ability to agglutinate erythrocytes and promote attachment and penetration of viruses and cell receptors. About 80% of them are HA and the ratio of HA to NA is about 4-5. The most important subtypes that can cause widespread human outbreaks are the H1N1, H1N2 and H3N2 viruses (Richman et al., 2009).

This genus is influenza B virus. Influenza B virus is almost completely infected with humans and is not as common as influenza A virus. Other only animals known to be infected with influenza B virus are seals and ferrets. Since this type of influenza mutates at a rate 2 to 3 times slower than type A, genetic diversity is low and only one type B serotype is. Due to the lack of diversity of antigens, immunity against influenza B usually comes early. However, mutants of influenza B virus are sufficient to cause persistent immunity. This reduction in antigenicity rate, coupled with its limited host range (suppression of cross-species antigenic change), ensures that no influenza B pandemic will occur