Current research on respiratory viral infections: Fifth International Symposium

The cell biology of acute childhood respiratory disease: therapeutic implications

Respiratory syncytial virus (RSV), the recently identified human metapneumovirus (HMPV), and the human parainfluenza viruses (HPIVs), cause most cases of childhood croup, bronchiolitis, and pneumonia. Influenza virus also causes a significant burden of disease in young children, although its significance in children was not fully recognized until recently. This article discusses pathogens that have been studied for several decades, including RSV and HPIVs, and also explores the newly identified viral pathogens HMPV and human coronavirus NL63. The escalating rate of emergence of new infectious agents, fortunately meeting with equally rapid advancements in molecular methods of surveillance and pathogen discovery, means that new organisms will soon be added to the list. A section on therapies for bronchiolitis addresses the final common pathways that can result from infection with diverse pathogens, highlighting the mechanisms that may be amenable to therapeutic approaches. The article concludes with a discussion of the overarching impact of new diagnostic strategies.

VACCINATIONS | Viral

Vaccines are preparations of weakened or killed viruses or viral subunits that trigger specific protective immunity. Vaccination is the single most effective tool for preventing communicable disease, highlighted by the achievements of the smallpox and poliomyelitis eradication programs and the rise in infections for which no effective vaccine is available: human immunodeficiency virus, malaria, worms, and tuberculosis. World Health Organization initiatives target acute respiratory diseases in infancy and early childhood with novel immunization approaches.

Effective vaccines are needed urgently for viral respiratory diseases, but progress has been disappointingly slow. Vaccine candidates often show reduced efficacy in infancy, in partially immune adults, the immunocompromised, and the elderly. However, several promising vaccines are in clinical trial, and it is likely that vaccines against respiratory syncytial virus and parainfluenza will be licensed within the next 5–10 years. Mucosally delivered influenza vaccine is now available, and novel adjuvants offer the prospect of better immunogenicity. Ideally, multivalent mucosal vaccines will be developed that provide protection against a spectrum of respiratory infections in specific target age groups.

UPPER RESPIRATORY TRACT INFECTION

Upper respiratory tract infection (URI) is a general term for a heterogeneous group of illnesses caused by numerous etiologic agents that affect the mucosal lining of the upper respiratory tract, including the middle-ear cavity and paranasal sinuses. URIs are primarily caused by viruses, rhinoviruses being the most common etiological agents. Respiratory viruses transmit easily via direct contact or aerosols. The incidence of URI is highest in children who suffer 6–8 infections per year. The main symptoms of URI are nasal blockage and discharge, sneezing, sore throat, and cough. Fever occurs variably, most commonly in children. Viral URIs often predispose to bacterial complications. Acute otitis media is the most common complication in children, whereas sinusitis and pneumonia are more frequent in adults and the elderly. The treatment of URI is mainly symptomatic because specific antivirals are available only for influenza viruses. Antibiotics have no efficacy for viral URI but are commonly used for treating acute otitis media and sinusitis. Most URIs are self-limited illnesses with an average duration of 7–10 days and an excellent prognosis.