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Arboviral Infections

The arthropod-borne viral infections are a group of mosquito- or tick-transmitted pathogens of several taxa manifested clinically mostly as neurologic infections, influenza-like illnesses, or acute viral exanthems. In temperate countries, arboviruses are transmitted during warmer weather; however, in tropical and subtropical countries, arboviruses may be transmitted year around either in an urban cycle (human to mosquito to human) or by arthropods that feed on other vertebrate…

Human Papillomaviruses

See also Chapter 687 . Human papillomaviruses (HPVs) cause a variety of proliferative cutaneous and mucosal lesions, including common skin warts, benign and malignant anogenital tract lesions, oral pharyngeal cancers, and life-threatening respiratory papillomas. Most HPV-related infections in children and adolescents are benign (see also Chapter 687 ). Etiology The papillomaviruses are small (55 nm), DNA-containing viruses that are ubiquitous in nature, infecting most mammalian and many…

Rotaviruses, Caliciviruses, and Astroviruses

Diarrhea is a leading cause of childhood death in the world, accounting for 5-10 million deaths per year. In early childhood, the single most important cause of severe dehydrating diarrhea is rotavirus infection. Rotavirus and other gastroenteric viruses are not only major causes of pediatric deaths but also lead to significant morbidity. Children in the United States, before vaccine was available, were estimated to have a…

Coronaviruses

Coronaviruses are increasingly recognized as important human pathogens. They cause up to 15% of common colds and have been implicated in more serious diseases, including croup, asthma exacerbations, bronchiolitis, and pneumonia. Evidence also suggests that coronaviruses may cause enteritis or colitis in neonates and infants and may be underappreciated as agents of meningitis or encephalitis. Four coronaviruses are endemic in humans: human coronaviruses (HCoVs) 229E, OC43,…

Rhinoviruses

Human rhinoviruses (HRVs) are the most frequent cause of the common cold in both adults and children. Although HRVs were once thought to cause only the common cold, it is now known that they are also associated with lower respiratory infections in adults and children. Many HRVs do not grow in culture. Recent studies using molecular diagnostic tools such as the polymerase chain reaction (PCR) have…

Adenoviruses

Human adenoviruses (HAdVs) are a common cause of human disease. Conjunctivitis is a familiar illness associated with the HAdVs, but these viruses also cause upper and lower respiratory disease, pharyngitis, gastroenteritis, and hemorrhagic cystitis. HAdVs can cause severe disease in immunocompromised hosts. Outbreaks of HAdV infection occur in communities and closed populations, notably the military. No currently approved antiviral drugs are highly effective against HAdVs. Vaccines…

Human Metapneumovirus

Etiology Human metapneumovirus (HMPV) is a respiratory virus that has emerged as one of the most common causes of serious lower respiratory tract illness in children throughout the world. Etiology HMPV is an enveloped, single-stranded, nonsegmented, negative-sense RNA genome of the family Pneumoviridae, which comprises large enveloped negative-sense RNA viruses. This taxon was formerly a subfamily within the Paramyxoviridae, but was reclassified in 2016 as a…

Respiratory Syncytial Virus

Respiratory syncytial virus (RSV) is the major cause of bronchiolitis (see Chapter 418 ) and viral pneumonia in children younger than 1 yr of age and is the most important respiratory tract pathogen of early childhood. Etiology RSV is an enveloped RNA virus with a single-stranded negative-sense genome that replicates entirely in the cytoplasm of infected cells and matures by budding from the apical surface of the…

Parainfluenza Viruses

Human parainfluenza viruses (HPIVs) are common causes of acute respiratory illness in infants and children and are important causes of lower respiratory tract disease in young children and immunocompromised persons. These viruses cause a spectrum of upper and lower respiratory tract illnesses but are particularly associated with croup (laryngotracheitis or laryngotracheobronchitis), bronchiolitis , and pneumonia . Etiology HPIVs are members of the Paramyxoviridae family. Four HPIVs…

Influenza Viruses

Influenza viral infections cause a broad array of respiratory illnesses that are responsible for significant morbidity and mortality in children during seasonal epidemics . Influenza A viruses also have the potential to cause global pandemics , which can happen when a new (novel) influenza A virus emerges and transmits efficiently from person to person. Etiology Influenza viruses are large, single-stranded RNA viruses belonging to the family…

Human Herpesvirus 8

Human herpesvirus 8 (HHV-8) is an oncogenic virus identified in tissue specimens from patients with Kaposi sarcoma (KS). Because of this association, it is also known as Kaposi sarcoma–associated herpesvirus . HHV-8 is the etiologic agent of two additional lymphoproliferative disorders: primary effusion–based lymphoma (PEL) and multicentric Castleman disease (MCD) . Etiology HHV-8 is a γ 2 -human herpesvirus similar to Epstein-Barr virus. The virus contains…

Roseola (Human Herpesviruses 6 and 7)

Human herpesvirus 6 (HHV-6A and HHV-6B) and human herpesvirus 7 (HHV-7) cause ubiquitous infection in infancy and early childhood. HHV-6B is responsible for the majority of cases of roseola infantum ( exanthem subitum or sixth disease ) and is associated with other diseases, including encephalitis, especially in immunocompromised hosts. A small percentage of children with roseola have primary infection with HHV-7. Etiology HHV-6A, HHV-6B, and HHV-7…

Cytomegalovirus

Human cytomegalovirus (CMV) is ubiquitous in the population, and individuals who become infected remain persistently infected for life, with intermittent shedding of infectious virus from mucosal surfaces. Although CMV rarely causes symptoms in normal individuals, it is an important cause of morbidity and sometimes death in immunocompromised hosts. CMV remains a well-recognized cause of disease in the newborn infant following intrauterine infection (congenital CMV) and the…

Epstein-Barr Virus

Infectious mononucleosis is the best-known clinical syndrome caused by Epstein-Barr virus (EBV). It is characterized by systemic somatic complaints consisting primarily of fatigue, malaise, fever, sore throat, and generalized lymphadenopathy. Originally described as glandular fever, it derives its name from the mononuclear lymphocytosis with atypical-appearing lymphocytes that accompany the illness. Etiology EBV is a double-stranded DNA virus that is a member of the gammaherpesviruses and causes…

Varicella-Zoster Virus

Varicella-zoster virus (VZV) causes primary, latent, and reactivation infections. The primary infection is manifested as varicella (chickenpox) and results in establishment of a lifelong latent infection of sensory ganglionic neurons. Reactivation of the latent infection causes herpes zoster (shingles). Although often a mild illness of childhood, varicella can cause substantial morbidity and mortality in otherwise healthy children. Morbidity and mortality are higher in immunocompetent infants, adolescents,…

Herpes Simplex Virus

The 2 closely related herpes simplex viruses (HSVs), HSV type 1 (HSV-1) and HSV type 2 (HSV-2), cause a variety of illnesses, depending on the anatomic site where the infection is initiated, the immune state of the host, and whether the symptoms reflect primary or recurrent infection. Common infections involve the skin, eye, oral cavity, and genital tract. Infections tend to be mild and self-limiting, except…

Parvoviruses

The parvoviruses are small, single-stranded DNA viruses. They are common infectious agents of a variety of animal species, including mammals, birds, and insects. Parvoviruses as a group include a number of important animal pathogens. There are 5 different types of parvoviruses known to infect humans: the dependoviruses, also called adeno-associated viruses (AAV), parvovirus B19 (B19V), human bocaviruses (HBoV), parvovirus 4 (PARV4), and human bufavirus (HBuV). B19V…

Nonpolio Enteroviruses

The genus Enterovirus contains a large number of viruses spread via the gastrointestinal and respiratory routes that produce a broad range of illnesses in patients of all ages. Many of the manifestations predominantly affect infants and young children. Etiology Enteroviruses are nonenveloped, single-stranded, positive-sense viruses in the Picornaviridae (“small RNA virus”) family, which also includes the rhinoviruses, hepatitis A virus, and parechoviruses. The original human enterovirus…

Polioviruses

Etiology The polioviruses are nonenveloped, positive-stranded RNA viruses belonging to the Picornaviridae family, in the genus Enterovirus, species Enterovirus C and consist of 3 antigenically distinct serotypes (types 1, 2, and 3). Polioviruses spread from the intestinal tract to the central nervous system (CNS), where they cause aseptic meningitis and poliomyelitis, or polio. The polioviruses are extremely hardy and can retain infectivity for several days at…

Mumps

Mumps is an acute self-limited infection that was once commonplace but is now uncommon in developed countries because of widespread use of vaccination. It is characterized by fever, bilateral or unilateral parotid swelling and tenderness, and the frequent occurrence of meningoencephalitis and orchitis. Although infrequent in countries with extensive vaccination programs, mumps remains endemic in the rest of the world, warranting continued vaccine protection. Nonetheless, outbreaks…