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Human Immunodeficiency Virus

The epidemiology, prevention, diagnosis, clinical manifestations, infectious complications, and management of HIV are covered in Chapter 109, Chapter 110, Chapter 111, Chapter 112, Chapter 113 . HIV types 1 and 2 (HIV-1 and HIV-2) are members of the Lentivirus genus of the Retroviridae family. HIV-1 and HIV-2 appear to have entered humans as a result of cross-species transmission of simian immunodeficiency viruses (SIVs). HIV-1 is similar…

Human T-Cell Lymphotropic Viruses

Epidemiology Human T-cell lymphotropic viruses (HTLV) include four types (HTLV-1, HTLV-2, HTLV-3, and HTLV-4). HTLV-1 and HTLV-2 were first reported in 1980 and 1982, respectively, and are the two most clinically important HTLVs. , Infections with HTLV-3 and HTLV-4 were identified in Cameroon in 2005, although the prevalence, transmissibility between humans, and clinical significance are not well defined. , There is significant geographic variation in the…

Filoviruses and Arenaviruses

Description of the Pathogens Viruses of the families Filoviridae and Arenaviridae are composed of single-stranded RNA in lipid envelopes. The Filoviridae family of viruses is further divided into three genera: Ebolavirus , Marburgvirus , and Cuevavirus . Within the genus Ebolavirus , six viruses have been identified : Ebola virus (species Zaire ebolavirus ), Sudan virus (species Sudan ebolavirus ), Taï Forest virus (species Taï Forest…

Influenza Viruses

Acknowldgment The authors acknowledge substantial contributions to this chapter from work of Joseph Bresee in previous editions. Influenza viruses cause annual winter epidemics of respiratory illness in temperate climates and have resulted in four influenza pandemics since 1900. The global burden of influenza and global variation in influenza virus circulation patterns are increasingly recognized. In the US, influenza is estimated to result in 12,000–61,000 deaths and…

Rabies Virus

The Virus Rabies virus and 17 bat lyssaviruses are members of the Rhabdoviridae family, genus Lyssavirus, which is derived from the Greek word lyssa, meaning “madness.” Rabies derives from the Sanskrit word rabhas, which means “to do violence.” Rabies virus and many lyssaviruses cause human encephalitis through zoonotic infection. The lyssaviruses differ antigenically but are morphologically similar and neurotropic. Rabies virus is an enveloped, bullet-shaped virus…

Rubeola Virus: Measles and Subacute Sclerosing Panencephalitis

Rubeola (i.e., measles) is an acute, highly contagious, vaccine-preventable viral infection. , In the prevaccination era, measles was an almost universal experience during childhood. The incidence of measles declined markedly in the US after the licensure of a live measles vaccine in 1963. In 2000 the US declared elimination of endemic measles (i.e., absence of sustained virus transmission for >12 months) due to high rates of…

Human Metapneumovirus

Description of Pathogen Human metapneumovirus (HMPV, MPV) was first described in 2001 by Dutch investigators who collected a number of unidentified virus isolates over a 20-year period. Electron micrograph and biochemical studies of the virus showed that it was pleomorphic with a lipid envelope ( Fig. 226.1 ). Reverse transcription-polymerase chain reaction (RT-PCR) and sequence analysis of the virus genome identified it as a pneumovirus, formerly…

Respiratory Syncytial Virus

Lower respiratory tract disease caused by respiratory syncytial virus (RSV) in the US and other industrialized countries results in hospital admission for approximately 2% of all children in the first 12 months of life. By 2 years of age, most children have been infected at least once by RSV, making this infection one of the most common diseases of childhood. Most RSV infections among otherwise healthy…

Mumps Virus

Mumps (i.e., epidemic parotitis) is an acute, vaccine-preventable disease of childhood that typically involves swelling of one or both parotid glands, although many different organs can be infected. Childhood mumps has become uncommon in the US since the widespread implementation of measles-mumps-rubella (MMR) vaccination. Reports of mumps outbreaks involving highly vaccinated populations in the US and other countries have prompted re-evaluation of current mumps vaccination strategies.…

Parainfluenza Viruses

Parainfluenza viruses (PIVs) were first identified in humans in the late 1950s. Human PIVs (PIVs) were initially described in children with croup and subsequently recognized as an important cause of acute respiratory tract infections in patients who are immunocompromised, have chronic conditions, or are elderly. In otherwise healthy children, PIVs cause upper and also lower respiratory tract infections (URIs and LRIs, respectively) such as pneumonia, bronchiolitis,…

Human Coronaviruses

Overview of the Viruses Coronaviruses are included in the Coronaviridae family under the order Nidovirales. They are enveloped, non-segmented, single-stranded, positive-sense RNA viruses named after their corona-like or crown-like surface projections seen on electron microscopy that correspond to large surface spike proteins ( Figs. 222.1 and 222.2 ). Four genera of coronaviruses have been described. Coronaviruses are host-specific and can infect humans and a variety of…

Rubella Virus

Rubella (i.e., German measles) is a benign, self-limited, vaccine-preventable viral illness. Acquired rubella is characterized by an exanthem and lymphadenopathy, although infants and children with rubella frequently are asymptomatic. Much of the morbidity attributed to rubella virus (RuV) occurs from in utero transmission, especially during the first trimester, resulting in miscarriage, stillbirth, fetal death, or congenital rubella syndrome (CRS). Sequelae of CRS include growth retardation, deafness,…

Hepatitis C Virus

Hepatitis C virus (HCV) was first identified in 1989. Although substantially more prevalent among adults, HCV infection does occur in children and should be considered when relevant clinical or epidemiologic factors are present. , In recent years, new HCV infections have increased among women of childbearing age and the number of infants born to HCV-infected mothers has risen, resulting in vertically transmitted infections. , Curative treatment…

Bunyaviruses

Description of Pathogen The family Bunyaviridae was recently reclassified, with Bunyavirales becoming an order and several new family names being designated. , However, the genera that have important human pathogens have remained relatively unchanged and include Orthohantavirus, Orthonairovirus, Bandavirus, Phlebovirus , and Orthobunyavirus. A wide range of clinical syndromes in humans exist among the pathogenic bunyaviruses, with the severity of human infections ranging from mild febrile…

Flaviviruses

The flaviviruses are single-stranded, enveloped RNA viruses that are transmitted to humans primarily through the bites of arthropods. Although >40 arthropod-borne flaviviruses have been described, this chapter discusses those that are most important in causing human illness: yellow fever virus (YFV), dengue viruses, Japanese encephalitis virus (JEV), West Nile virus (WNV), tickborne encephalitis virus (TBEV), and Zika virus (ZIKV). Other flaviviruses not discussed in this chapter…

Togaviridae: Alphaviruses

Alphaviruses are arthropod-borne members of the family Togaviridae. They are small, enveloped, positive-sense RNA viruses. , Members of the western equine encephalitis, eastern equine encephalitis, and Venezuelan equine encephalitis serocomplexes cause encephalitis in equines and humans. Members of the Semliki Forest serocomplex, such as chikungunya, o’nyong-nyong, Mayaro, and Ross River viruses, cause epidemic fever and arthralgia. Epidemiology and Clinical Manifestations Chikungunya Virus Chikungunya virus is transmitted…

Rotaviruses

Before the availability of rotavirus vaccines, rotaviruses were the most common cause of severe infant and childhood gastroenteritis worldwide, responsible for 40% of all diarrheal hospitalizations and more than half a million deaths among children aged <5 years annually. To mitigate this substantial disease burden, rotavirus vaccines were developed and are now licensed in many countries. By 2020, 103 countries had introduced rotavirus vaccines in their…

Coltivirus (Colorado Tick Fever)

Colorado tick fever (CTF) is an acute febrile illness caused by CTF virus, a double-stranded RNA virus in the Coltivirus genus of the family Reoviridae ( Box 215.1 ). , The virus is transmitted to humans through the bite of an infected Rocky Mountain wood tick, Dermacentor andersoni ( Fig. 215.1 ). BOX 215.1 Colorado Tick Fever: Agent and Epidemiology Agent Colorado tick fever virus, Coltivirus…

Human Parvoviruses (Parvovirus B19 and Bocavirus)

Parvoviruses—small (20–25 nm), nonenveloped, icosahedral, single-stranded DNA viruses with a linear genome of between 4500 and 5600 nucleotides—are common infectious agents of animals, including birds and insects, as well as humans. At least five different genera of parvovirus have been detected in humans: bocaparvoviruses, dependoparvoviruses, erythroparvoviruses, protoparvoviruses, and tetraparvoviruses. Human bocavirus (HBoV) has been identified in respiratory secretions of young children with acute wheezing and lower…