Coxsackievirus type A and coxsackievirus type B are members of the Picornaviridae family. Coxsackievirus type A is associated with herpangina,which is commonly seen in children. Herpangina is a severe febrile pharyngitis characterized by vesicles or nodules primarily on the soft palate. The majority of cervical cancers (approximately 90%) contain human papilloma virus DNA, usually of type 16 or 18.

Hepatitis B virus (HBV) is a human carcinogen associated with hepatocellular carcinoma. The incidence of hepatocellular carcinoma is higher in a person who becomes infected with HBV earlier in life. Herpes simplex virus type 1 (HSV-1) is a member of the Herpes viridae family and consists of a double stranded DNA genome. Primary infection with HSV-1 mostly involves the mouth and/or throat. Gingivostomatitis is a classic clinical presentation of HSV-1 infection. Variola virus is a brick-shaped virus with a single linear molecule of double stranded DNA and is a member of the Poxviridae family. Variola virus was the causative agent of smallpox that multiplied in the lymph nodes.

All of the families mentioned are RNA viruses. The Picornaviridae family contains viruses that lack an envelope and are icosahedral (rather than helical) in morphology. The Picornaviridae family contains enterovirus, cardiovirus, and rhinovirus. The Orthomyxoviridae family contains the influenza virus, while the Paramyxoviridae family contains the parainfluenza virus. The Rhabdoviridae and Coronaviridae families contain the rabies virus and Coronaviruses, respectively.

The child has the characteristic symptoms of laryngotracheobronchitis, commonly known as croup.

All of the listed viruses can cause respiratory tract infections in infants and young children, each producing different clinical manifestations. Parainfluenzavirus is the most common agent of croup. Types 1 and 2 are particularly associated with this disease. Croup is characterized by respiratory obstruction due to swelling of the larynx and related structures. Infection may spread deeper to the lower trachea and bronchi, culminating in pneumonia and bronchitis. The infection is seen mostly in 6- to 18-month-old children.  

Respiratory syncytial virus is mostly associated with bronchiolitis and pneumonia. Influenza virus is also one of the agents of laryngotracheitis in infants, though not as frequently as the parainfluenza viruses. The virus can be responsible for pneumonia in infants. Adenoviruses cause common cold-like symptoms and upper respiratory tract infection. Certain serotypes, particularly types 3, 7 and 21, cause pneumonia in children. Mortality rates are higher in the very young. Rhinoviruses are agents of common cold.

Antigenic shift and antigenic drift can be found in the influenza virus.  Antigenic shift is a process by which 2 or more different types of influenza A combine to form a virus radically different from the ancestor strains. Antigenic shift occurs in 2 ways.

1. Antigenic shift can occur through genetic recombination, or reassortment, when 2 or more different influenza A viruses infect the same host cell and combine their genetic material.
2. Qn influenza A virus can jump from 1 type of organism, usually a bird, to another type of organism, such as a human, without undergoing major genetic change.

A point mutation that leads to an amino acid change and altered antigenic sites so that the virus is no longer recognized by the host immune system is called antigenic drift. Peptidoglycan and teichoic acids are components of the bacterial cell wall and prions are infectious protein particles.

Hepatitis E virus is a naked (+) strand, ssRNA virus. It has clinical and biochemical features that are very similar to Hepatitis A, except that it seems to be more severe in pregnant women. Therefore, Hepatitis E is the virus that is most likely the cause of disease in this case, if serology indicated the absence of Hepatitis A.

The other choices are incorrect. Hepatitis C is enveloped and does not cause gastrointestinal symptoms. Rhinovirus causes common cold. Rotavirus does not present with jaundice as do hepatitis-causing viruses. Last, yellow fever can be associated with hepatitis, but it is a lot more severe in presentation than Hepatitis A and is transmitted by mosquitoes, not fecal-orally.

Genital tract infections by human papilloma viruses is considered a sexually transmitted disease. HPV type 6 and 11 are mostly implicated in genital warts that are found on the squamous epithelium of the external genitalia and perianal areas. Intraepithelial neoplasia and carcinoma often result from genital tract infections caused by HPV type 16 and 18. Herpes simplex virus type 2 is a major cause of genital herpes, which is another sexually transmitted disease. Primary infection is accompanied by inguinal adenitis, fever, malaise, myalgia, and lesions on genital areas.

 On the other hand, the other choices are incorrect. Viral infection of the heart and cardiac muscles can be presented as myocarditis, pericarditis, or cardiomyopathy, which can cause subsequent damage. Coxsackie B virus and echovirus are associated with myocarditis and pericarditis in newborns, children, and adults characterized by recrudescence, leading to permanent heart damage, cardiomegaly, or congestive heart failure. Coxsackie virus type B and echovirus 11 can infect newborns prenatally, natally, or postnatally, resulting in the encephalomyocarditis syndrome. Viral hemorrhagic fevers are characterized by a widespread hemorrhage from the body's epithelial surface, which includes the internal mucosa (such as gastrointestinal tract). The virus infects the endothelial cell lining of the vasculature and may cause cytolysis that results in increased permeability or rupture of the vessel. Thrombocytopenia, leukopenia, petechiae, and ecchymoses are some of the common presentation. Yellow fever and Dengue shock syndrome can result in death within hours due to hypovolemic shock. Respiratory syncytial virus (RSV), Influenza virus, and parainfluenza 3 viruses are common causes of acute bronchitis. RSV and parainfluenza 3 virus infections in infants younger than 6 months can result in life threatening pneumonia or bronchiolitis. Influenza is a major cause of respiratory infection in the general population. Influenza virus targets and destroys mucus-secreting epithelial cells, leading to the loss of primary defense system. New strains emerge every year and can effect a large population, including the children who are universally susceptible to new strains. Last, viral infections of the gastrointestinal tract with rotavirus and Norwalk virus can lead to gastroenteritis and diarrhea. These viruses infect the small intestine and damage the epithelial lining and absorptive villi, which can lead to malabsorption with water and electrolyte imbalance. Rotaviruses are a major cause of infantile gastroenteritis, which can cause extensive tissue damage leading to serious fluid and electrolyte loss. Norwalk virus is associated with gastroenteritis in younger children and adults.

The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells.

On the other hand, negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

The inclusion bodies are the stainable structures found within the nucleus or cytoplasm of the host cell. Inclusion bodies result from the histological changes caused by the presence of viral components or the changes in the cell structure mediated by the infecting virus. The detection of the inclusion bodies by microscopic examination can be used for laboratory diagnosis of the viral infection, as they are characteristic for particular viral infections. Cowdry Type A inclusions are intranuclear inclusion bodies characteristic of infection with varicella zoster virus (VZV) or herpes simplex virus (HSV). These inclusions can be found in single cells or in large syncytia. Examination of the HSV infected cells in tissues or smear reveals giant cells with characteristic intranuclear inclusions that are acidophilic and are known as Cowdry Type A inclusions. Cowdry Type A inclusions are also seen in skin lesions, respiratory specimens, or organ biopsies in the cytological examination of cells infected with VZV.

On the other hand, negri bodies are acidophilic inclusions found in the cytoplasm in brain tissue and are characteristic of infection with the rabies virus. Owl's eye-intranuclear inclusions are characteristic of cytomegalovirus infection. These are large basophilic inclusion bodies detected in cells of tissues or urine sediment stained for cytological examination. Guarnieri bodies are inclusion bodies, associated with infection with the pox virus. The scraping of cells from the lesion is stained and examined microscopically. Guarnieri bodies appear as acidophilic inclusions in the cytoplasm of infected cells. Perinuclear inclusion bodies in the cytoplasm are associated with reovirus infection. When the infected cells are observed for cytopathic effect, the inclusions appear as small dots in the periphery of the host cell cytoplasm early in the infectious cycle. Larger acidophilic inclusions located adjacent to the nucleus are detected later in the infectious cycle.

Adenoviruses are non-enveloped viruses with an icosahedral nucleocapsid. The capsid contains 12 pentons at each vertices with 12 fibers projecting from the vertices. The genome is a linear double stranded DNA with terminal protein. Viral attachment proteins are present in the fibers projecting from the vertices of the virions.

The additional characteristics of adenovirus include the following:

• The virions replicate in the nucleus
• Encode proteins to promote mRNA and DNA synthesis, including its own DNA polymerase
• Infects epithelial cells lining respiratory and enteric organs
• Virus can become latent in lymphoid tissue and can be reactivated by immunosuppression or infection with other agents
• Forms basophilic intranuclear inclusions within an infected epithelial cell

Last, they are commonly associated with respiratory diseases, adenoviral pneumonia, epidemic keratoconjunctivitis, and pharyngoconjunctival fever.

JC virus is a papovavirus associated with progressive multifocal leukoencephalopathy (PML) in immunocompromised patients, including AIDS. PML is a subacute demyelinating disease of the central nervous system, which is primarily seen as a complication of advanced disseminated malignant conditions (such as Hodgkin's disease or chronic lymphocytic leukemia). The patient presents with multiple neurological symptoms; the symptoms are not attributable to a single anatomical lesion. Clinical manifestations include impairment of vision, speech, and coordination that can lead to paralysis and death.

On the other hand, laryngotracheobronchitis, commonly known as croup, is one of the serious manifestations of parainfluenza virus infection in infants and young children. Parainfluenza type 1 is a common cause of croup that results in subglottal swelling and airway obstruction. Major clinical manifestations include hoarseness, "barking" cough, tachypnea, tachycardia, and suprasternal retraction. A cold sore is a recurrent mucocutaneous infection caused by herpes simplex virus (HSV). The individual retains HSV-1 DNA in the trigeminal ganglion for life following recovery from primary oropharyngeal HSV infection. Cold sores, also known as herpetic labialis, are manifested as a result of activation of HSV from the trigeminal ganglia. Cold sores are characterized by development of a cluster of vesicles around the mucocutaneous junction of the lips. Lassa fever virus is an Arenavirus associated with hemorrhagic fever. Lassa fever virus is enzootic in the West African peridomestic rodent. The rodent transmits the virus to the human by contaminating the house with urine. The infection is characterized by fever, headache, malaise, coagulopathy, petechiae, vomiting, pharyngitis, and occasional visceral hemorrhage. Serious manifestations include carditis, hepatitis, encephalopathy, pneumonitis, conjunctivitis, etc. Cardiovascular collapse results in death in 20% of the hospitalized cases. Hand, foot, and mouth disease is a vesicular exanthem caused by coxsackievirus A16. It is characterized by ulcerating vesicles on hand, foot, mouth, and tongue along with mild fever.