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.

CCR5 is necessary for HIV entry into the host cell. CCR5 is expressed by macrophages, dendritic cells, and CD4 T cells. It is thought to be the major co-receptor for establishing primary infection, since individuals who are homozygous for a mutation in CCR5 appear to be resistant to infection by HIV. For example, the CCR5-Delta32 deletion mutation seems to confer resistance against HIV-1 by blocking its attachment to CCR5 so that HIV cannot gain entry to the cell. Development of drugs directed at chemokine receptors is thus an active area of research.

On the other hand, CXCR4 is the other major co-receptor for HIV. Lymphotropic HIV uses CXCR4 found on T cells and requires a high density of CD4 on the cell surface. CXCR4 also binds the CXC-chemokine stromal-derived factor-1 (SDF-1) as a co-receptor. Both co-receptors are G-coupled proteins with 7 transmembrane spanning domains. Mac-1, also called CD11b/CD18, is stored in specific granules that are shuttled to the granulocyte surface. It exists as a chemoattractant activation-dependent molecule that undergoes a conformational change upon stimulation. Until stimulation occurs, it remains in a resting, non-adhesive state. Mac-1 is a β2 integrin. SDF-1 is a small chemokine of the CXC subfamily that is produced constitutively by bone marrow stromal cells and has an important role in early stages of B cell development. It is a growth factor for B cell progenitors and a chemotactic factor for T cells, monocytes, CD34+ hematopoietic progenitor cells, mature megakaryocytes, and dendritic cells. Interleukin-8 or IL-8, a CXC chemokine, is an 11-kDa homodimer of 99 amino acids that is also known as monocyte-derived neutrophil chemotactic factor (MDNCF). It is an important mediator of neutrophil, lymphocyte, and basophil chemotaxis and activation. It is released from several cell types in response to an inflammatory response.

The flu virus can be either live attenuated or inactivated. The center for disease control and prevention (CDC) recommends giving the flu virus annually to healthy adults, pregnant women, and children older than 6 months of age. The virus is different from year to year, and the vaccine each year represents the most common active forms of the virus. Vaccination is a type of primary prevention.

Viral replication takes place in several stages. Once the virus recognizes the target cell, it binds to the cell. The viral attachment protein present on the surface of virion interacts with the cell receptor. Following attachment the virus can penetrate the cell by process of endocytosis or fusion. In the step of uncoating the capsid the envelope is removed and viral nucleic acid is released inside the host cell, so the viral genes become available for transcription.

In the protein synthesis step the process differs according to type of virus and the structure of genome. RNA virus mostly replicates in the cytoplasm. Plus-strand RNA viruses initiate protein synthesis. Minus-strand RNA virus, double-stranded RNA viruses, and DNA viruses initiate nucleic acid synthesis. Protein synthesis in DNA virus replication is divided into early phase and late phase. Once the replication is over the newly synthesized viral protein and nucleic acid is assembled inside the cells. The capsomers are self assembled into capsid. In enveloped virus the viral envelope is added from the cell membrane and becomes associated with nucleocapsid. The newly assembled virus is released from the cell by budding or cell lysis.

Aspergillus flavus is a mold species commonly found in peanut butter and many other foods. It produces aflatoxin, a toxin linked to increased risk of liver cell cancer. The other mold species listed are not considered to be related to liver cancer. Cladosporium species are rarely harmful to humans. Penicillium species produce antibiotics, which we commonly use to treat infections. Mucor species cannot grow in warm temperatures, and are unable to infect humans, with the exception of certain heat-tolerant strains, which may cause some zygomycosis.