Jawetz Chapter 30

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Questions and Answers

What is true about clinical illness as an indicator of viral infection?

It is an insensitive indicator of viral infection. (correct)

It is a reliable indicator of all viral infections.

It always presents with noticeable symptoms.

It is a highly sensitive indicator.

What is the role of secretory antibody (IgA) in resistance following viral infection?

Usually important in preventing reinfection. (correct)

Only important during initial exposure.

Not significant in the immune response.

Usually leads to a chronic infection.

Which viral group is commonly associated with respiratory infections?

Paramyxovirus (correct)

Hepadnavirus

Papillomavirus

Calicivirus

What can be true about the duration of immunity following viral infections?

It varies and can be short. Signup and view all the answers

Which of the following viruses is NOT typically transmitted via the mouth or intestinal tract?

Herpes simplex virus Signup and view all the answers

Which type of infection rout includes the use of mild trauma?

Skin infections with poxvirus. Signup and view all the answers

What type of immunity responses do viral infections trigger?

Both innate and adaptive immune responses. Signup and view all the answers

What is often true of inapparent infections by viruses?

They are very common. Signup and view all the answers

Which virus is NOT listed as associated with respiratory infections?

Herpes simplex virus Signup and view all the answers

What primary site is associated with influenza infections?

Nasal and oral mucous membranes Signup and view all the answers

Which virus is primarily associated with intestinal infections?

Rotavirus Signup and view all the answers

In which body part does the rabies virus exhibit no shedding?

Brain Signup and view all the answers

Which of the following is a possible site of replication for hepatitis B?

Liver Signup and view all the answers

What does primary viremia involve in the context of viral infections?

Presence of virus in blood Signup and view all the answers

Which virus is known for shedding from skin?

Varicella Zoster Signup and view all the answers

What is a common mechanism of spread for arboviruses?

Secondary viremia Signup and view all the answers

Which virus is primarily associated with shedding in the lungs?

Influenza Signup and view all the answers

What type of virus is associated with skin infections?

Papillomavirus Signup and view all the answers

Where do mumps virus particles primarily shed?

Salivary glands Signup and view all the answers

What is a way that some viruses can breach the skin barrier?

Through small abrasions in the skin Signup and view all the answers

Which type of viruses are commonly introduced through arthropod bites?

Arboviruses Signup and view all the answers

What is the significance of the blood-brain barrier in viral infections?

It can be breached by neurotropic viruses allowing CNS spread Signup and view all the answers

How can herpesviruses spread within the nervous system?

Via axonal transport to dorsal root ganglia neurons Signup and view all the answers

What is a common method through which hepatitis B virus can be introduced into the body?

By transfusion of contaminated blood Signup and view all the answers

What are the pathways through which viruses can spread to the central nervous system (CNS)?

By peripheral nerves and viremia Signup and view all the answers

Which type of infection is typically subclinical in eastern equine encephalomyelitis (EEE) in certain bird species?

Always subclinical Signup and view all the answers

What type of interaction occurs when a virus is present but not replicating, such as in some cases of human papillomavirus?

Occult infection Signup and view all the answers

Which of the following best describes the infection pattern of measles?

Acute and almost always clinically apparent Signup and view all the answers

What is the reactivation pattern of herpes simplex virus (HSV) after initial childhood infection?

Periodic reactivation throughout life Signup and view all the answers

What characterizes the infection pattern of hepatitis B after recovery from clinical disease?

Associated with chronic infection Signup and view all the answers

Which of the following diseases is known for having a 'slow' infection characterized by long incubation periods?

Scrapie Signup and view all the answers

What is a key feature of lungworm-induced swine flu in pigs?

Remains occult until stimulated Signup and view all the answers

Which viral disease may result in apparent (clinical) and inapparent (subclinical) infections, such as with adenoviruses?

Influenza Signup and view all the answers

What kind of infection may be recognized after a long period of unrecognized presence of the virus?

Slow infection Signup and view all the answers

What type of infection is associated with the Latent stage during which a virus is present in small quantities?

Latent infection Signup and view all the answers

What form of tolerance develops in mice infected with LCM virus in utero?

Virus-specific T cell non-activation Signup and view all the answers

What results from the formation of antigen-antibody complexes in the chronic infection of LCM virus?

Immune complex disease Signup and view all the answers

How can the presence of LCM virus in chronically infected hosts be demonstrated?

By transmission to indicator hosts Signup and view all the answers

What is a common outcome for adult mice infected with LCM virus?

Classic acute symptoms and frequent death Signup and view all the answers

What challenge is posed by the presence of an occult virus during infection?

It may not be replicating detectably Signup and view all the answers

Which virus is the most common cause of the common cold in adults?

Rhinovirus Signup and view all the answers

Which virus is primarily associated with laryngitis or croup in infants?

Parainfluenza virus Signup and view all the answers

What is a key symptom of bronchiolitis in infants caused by respiratory syncytial virus?

Dyspnea Signup and view all the answers

What main symptoms are associated with pneumonia in children?

Cough and chest pain Signup and view all the answers

Which virus is least commonly associated with pneumonia in adults?

Coxsackie virus Signup and view all the answers

Study Notes

Viral Infections Overview

Clinical illness is not a reliable indicator of viral infection; both symptomatic and asymptomatic infections are common.
Viremia varies; it can be absent or present during infections, impacting immune response and recovery.

Duration of Immunity

Immunity duration after viral infection can be variable, often short, but typically lifelong immunity can develop in certain cases.

Recovery from Infection

Secretory antibody (IgA) plays a significant role in resistance to viral infections in most cases, while it is usually not important in inapparent infections.
Post-infection outcomes include the host succumbing, recovering, or developing chronic infections, with mechanisms of recovery involving both innate and adaptive immune responses.

Common Routes of Viral Infection

Respiratory Tract: Common viruses include parvovirus, adenovirus, and influenza virus, leading to both localized symptoms and generalized infections.
Mouth and Intestinal Tract: Adenovirus types 40 and 41, calicivirus, and reovirus are prevalent here, often causing gastrointestinal symptoms.
Skin:
- Mild trauma introduces viruses like papillomavirus and herpesvirus.
- Infections can also occur via injection (e.g., hepatitis B) or bites (e.g., rabies virus).

Mechanisms of Viral Spread

Primary and secondary viremia involves the movement of viruses through blood and can affect organs like the liver, spleen, and eventually the central nervous system.
Pathways for central nervous system (CNS) infection include direct entry via blood or travel along peripheral nerves.

Viral Infections and Disease Presentation

Measles: Typically results in acute clinical illness with long-lasting immunity; can lead to chronic conditions like subacute sclerosing panencephalitis.
Hepatitis B: May lead to chronic infections even after recovery from clinical symptoms.
Human Papillomavirus (HPV): Can result in long-term chronic conditions, with possible progression to cancer.

Notable Viral Diseases by Age Group

Common Cold: Rhinoviruses predominantly affect infants and adults.
Laryngitis/Croup: Mainly caused by parainfluenza viruses across all age groups.
Pneumonia: Respiratory syncytial virus is commonly seen in infants, while adults often experience influenza-related pneumonia.

Viral Skin Infections

The skin's keratinized epithelium acts as a barrier; however, viruses can infect through abrasions, insect bites, or injections.
Neurotropic viruses can breach the blood-brain barrier, often correlating viremia levels with neuroinvasiveness.

Implications for Viral Research

There is interest in “slow” infections that involve long incubation periods, such as scrapie and kuru.
Lymphocytic choriomeningitis (LCM) can present with chronic, occult infections leading to later symptomatic infections upon transmission to naïve hosts.

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Description

Explore the complexities of viral infections, focusing on the insensitivity of clinical illness as an indicator of infection, the presence of viremia, and the variability in the duration of immunity. This quiz will test your understanding of these critical concepts in virology and the nature of inapparent infections.