Chapter 13: Viruses - Types of Animal Infections

Question 1

Host defense plays a major role in the outcome of viral infection. It protects against otherwise lethal infection. Thus, most healthy humand carry a number of? (2)

Answer 1

viruses and antibodies to viruses

Question 2

What happens if a virus is transferred from the immune host of another individual?

Answer 2

• can result in infection

Question 3

What are the categories of animal virus infection? (4)

Answer 3

• acute infection
• persistent viral infection
• Chronic viral infection
• Latent viral infection

Question 4

What are acute infections? (4)

Answer 4

• usually short duration
• disease symptoms result from tissue damage
• lysis of host cells release and spread virus particles
• host defense systems gradually eliminate virus (days or weeks)

Question 5

What does the host acquire from acute infections?

Answer 5

• long lasting immunity
  ex. mumps, polio

Question 6

After acute period, some non-infectious particles remain, which can cause serious disease later in life. What does Measles turn into, and what is fetal brain disorder?

Answer 6

• subacute sclerosing panencephalitis
• FBD occur up to ten years after recovery from measles

Question 7

What is persistent viral infections?

Answer 7

• virus is continuously present in the body, but may or may not cause disease
  ex. no symptoms

Question 8

In persistent viral infections, can viruses still be transmitted?

Answer 8

• yes, as the infected host can still serve as a reservoir

Question 9

What are two types of persistent viral infections? (2)

Answer 9

• Chronic viral infection
• Latent viral infection

Question 10

What is the chronic viral infection? (2)

Answer 10

• after the acute period, infectious virus remains present at all times
• may or may not cause noticeable symptoms
  ex. Hep B

Question 11

How is Hepatitis B an example of a chronic viral infection? (4)

Answer 11

• transmitted by blood or sexually transmitted
• may have acute period (nausea, jaundice, fever)
• after acute period, virus numbers stay high for the rest of the patient’s life
• may cause cirrhosis or liver cancer after years

Question 12

What are latent viral infections? (4)

Answer 12

• acute infection followed by symptomless period (note that this is a type persistent/chronic)
• The virus integrates a copy of its DNA into a host cell xme and remains dormant
  ex. provirus!!!
• disease can be reactivated years later but symptoms can differ

Question 13

Varicella-Zoster virus is an example of a latent viral infection. What is it? (3)

Answer 13

• causes chicken pox in children
• remains latent for years - no disease
• can be reactivated later to cause shingles