Chapter 14 Entry, exit and transmission

Question 1

What does HPV cause and what layer of the skin is it restricted to?

Answer 1

warts, some may cause cancer, infection restricted to epidermis

Question 2

How many types of hemagglutinins and neuraminidases and how does this lead to antigenic drift?

Answer 2

11 hemagltinnins, 18 neuraminidases. Many possible combinations, mutations, lead to antigenic drift

Question 3

How does reassortment happen in the context of influenza?

Answer 3

if two viruses are simultaneously infecting the cell, the virus particle can pick up chicken or pig hemagglutinin, which leads to antigenic shift and to pandemics every 8-10 years

Question 4

What does the genetic material of influenza virus consist of?

Answer 4

RNA virus with 8 segments of RNA

Question 5

What is the mechanism of Tamiflu?

Answer 5

blocks neuraminidase activity so virus cannot properly exit cell

Question 6

What are the roles of hemagglutinin and neuraminidase in the influenza virus

Answer 6

hemagglutinin is for microbial adhesion, and neuraminidase cleaves sialic acid from cell surface, since the virus binds to sialyloligosaccharides on the host

Question 7

What association is there between the winter and flu season?

Answer 7

Inhaling dry winter air leads to acutely impaired mucociliary function, as well as people congregate in spaces for warmth

Question 8

What two infections notably can be transmitted by urine?

Answer 8

schistosomiasis, typhoid

Question 9

What is the genetic material of SARS coronavirus?

Answer 9

ssRNA

Question 10

Describe the types and routes of vertical transmission.

Answer 10

• prenatal (placenta)
• perinatal (infected birth canal)
• postnatal (milk; direct contact with blood at delivery
• germline (viral DNA sequences in human genome, many ancient retroviruses)

Question 11

What microbial properties aid them in successfully colonizing the GI tract?

Answer 11

• specific attachment to intestinal epithelium
• motility
• production of mucinase
• acid resistance (ex. H. pylori produces urease, which acts on local urea to form a tiny cloud ammonia around the invader, allowing it to tolerate stomach pH)
• bile resistance
• resistance to proteolytic enzymes
• anaerobic growth

Question 12

Where are vertical and horizontal transmission of infections most relevant, respectively?

Answer 12

Most infections are transmitted horizontally, as might be expected in crowded human populations. Vertical transmission becomes more important in small isolated communities.