Viruses

Question 1

Virion

Answer 1

The complete infectious virus particle. All of the components that are needed to infect a new cell and produce new infectious particles.

Question 2

Capsid

Answer 2

A viral protein(s) that form a protective shell or coat that surrounds the viral genetic information. The shape can be helical or icosahedral.

Question 3

Nucleocapsid

Answer 3

A term to describe the viral nucleic acid plus capsid.

Question 4

Lipid envelope

Answer 4

The viral envelope is a lipid bilayer, composed of a membrane from the infected cell, surrounding the capsid of some DNA and RNA viruses.

Question 5

RNA dependent RNA polymerases

Answer 5

RNA copied to RNA

Question 6

DNA dependent DNA polymerases

Answer 6

DNA copied to DNA

Question 7

DNA dependent RNA polymerase

Answer 7

DNA copied into RNA

Question 8

RNA dependent DNA polymerase

Answer 8

RNA copied into DNA

Question 9

Types of capsids

Answer 9

Helical and icosahedral

Question 10

How helical capsid forms

Answer 10

Positive charges on the viral protein interact with the negatively charged phosphate backbone of the viral nucleic acid. The viral proteins interact with each other identically leading to the helical shape of the capsid.

Question 11

How icosehedral capsids form

Answer 11

spherical structures that have the symmetry of an icosahedron but with proteins that are asymmetrical. These proteins (can just be one protein or several) form morphological units (capsomers) that can form capsids with remarkable icosahedral symmetry

Question 12

Negative sense RNA viruses have a __ capsid structure.

Answer 12

helical

Question 13

All DNA viruses have an ___ capsid structure.

Answer 13

Icosahedral

Question 14

Positive vs negative polarity

Answer 14

We talk about polarity only with RNA viruses

A positive polarity means that the genetic material of the virus can be directly translated into protein. It looks like messenger RNA

If an RNA virus has negative polarity (-ssRNA), the viral genome cannot be made into protein until a positive-sense copy of the genome is made. It first needs to be transcribed into messenger RNA before viral proteins can be made.

Question 15

4 RNA virus families with segmented genome

Answer 15

Buyna, Orthomyxo, Arena, Reo

Question 16

Viruses with noninfectious genomes

Answer 16

-ssRNA, retroviruses, dsRNA, and poxviruses all package into their virions polymerases that are necessary for their replication

Question 17

Viruses with infectious genomes

Answer 17

+ssRNA viruses (excluding retroviruses), and DNA viruses (excluding Poxviruses, and hepadnavirus (HBV))

Question 18

Incidence

Answer 18

the number of new cases of infection over a specific period of time

Question 19

Prevalance

Answer 19

the total number of current disease cases, new and old

Question 20

Endemic

Answer 20

the baseline level (prevalence) of disease in a community

Question 21

Epidemic

Answer 21

an increase in the average number of disease seen in a population and is often sudden

Question 22

Basic reproductive number (R0)

Answer 22

the average number of secondary cases occurring from one infected individual in a susceptible population

Question 23

Attack Rate

Answer 23

(the number of new cases among a population during a usually short period) divided by (a population that is at risk (could be the total population)) times 100.

Question 24

Secondary attack rate

Answer 24

the number of contacts that become infected/ total number of contacts

Question 25

Vertical vs horizontal transmission

Answer 25

ertical transmission is spread from the parent to the offspring.

Horizontal transmission is transmitted via person to person.

Question 26

Incubation period

Answer 26

time from infection until symptoms appear

Question 27

Latent period

Answer 27

time from infection until a person becomes infectious

Question 28

Prodromal phase

Answer 28

the generalized symptoms that can occur in many viral infections before specific symptoms arise that might aid in diagnosis

Question 29

Infectious phase

Answer 29

the time that the infected individual can spread the disease to others

Question 30

Iceberg concept of disease

Answer 30

number of asymptomatic or subclinical individuals outnumber the ones who develop symptoms

Question 31

Infectivity

Answer 31

Infectivity is the viruses’ ability to spread or infect individuals.

Question 32

Pathogenecity

Answer 32

Pathogenicity is the extent to which overt disease is present in infected individuals.

Question 33

Virulence

Answer 33

Virulence is the extent of serious clinical disease present in infected individuals.

Question 34

Localized infections

Answer 34

The virus can spread via the epithelial cells of the respiratory system, or intestinal tract BUT does notspread via the bloodstream or lymphatics to different parts of the body

Question 35

Generalized/systemic infections

Answer 35

the virus enters the body but does not extensively replicate at the site of entry. The virus is disseminated to the lymphatic system where, it then travels to the blood (primary viremia). Eventually to target organs

Question 36

Acute infections

Answer 36

Most infections are acute and cleared by the immune system. Some acute infections can lead to lifelong immunity to reinfection.

Question 37

Latent infections

Answer 37

Latent infections are also preceded by an acute infection. The virus lies dormant and does not replicate, but periodic reactivation of the virus can occur with reactivation of symptoms