General Features of Viruses

Question 1

how do viruses enter into humans ? and what are the 2 major routes of transmission

Answer 1

thriugh skin or mucous memebreanes

major routes- respiraotry and Faecal-oral

Question 2

give some examples of Respiratory transmisison viruses

Answer 2

Repiratoru tract

• rhinoviruses (common cold)
• influenza
• Covid-19

generalised infections

chicken pox (varicella zoster virus)

small pox (variola virus)

Question 3

how are respiratory viruses spread?

Answer 3

infectious droplets

inhaled directlet

conjucitva then move to RT

finer/soldi srufaces to respiratory tract

Question 4

describe Faecal oral transmisison

Answer 4

imgesting food or water with Faecal contamination

infections increase with poor saniation, poor personal hygiene

Question 5

Examples of common Faecal oral viruses- horizontal transmisission

Answer 5

Picornavirus- Polliovirus (remains endemci in afganistan, nigeria and pakistan)

Hep A

Question 6

Describe Norovirus and why it peaks in winter

Answer 6

V + D

Faecal oral route

winter vommiting disease

more time inside

tire in faeces very high- as few as 18 can cause disease (1640x10⁵) c

Question 7

Describe transmisison of Norovirus

Answer 7

contact with infected individual

contact with doors, handles, tsables

cotnaminated foor /water

aoerol produced form vommit

Question 8

what is vertical transmisison?

give 2 examples

Answer 8

Mother —-> baby

rubella (german measles)

HIV-1 (15%) during birht/ breats milk

Question 9

what are Zoonoses?

Answer 9

non human anima to human (ofent vai biting arthropod)

Question 10

what are Arboviruses?

give examples

Answer 10

those transmitted by Arthropods (gain entry via kin)

dengue fever

yellow fever

St encephaltis

Question 11

what are humans described as in Rabies with regards to further transmission

Answer 11

no vector between infected animal and human

humans are often dead end hosts- no further infections

Question 12

what is pathogenicity?

Answer 12

seveiryt of the disease caused by a virus

Question 13

what are pathogenicity factors?

Answer 13

the characterisitcis that disease casuing viruses posses that alowo them to be pathogenic

Question 14

what is virulence?

Answer 14

severity of disease cuased by different straisn of the same virus

Question 15

describe differen pathogenciity factros

Answer 15

think of the cycle of life of a virus

a apthogneicity factor will help virus do them

Entry

intial replication

immune evasion

dissemination

further replication

(shedding)

Question 16

what is the difference between localsied infection and generalised infection

Answer 16

Local infections- caus einfection with site of entry- typically epithelia or skin (influenza and rhinocirus- repsiraoty epithelium ), norovirus- GI epithelium

Generla infection- cause infections that spread to tagret organs or tissues remote for site of entyr- dissemination in the host

• Polio
• chickenpox
• measles
• Hepatitis ABCE

Question 17

what is Viraemia? what is primary and seconday Viraemia

Answer 17

viraemia is virus in the blood

primary viraemai- spread to regional lymph nodes and entry into blood stream

Generalised infections

secondary viraemia- multplification of virus after entry into anothe rorgan- then re-entyr into blood stream- mulitpilciation and shedding from target organ

Question 18

Explain measles as an exmaple of generalised infection

Answer 18