18. Viruses and disease Flashcards
1
Q
Describe virus morphology. 3
A
- Helical or icosahedral
- Naked or membrane bound
- Some eg paramyxovirus have membrane studded with proteins derived from the host
2
Q
How are viruses transmitter by inhalation? 4
A
- Via respiratory Tract
- Coughing or sneezing produces clouds of viruses
- Some survive longer in air in winter, colder and more humid
- Droplet nuclei survive longer in air than small vesicles because they are microns wide and don’t sediment as quickly
3
Q
How are viruses transmitted by ingestion? 3
A
- Via gi tract
- These are mostly naked, only membrane bound one knows is corona virus
- Fragile membranes would be dissolved by stomach ph
4
Q
How are viruses transmitted by inoculation? 4
A
- Via skin and mucous membranes
- HIV shared this way by needles etc
- Rabies spread by bites
- Viruses are spread in salve which are injected on biting
5
Q
How are viruses transmitted iatrogenically? 4
A
- Cause unintentionally by Dr for example blood transfusion with HIV virus or transplants
- 50 to 60% of people have CMV but spreading it to those without it by organ transplants can make the patient very ill
- Rabies spreads into the cornea
- The cornea transplant from a person with rabies can reactivate the disease
6
Q
How are viruses transmitted congenitally? 2
A
- This is transmission from mother to fetus for example with rubella
- HIV can pass during in the delivery or during breastfeeding
7
Q
How are labs used to diagnose viruses? 6
A
- Aetiological diagnosis - cause of disease can be established various methods
- PCr or reverse transcriptase PCR can be used to amplify viral DNA or Rna
- Whole virus can be viewed through electromicroscopy
- We can test for the viral antigen through immunological tests for viruses such as HIV
- Specific antibody response - 1gM/1gG in blood
- We don’t use these tests often and as most infections are short lived so this isn’t financially viable
8
Q
What is the picornavieidae family? 6
A
- Small non enveloped icosahedral viruses single-stranded RNA Genomes
- Enteroviruses cause cans problems eg polio
- Hepatovirus causes hepatitis a
- Rhinovirus causes common colds
- Aphthovirus causes foot and mouth in cattle
- This is a huge far as family with diverse genes that show some replication features
9
Q
What is polio? 6
A
- Polio is spread by the faecal oral route 95% of infections are asymtpomatic or subclinical
- It has an incubation period of 1 to 2 weeks with a virus replicates in the lymph glands
- Symptoms include fever fatigue sore throat vomiting and bowel problems
- Can induce meningitis usually resolves itself but sometimes spreads along axons to damage motor end plates leading to flaccid paralysis or paralytic poliomyelitis in 1% of people
- Can lead to complete recovery or cause permanent paralysis and death
- Enterovirus from picornavirus family
10
Q
Describe the polio vaccine. 4
A
- Polio has been eradicated in many countries especially in the developed world due to the vaccine
- Still a problem in Nigeria Afghanistan and Pakistan
- Due to problems with distributing vaccine
- The virus is now being carried into Syria by soldiers
11
Q
Describe the 1950s polio epidemic. 3
A
- Spread rapidly as people didn’t realise they had it
- Lead to paralysis resources tract muscles
- Treated with an iron long negative pressure chamber that some people ended up in full life
12
Q
What are rhinoviruses? 6
A
- Most frequent cause of the trivial common cold for about 100 serotypes
- The virus mutates easily as it has an rna genome with no error-checking mechanism so many serotypes exist at the same time in a single population
- Spread by respiratory droplets
- it has a two to four day incubation period and is infectious for one day after infection until the end of the symptoms
- Causes headaches sneezing sore throat cough
- Spreads generously during the symptom phase
13
Q
Describe influenza viruses. 6
A
- Single-stranded RNA and enveloped
- type a found in most animals especially birds and causes most world epidemics type B is human specific and see is specific to humans and seals
- Symptoms include fever chills aching loss of appetite and wanting to lie down last for 3 to 7 days complete recovery takes about two weeks has an incubation period of 1 to 4 days
- The mucociliary escalator gets destroyed by the virus leading to secondary bacterial pneumonia which kills the elderly and the very young
- 75% of the 4000 UK flu deaths per year or in people aged 55 or above. all the risk groups include asthmatics pregnant women and people with heart disease due to medication
- The vaccine contains the two most common A types and one B type. global work on a vaccine for every strain
14
Q
How is the influenza virus structured? 5
A
- Defined by haemagglutanin of which there are 16 types. only one type can be expressed at the time. humans host h1 to h3
- Also has neuraminidase there are nine types of these we express one to 5
- Aquatic birds are a reservoir for all h and N antigens
- Single-stranded rna has a mutation rate which is 10,000 times greater than human or viral DNA
- Did you know has eight segments and recombination of these lead to crazy flus
15
Q
What influenza epidemics have there been? 6
A
- H1 N1 was the Spanish flu of 1918 this killed more people than the whole of World War I soldiers took the flu home and spread it to their families in 1977 and identical genome was found due to an accidental lab release
- H2 N2 was the 1957 Asian flu recombination of H1 N1 and another avian virus three segments were changed
- H3 N2 was the 1968 Hong Kong flu there was a change in two segments
- H5N1 bird flu wouldn’t spread between people only from birds to person
- H1 N1 is swine flu
- Humans have never been exposed to the H5 antigen before
