Principles of infection 2 Flashcards
What are the general key structural features of viruses?
- Small size
- Can only be seen under electron microscope
- Can be enveloped or non enveloped
- Nucleic acid - DNA or RNA
Describe the herpes simplex virus
- Enveloped
- Size varies between 120 to 300nm
- Can not be seen under light microscope
- Nucleocapsid inside enveloped structure
- In between the nucleocapsid and envelope there is the tegument
- Virus has DNA
What is herpesviridae?
Name of the family of herpes viruses
List members of the herepsviridae
- Varicella zoster virus (chickenpox)
- Epstein Barr virus
- Herpes simplex I
- Herpes simplex II
Describe the Epstein Barr virus
- Causes glandular fever
- DNA
- Enveloped
Describe adenovirus
- No envelope
- DNA virus
- Different ‘serotypes’ of adenoviruses
- Eye infection, respiratory infection, GI infection
Describe papillomavirus
- No envelope
- DNA genome
- Warts
- Cervical cancer
Describe HIV
- RNA virus
- Enveloped
Describe rotavirus
- Non-enveloped
- Small
- Causes diarrhoea
Describe Ebola
- RNA virus
- Enveloped
- Natural reservoir not yet identified
- Infects many cell types
- Migrates from initial site of infection to lymph nodes then liver, spleen, adrenal gland
- Tissue necrosis
- Inflammation
- Organ failure
What are the symptoms of ebola?
Symptoms appear from 2 to 21 days after exposure and ebola is only transmitted once symptoms begin
- Fever
- Headache
- Diarrhoea
- Vomiting
- Stomach pain
- Muscle pain
- Unexplained bleeding or bruising
What is horizontal transmission?
Human to human transmission
- measles
- mumps
- adenoviruses
- influenza
- ebola
What is vertical transmission?
Mother to foetus
E.g. Rubella virus
How is herpes simplex I transmitted?
Oral contact
How is herpes simplex II transmitted?
Sexual contact
How is EBV transmitted?
- Most common is through saliva
- Using saliva contaminated objects can also result in transmission
- Can also be transmitted through blood and semen
How is adenovirus transmitted?
Depends on virus serotype
Respiratory - Droplets
GI - Ingestion of contaminated food or water
Eye - Contact with contaminated objects
How is papillomavirus transmitted?
Skin contact
Sexual contact
How is measles transmitted?
- Contact with infectious droplets
- Airborne transmission
How is mumps transmitted?
Direct contact with saliva or respiratory droplets
How is rabies transmitted?
Animal bites
How is rotavirus transmitted?
Mainly faecal oral
How is ebola transmitted?
- Person to person transmission
- Direct contact with blood or body fluids
- Contaminated objects- needles, syringes
- Can enter through mucous membranes or breaks in skin
- Contact with infected bodily fluids, blood, faeces and vomit
- Also detected in breast milk, urine and semen
How can a viral infection be diagnosed clinically?
- Patient symptoms
- How long have the symptoms existed
- Have there been contacts with sources of infection
- What is circulating in the population
- Location
- Lifestyle
- Other risk factors
How can a viral infection diagnosed in a lab?
- Immunoassay - Looking for antibodies for the virus
- 2 types of antibodies:
- IgM - Indicates recent infection
- IgG - Indicates past infection
- Look for virus by electron microscopy - not used anymore, this is historical data
- Culture virus in cells - light microscopy looking for cytopathic effect - not in common use in diagnostic labs, this is historical
- Culture virus in cells and look for viral proteins in cell cultures
- Use immunofluorescence labelled antibody directed against viral proteins. You can see the viral proteins - Not used in diagnostic labs
What are the current methods used to diagnose viral infections?
- Look for viral RNA/DNA in tissue or blood
- To detect these, the viral DNA or RNA must be amplified
- To amplify the nucleic acid, PCR is used
- Most recent methods use Real Time PCR equipment. Monitors amplification of a targeted DNA molecule during PCR.
