Virology Flashcards
Are viruses alive?
No, but are obligate intracellular parasites that infect all forms of life
Potato viruses
Mop-top - yellow spots on centres of leaves Leaf role virus - total yellow leaves Virus X - small and shriveled plant
Nuclear polyhedrosis virus
- foot and moth disease virus
- 6.24 million animals slaughtered in 2001
- cost £20 billion, £333 for every man, woman and child
Total deaths world-wide
- 51.9 million per annum
- 67% other causes
- 33% infectious diseases
10 biggest killers
- Malaria (2.1 m)
- Hepatitis B (1.1 m)
- HIV/AIDS (>1m)
- Measles (>1m)
- Neonatal tetanus (0.5m)
- Whooping cough (0.35m)
- Acute respiratory infections (4.4m)
- Diarrhoeal diseases (3m)
- TB (3.1m)
Infections as killers, developed vs developing countries
- developed: 1%
- developing: 46%
Cancers as killers, developed vs developing countries
- developed: 21%
- developing: 9%
Perinatal and maternal killers, developed vs developing countries
- developed: 1%
- developing: 9%
Circulatory killers, developed vs developing countries
- developed: 46%
- developing: 23%
Respiratory killers, developed vs developing countries
- developed: 8%
- developing 5%
Accidents and other killers, developed vs developing countries
- developed: 23%
- developing: 8%
Virus life cycle
- recognition
- attachment
- penetration
- uncoating
- transcription
- protein synthesis
- replication
- assembly
- lysis and release
Virus growth curve
Latent Period - before first rapid increase Eclipse Period - before second rapid increase Intracellular Virus - first rapid increase Extracellular Virus - second rapid increase
Simple forms of virions
- Naked icosahedral capsid (nucleic acid surrounded by a hexagonal arrangement of protein capsomers)
- Enveloped icosahdral
- Naked helical nucleocapsid (two parallel chains of protein capsomers with nucleic acid between)
- enveloped helical nuclepcapsid
Properties of genome
- type of nucleic acid (DNA or RNA)
- strandedness (single or double stranded)
- linear or circular
- sense: [positive, naked RNA infectious negative, naked RNA non-infectious and needs an enzyme to copy RNA)
- number of segments
- nucleotide sequence
Types of virus DNA molecules
- linear single stranded
- circular single stranded
- linear duplex
- duplex with closed ends
- closed circular duplexes (with and without supercoils)
Types of virus RNA molecules
- linear, single stranded infectious, “positive” strand
- linear, single strand non-infectious “negative” strand
- segmented positive strands
- segmented negative strands
- double strand segmented
- diploid single strands
Sites of virus entry and release
- conjuctiva (eyes)
- respiratory tract
- alimentary tract
- urinogenital tract
- anus
- arthropod
- capillaru
- scratch, injury
- skin
Brain diseases
- HSV
- rabies
- picornaviruses
- HIV
- measles
- mumps
- toga
- bunya
- flavi
- encephalitis
Mouth diseases
- HSV
- coxachie virus
Skin and mucous membrane diseases
- HSV
- VZY
- measles
- rubella
- papilloma
- B19 parvovirus
Liver diseases
- Hepatitis !, B, C, D, E, F
- yellow fever
- CMV
- EBV
Heart diseases
- coxachie virus
Eye diseases
- HSV
- adenovirus
- measles
Nose diseases (common cold)
- rhinovirus
- infleunza
- coronavirus
- RSV
- adenovirus
- parainfluenza
Nose diseases (pharangitis)
- adenovirus
- HSVV
- EBV
- coxachie virus
Nose diseases (lower respiratory)
- influenza
- parainfluenza
- RSV
- adenovirus
Enteric diseases
- rotavirus
- norwalk
- adenovirus
- picornaviruses
Urogenital
- HIV
- HSV
- papilloma
Lymphoid
- EBV
- CMV
General patterns of infection
Acute infection - left peak Persistent infection - constant peak Latent, reactivating infection - larger peaks on each side and smaller in centre Slow virus infection - large peaks on each side and small bumps in middle
Do different diseases have the same incubation periods?
no
Herpes simplex virus features
- envelope glycoproteins
- tegument
- DNA
- lipid envelope
- capsid
Chickenpox
Varicella zoster virus (VZY)
Determinants of viral disease
- target tissue (portal of entry, access of virus to target tissue, tissue tropism of virus, permissiveness of cells for replication)
- viral pathogen (strain)
- immune status (competence of the immune system, prior immunity to the virus)
- cytophathic ability of the birus
- immunopathology
- virus inoculum
- general health of the individual
- genetic make-up of the individual
Mechanisms of virus transmission
- respiratory or salivary spread
- formites (e.g. tissues, clothes)
- sexual contact
- zoonoses (animals, insects [arboviruses])
- blood transfusions, organ transplant, needle sharing
Geographical season
- presence of cofactors or vectors in environment
0 habitat and season for arthropod vectors (mosquitos) - school/university session (close proximity)
- climatic conditions
Respiratory or saliva spread
- flu
- EBV
- mumps
Faecal-oral spread
rotaviruses
Venereal spread
- HSV
- HIV
- warts
Vector
sandfly fever
Vertebrate resevoir
rabies
Vector-vertebrate
yellow fever