14 Virus 2 Flashcards
human-human transmission involves
> Acutely infected individuals
> Chronic carriers
human-human direct contact example
sexual
human-human environmental
> Faecal oral
> Aerosols
animal-human transmission
- Direct bite
- Insect transmission
- Environmental
- Zoonosis – transmission across species barrier, e.g. SIV=HIV
Respiratory route
Usually takes place following sneezing or coughing
- Inhalation of aerosol droplets
- Contaminated surfaces
- Survival of virus in droplets varies between viruses and ambient temperature
respiratory route - contaminated surfaces
Major transmission of rhinoviruses is hand to eyes / mouth / nose rather than inhalation
what protects against airborne virus
Cilia and mucus provide important physical protection against airborne viruses
Gastrointestinal tract infections
Faecal - oral route
Food and water contamination
Virus must withstand GI tract conditions
Faecal - oral route
Enteroviruses (Coxsackie, Polio etc.), Small Round Structured Viruses
Food and water contamination
- Developing countries
- Poor personal hygiene
- Infants and mentally ill
Virus must withstand GI tract conditions
- Acid stable
- Non-enveloped (bile salts)
what is an effective infection barrier
skin
Transcutaneous Route
skin is overcome by direct inoculation
- Insect or animal bite
- IVDA, needlestick injury and transfusion
Insect or animal bite diseases
> Rabies = animal with “la rage”
> Dengue fever and all arthropod borne viruses = insect bites
IVDA, needlestick injury and transfusion reduced
> Reduced risk by careful handling and screening blood / blood products
Sexual Transmission
Genital tract or rectal mucosa
what increases the transmission of HIV
concomitant STIs
what can viral infections result in
- Acute infection
- Persistent / chronic infection
- Latent infection
Hepatitis B virus (RT DNA virus) contagious
Infectious to other individuals
how many people have Hepatitis B virus (RT DNA virus)
10% become chronic carriers
Hepatitis C virus chronic cases
Chronic infection apparent in 60-80% of cases
HIV persistent infection rates
100%
what does HIV result in
AIDS
what shows latency
herpesvirus
what causes Secondary, or reactivation
Caused by host/environmental factors, usually associated with suppression of immune system
examples of viruses associated with cancer
- Papillomaviruses (cervical cancer)
- Human herpesviruses
In vivo evidence of EBV transformation
B cell lymphoma in immuno suppressed patients, e.g. transplant patients receiving cyclosporin. Reconstitution of immune control = clearance of EBV and frequently tumour
Chronic hepatitis virus infections (hepatocellular carcinoma)
Mechanism of transformation unknown but likely to involve inhibition of apoptosis
CPE
cytopathic effect
cytopathic effect
As virus grows some cells undergo morphological changes
> Primary cell cultures
> Continuous (cancer) cell lines
Diagnostic CPE
> syncytia or multinucleated cells
cell lysis
Inclusion bodies
inclusion bodies
A virus might cause different CPE in different cell lines
what can viral diseases be like
Acute infection can be symptomatic or asymptomatic
outcome can be age-dependent
Early acute symptoms of viral disease symptoms
- fever
- aches
- shivers
what are the virus specific symptoms
- Vesicles in HSV, VZV, Hand Foot and Mouth
- Rash in mumps, measles and rubella
Anogenital warts
- Genital warts associated with cancer
> Vulva, vagina, cervix, peri-anal skin, anal canal and penis
Clinical features - Rash
Vesicles and rashes are collectively known as viral exanthems
Clinical Features – Congenital Infection
TORCH Syndrome
TORCH acronym meaning
(T)oxoplasmosis, (O)ther Agents, (R)ubella (also known as German Measles), (C)ytomegalovirus, and (H)erpes Simplex
