Viral Infections Flashcards
What are the key features of adenovirus?
it is non enveloped, ds linear DNA
What infections does adenovirus commonly cause and breifly describe the transmission for each?
- resp tract infections (droplets)
- gastroenteritis (infected food)
- conjuctivitis (swimming pools)
- common cold
- disease caused generally related to mode of transmission
How can adenovirus infection be identified? is this often done?
- ELIZA of stool or PCR of throat swab
- not normally done
What type of virus is norovirus?
a non enveloped single stranded RNA virus
How is norovirus transmitted
faecal oral
aerosols in vomit
it is highly contagious
What disease does norovirus commonly cause?
gasteroenteritis - winer vomiting bug
How can norovirus be identified?
PCR
What are symptoms of norovirus?
nausia, vomiting, diarrhoea, abdopain, weakness, headaches, tempreature normally normal
What type of virus is EBV?
enveloped DNA virus
What does EBV cause?
infective mononucleosis/ glandular fever
Describe the course of infection of EBV?
- initial replication in orophaygeal epithilium causing fever, sore throa, nausia, malaise, headache
- then latent infection of B lymphocytes meaning 2 weeks later hepatomegaly, enlarged lymph nodes, high fever (38+), some jaundice, nausia, light intolerance
How is EBV transmitted?
in saliva
kissing disease
What cancer is EBV associated with?
burkitts lymphoma as it causes over replication of infected cells
What is incubation period of EBV virus?
4- 6 weeks (after infection, symptoms will arise)
What is key sign of EBV on FBC?
very high lyphocytes (and monocytes)
ALT and AST may also be high in late stages, platelets may be low
How is EBV specifically detected?
- specific EBV antibodies can be tested for in blood
- also heterophile negative antibodies
How is infective mononucleosis managed?
- no alcohol for 2 weeks post infection
- no sport for 2-3 weeks
- paracetamol and fluids
- usually self limiting
What are blood test results for someone with hep B or C?
- high bilirubin
- high ALT and AST
- normal- high ALP (bile duct destruction limited)
- Albumin low
- PT and APTT longer (poor coagulation)
How is hep B and C spread?
- verticle transmittion
- sexual contact
- sharing needles (90% of Hep C)
- blood exposure
- needle stick injuries
Is hep B or C more likely to progress to a chronic infection?
hep C (80% become chronic) in hep B only 10% become chronic
Are you more likely to get acute symtoms of Hep C or B infection? What are these symptoms?
Hep B - jaundice - fatigue - abdo pain - anorexia - nausia - vomiting symptoms usually clear in 6 months, hep C usually has no acute symptoms
What is incubation period for hep B?
6 weeks- 6 months
What % of hep B infections and hep C infections present with symptoms?
hep B- 50%
hep C- 80% (neither chronic nor acute symptoms)
What are the effects of chronic hep B and C infections?
both lead to cirrhosis (25%)/ liver disease. very few lead to carcinomas (5%)
How is hep B managed?
- no cure
- try and keep viral load low- lifelong antivirals
- post exposure prohylaxsis can be offered to anyone exposed but not vaccinated
How is hep C managed?
- can be cured by 8-12 week course of drugs
- which has 90% success rate but is expensive
How are Hep B and C prevented?
- Hep B prevented with vaccine against surface antigen (3 doses + booster)
- Hep C no vaccine just risk avoidance
How is hep c diagnosed?
- Hep C antibpdy can be detected at any stage of the disease, even after it has been cured
- viral PCR if the hep C anitbody is present, this will confirm the disease is ongoing/ chronic
Describe the serology changes of someone who has has an acute Hep B infection which clears
- Surface antigen (HbsAg) rises within first 6 weeks and then drops when acute infection cleared, if remains high for more than 6 months- chronic infection
- E- antigen (HbeAg) raises, then drops- indicated highly infectious period
- Core antibody (HbcAb) raises and will remain high for life regardless of chronic or cleared infection (IgM initially, but IgG persists for life)
- e antibody appears and dissapears
- surface antibody is last to appear but will only appear if infection is cleared, it will never be present in chronic infection
What will serology be of someone with chronic hep B infection?
- high surface antigen
- high core antibody
- low surface antibody
What type of virus is HIV?
enveloped single stranded RNA virus
Where doe HIV cells replicated?
Inside cells with CD4+ receptors (T- helper cells)
How is HIV transmitted?
- sexual contact (1/1220)
- tranfusions (90-100%)
- needle stick injury (1/333)
- mucous membrane exposure (1/159)
Describe how HIV viruses infect T - helper cells
- binding to CD4 and over receptors
- infection by injecting ss RNA
- reverse transcription (ssRNA-> dsDNA)
- integration of viral DNA into host by integrase
- viral DNA replicated and used to create viral proteins
- proteins come together and bud off
- maturation- proteases cut protein chains which recombine to create working virus
Describe how the viral load and T helper cell number changes throughout a HIV infection
- in first months viral load increases rapidly and a dip is seen in T helper cell number (this stage is usually asymptomatic and they’re highly contagious)
- then viral load drops and t helper cells recover in stage 1
- in stage 2/3 the viral load increases and t helper cells decrease to 500-200 cells/mm^3, symptoms start to arise
- then severe HIV/ AIDS at CD4< 200 cells/ mm^3, serious problems arise
Describe the symptoms of HIV that start to arise in stage 2/3 of the disease
- fever and weight loss
- enlarged lymph nodes
- nausia/ vomiting
- spleno and hepatomegaly
- cough and sore throat (longer than 3 weeks)
- thrush
- kasposi sarcoma (herpres virus/ rash)
- commonly these pts will present in 30s/ 40s
Describe the symptoms of acute HIV infection which often go unnoticed
- fever
- weightloss
- sores and thrush
- rash
- headaches
most go unnoticed/ dismissed for cold
What opportunistic infections are often common with AIDS?
- TB
- PCP
- cryptococcal disease
- taxoplasmosis
- candidiasis
- STIs like gonorrhoea
What are symptoms and investigations for TB?
- weightloss, night sweats, cough, SoB, blood in sputum, headache, meningitis, seizures, joint pain, joint swelling, abdo pain
- do acid fast test (+), do CXR (white), do head CT (often brain legions)
What is PCP? what is its effect?
a fungal infection of resp tract
causes SoB on exertion, dry cough, fatigue, white CXR but normal breath sounds
What is cryptococcal disease and effects?
- fungal infection
- causing headaches, fever, meningism, cough, seizures and coma
What is taxoplasmosis and its effect?
a protozoa
causes cerebral abecesses (ring enhanced legions), seizure, vomiting and coma
What is ghonorrhoea?
- a gram negative diplococcal infection
- often sexually transmitted
- causes a white discharge
How can HIV be tested for?
- serology: HIV antigen and antibody can be tested for after 4 weeks, results available on same day
- PCR: sensitive and early detection but takes a week and is expensive- more used for treatment response than diagonsis
- rapid tests: fingerpricks can be done in home and are accurate if negative but not as much if positive
Who should be tested for HIV?
- those with pneumonia/ TB
- meningitis/ demenita
- psoriasis/ shingles
- diahorrea and unexplained weight loss
- anal cancer and lymphoma
- any STI
What are the types of antiretroviral drugs?
- nucleoside reverse transcriptase inhibitors
- non- nucleoside revers TIs
- protease inhibitors
- integrase inhibitors
- CCR5 (entry) inhibitors
Why should 3 different anti retrovirals be given?
to prevent resistance forming
What is prognosis of HIV on retrovirals??
very good
viral load can be reduced almost so low it cant be transmitted
Give an example of an exclusively acute viral infection?
influenza
polio
What type of viruses tend to become chronic infections?
RNA viruses
Why do chronic infections occur?
viral particles continue to be shed even after acute illness because the host immune system cannot clear it
How is HPV spread?
sexual intercourse, skin- skin contact
What areas are most commonly affected by HPV?
cervix, mouth and throat, anus
What does HPV cause in short and long term?
short term- usually genital worts
long term- linked to cervical cancer
