Viral infection Flashcards
Influenza: Overview
Acute viral infection of lungs and airways.
The influenza virus is an RNA virus. There are three types: A, B and C, of which A and B are the most common. The A type has different H and N subtypes and you may hear about different strains, for example H1N1 (swine flu) and H5N1 (avian flu). Outbreaks typically occur during the winter.
- Common throughout the world.
- Affects 5-10% of adults.
- Affects 20-30% of children.
- In most, it is a self-limiting illness.
Seasonal influenza: Effect of complications
Complications can be life threatening in:
- Elderly
- Pregnant women
- Those with chronic disease
Influenza: Vaccination
Every year the vaccine is changed to target multiple strains of influenza that are likely to cause flu. It needs to be given yearly to keep the person protected.
It is given free on the NHS people at higher risk of developing flu:
- Aged 65
- Young children
- Pregnant women
- Chronic health conditions such as asthma, COPD, heart failure and diabetes
- Healthcare workers and carers
Influenza: Presentation
- Fever
- Coryzal symptoms
- Lethargy and fatigue
- Anorexia (loss of appetite)
- Muscle and joint aches
- Headache
- Dry cough
- Sore throat
Influenza: Diagnosis
Treatment is usually started based on the history, risk factors and clinical presentation.
Viral nasal or throat swabs can be sent to the local virology lab for polymerase chain reaction (PCR) analysis.
This will confirm the diagnosis and also provide data to public health so that they can monitor the number of cases of influenza.
Influenza: Management
Public health monitor the number of cases of flu and provide guidance on when there is enough flu in the area to justify treating patients with suspected flu.
Healthy patients that are not at risk of complications do not need treatment with antiviral medications. The infection will resolve with self care measures such as adequate fluid intake and rest.
There are two options for treatment in someone presenting with suspected influenza that is at risk of complications of influenza:
- Oral oseltamivir 75mg twice daily for 5 days
- Inhaled zanamivir 10mg twice daily for 5 days
Treatment needs to be started within 48 hours of the onset of symptoms to be ef
Influenza: Post-exposure prophylaxis
Post-exposure prophylaxis can be given to higher risk patients such as those with chronic diseases or immunosuppression within 48 hours of close contact with influenza. This aims to minimise the risk of developing flu and complications.
- Oral oseltamivir 75mg once daily for 10 days
- Inhaled zanamivir 10mg once daily for 10 days
Influenza: Complications
- Otitis media, sinusitis and bronchitis
- Viral pneumonia
- Secondary bacteria pneumonia
- Worsening of chronic health conditions such as COPD and heart failure
- Febrile convulsions (young children)
- Encephalitis
HIV: Definitions
- HIV – Human Immunodeficiency Virus
- AIDS – Acquired Immunodeficiency Syndrome
- AIDS is usually referred to in the UK as Late Stage HIV
HIV: Basics
HIV is an RNA retrovirus. HIV-1 is most common type. HIV-2 is rare outside West Africa.
The virus enters and destroys the CD4 T helper cells. An initial seroconversion flu like illness occurs within a few weeks of infection. T
he infection is then asymptomatic until it progresses and the patient becomes immunocompromised and develops AIDS defining illnesses and opportunistic infections potentially years later.
HIV: Transmission
HIV can’t spread through normal day to day activities including kissing. It is spread through:
- Unprotected anal, vaginal or oral sexual activity.
- Mother to child at any stage of pregnancy, birth or breastfeeding. This is referred to as vertical transmission.
- Mucous membrane, blood or open wound exposure to infected blood or bodily fluids such as through sharing needles, needle-stick injuries or blood splashed in an eye.
HIV: AIDS defining illness
There is a long list of AIDS defining illnesses associated with end stage HIV infection where the CD4 count has dropped to a level that allows for unusual opportunistic infections and malignancies to appear.
Some examples are:
- Kaposi’s sarcoma
- Pneumocystis jirovecii pneumonia (PCP)
- Cytomegalovirus infection
- Candidiasis (oesophageal or bronchial)
- Lymphomas
- Tuberculosis
HIV: Screening
HIV is a treatable condition and most patients are fit and healthy on treatment. There are many people that have HIV that do not know the diagnosis and these patients are at risk of the complications and spreading the disease. Generally the earlier a patient is diagnosed the better the outcome.
We should test practically everyone admitted to hospital with an infectious disease regardless of their risk factors. Patients with any risk factors should be tested. Antibody tests can be negative for 3 months following exposure so repeat testing is necessary if an initial test is negative within 3 months of a potential exposure.
Patients need to give consent for a test. Verbal consent should be documented prior to a test. Consent only needs to be as simple as “are you happy for us to test you for HIV?” Patients no longer require formal counselling or education prior to a test.
HIV: Prevention (4)
- Sexual transmission: condom use
- Post-exposure prophylaxis (PEP)
- Pre-exposure prophylaxis (PrEP)
- Vertical transmission
HIV: Testing (4)
- Viral load
PCR testing for the HIV RNA levels tests directly for the quantity of the HIV virus in the blood and gives a viral load. - HIV antibody test
Most common and accurate test. Usually consists of both a screening ELISA (Enzyme Linked Immuno-Sorbent Assay) test and a confirmatory Western Blot Assay. Most people develop antibodies to HIV at 4-6 weeks but 99% do by 3 months. There is an option for patients to self sample by requesting a kit online and posting a sample of their blood to get tested for the antibody. - p24 antigen test
PCR test. Usually positive from about 1 week to 3 - 4 weeks after infection with HIV (can be positive before antibody test). Sometimes used as an additional screening test in blood banks - CD4 count
Cannot diagnose HIV. Use to monitor immune system function and disease progression in patients with HIV.
HIV: Monitoring (2)
- CD4 count
- Viral load
HIV: Monitoring - CD4 count
This is a count of the number of CD4 cells in the blood. These are the cells destroyed by the HIV virus. The lower the count the higher the risk of opportunistic infection.
- 500-1200 cells/mm3 is the normal range
- Under 200 cells/mm3 is considered end stage HIV / AIDS and puts the patient at high risk of opportunistic infections
HIV: Monitoring - Viral load (VL)
Viral load is the number of copies of HIV RNA per ml of blood.
“Undetectable” refers to a viral load below the labs recordable range (usually 50 – 100 copies/ml).
The viral load can be in the hundreds of thousands in untreated HIV.
HIV: Presentation
- With symptoms of early HIV infection:
- Primary HIV infection (seroconversion)
- Persistent generalised lymphadenopathy - In the asymptomatic, latent phase of chronic HIV infection
- With complication of immune dysfunction
HIV: Needle-stick injury
Risk of HIV transmission from a single needle-stick exposure from a person with HIV not on ART is about 1 in 300 (lower than the risks of hepatitis B and C transmission).
Prevent:
- Use ‘safer sharps’ (incorporates mechanism to minimize accidental injury)
- Do not recap unprotected medical sharps
- When using sharps, ensure there is a disposal container nearby
Manage:
- Encourage the wound to bleed
- Ideally under running water - do not suck
- Wash with soap and running water
- Do not scrub
- Seek advice from occupational health/infection control
regarding source testing + PEP
HIV: seroconversion
HIV seroconversion is symptomatic in 60-80% of patients and typically presents as a glandular fever type illness. Increased symptomatic severity is associated with poorer long term prognosis. It typically occurs 3-12 weeks after infection
Features
- sore throat
- lymphadenopathy
- malaise, myalgia, arthralgia
- diarrhoea
- maculopapular rash
- mouth ulcers
- rarely meningoencephalitis
