7- Infectious diseases (3/3) Flashcards
influenza background
RNA virus
- A and B most common
–>A has different H and N subtypes e.g.
* H1N1 – swine flu
* H5N1 – avian flu
- Outbreaks typically in winter
- Spread via respiratory droplets
- Most contagious 24 hours before symptoms start
- Become less infective after 5 to 7 days of illness
Presentation of influenza
- Fever
- Coryzal symptoms
- Lethargy and fatigue
- Anorexia (loss of appetite)
- Muscle and joint aches
- Headache
- Dry cough
- Sore throat
Investigations for influenza
- Diagnosis is based on history, risk factors and clinical presentation
- Viral nasal or throat swabs – PCR analysis (public health like to monitor cases)
management of influenza: healthy person at no risk of complications
NO NEED FOR ANTIVIRALS
Supportive care :
- adequate fluids and rest
- analgesia e.g. paracetamol
management of influenza: person at risk of complications
- Antivirals must be started within 48h of symptom onset to be effective
- Oral oseltamivir 75mg twice daily for 5 days
- Inhaled zanamivir 10mg twice daily for 5 days
influenza post exposure prophylaxis
can be given to higher risk patients e.g. immunosuppressed, within 48 hours of close contact with influenza
- Oral oseltamivir 75mg once daily for 10 days
- Inhaled zanamivir 10mg once daily for 10 days
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
Complications of flu
- 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
tuberculosis background
- Caused by mycobacterium tuberculosis
- Most commonly affects the lungs
o Can also affect lymph glands, brain, kidneys or spine
o More common in children to have TB which affects multiple parts of the body - TB more serious in children
mycobacterium tuberculosis
- Rod shaped bacteria
- Gram staining is ineffective due to waxy coating – acid fast bacilli
- Requires Zeihl Neelson stain (turns bright red against blue background
RF for TB
- More common in non-UK born patients e.g. south Asian
- Immunocompromised e.g. HIV
- Those with close contact with TB
Presentation TB
Tuberculosis usually presents with a history of chronic, gradually worsening symptoms. Most cases are of pulmonary TB (around 70%) but they often have systemic symptoms.
Typical signs and symptoms of TB include:
- Lethargy
- Fever or night sweats
- Weight loss
- Cough with or without haemoptysis
- Lymphadenopathy
- Erythema nodosum
- Spinal pain in spinal TB (also known as Pott’s disease of the spine)
In children specifically
- Failure to thrive
- Wheezing
- Chronic fever
- Chronic cough
TB in children vs adults
BCG vaccine
Bacille Calmette-Guerin
Intradermal infection of live attenuated TB
- Protects against severe and complicated TB – less effective at protecting against pulmonary TB
Prior to vaccine may have a Mantoux test to ensure not already contracted
Who is offered the BCG:
- Neonates born in areas of the UK with high rates of TB
- Neonates with relatives from countries with a high rate of TB
- Neonates with a family history of TB
- Unvaccinated older children and young adults (< 35) who have close contact with TB
- Unvaccinated children or young adults that recently arrived from a country with a high rate of TB
- Healthcare workers
why is diagnosing TB hard
Hard to diagnose because cannot be strained with traditional gram stain- requires Ziehl-Neelson stain
Two tests for immune response to TB- caused by previous, latent or active TB
- Mantoux
- interferon gamma release assay
Two tests for immune response to TB- caused by previous, latent or active TB
Mantoux
- Looks for previous immune response to TB: vaccination or latent or active TB
- Induration of 5mm or more is a positive test result after intradermal injection of tuberculin
Interferon-gamma release assay
- Involves taking a sample of blood and mixing with antigens from TB bacteria
- If person has had previous contact with TB the WBC will be sensitised to those antigens and will release interferon-gamma as part of an immune response
- IGRA test is used in patients who do not have features of active TB but do have a positive Mantoux test to confirm a diagnosis of latent TB
investigations if active TB suspected
- Chest x-ray
- cultures
- NAAT
TB chest x-ray
Primary TB
- May show patchy consolidation, pleural effusions and hilar lymphadenopathy
Reactivated TB
- May show patchy or nodular consolidation with cavitation (gas filled spaces in the lungs) typically in the upper zone
Disseminated miliary TB
- Millet seeds uniformly distributed throughout the lung fields
culturing TB
Cultures
- Bacterial culture useful prior to starting treatment
- Allows testing for resistance to abx
- HOWEVER Cultures can take several months to take several months to grow organisms
Culture collection
- Sputum
- Mycobacterium blood cultures
- Lymph node aspiration
Nucleic acid amplification test: quicker than cultures
Management latent TB
Otherwise healthy patients do not necessarily need treatment for latent TB. Patients at risk of reactivation of latent TB can be treated with either:
* Isoniazid and rifampicin for 3 months
* Isoniazid for 6 months
management acute pulmonary TB
RIPE is the mnemonic used to remember the treatment for TB. It involves a combination of 4 drugs used at the same time:
R – Rifampicin for 6 months
- Red urine and tears
- Inducer of cytochrome P450 – reduces effectiveness of combined pill
- Hepatotoxicity (less likely than adults)
I – Isoniazid for 6 months
- Peripheral neuropathy (pyridoxine (vit B6) should be co-prescribed)
- hepatotoxicity
P – Pyrazinamide for 2 months
- High uric acid levels- gout
- Hepatotoxicity
E – Ethambutol for 2 months
- Colour blindness
- Reduced visual acuity
other managements of TB
Other management
- Test for other infectious diseases (HIV, hepatitis B and hepatitis C).
- Test contacts for TB.
- Notify Public Health of all suspected cases.
- Patients with active TB should be isolated to prevent spread until they are established on treatment (usually 2 weeks). In hospital negative pressure rooms are used to prevent airborne spread. Negative pressure rooms have ventilation systems that actively remove air to prevent it spreading out on to the ward.
- Management and followup should be guided by a specialist MDT.
- Treatment is slightly different for extrapulmonary disease and often includes using corticosteroids.
- Individualised drug regimes are required for multidrug resistant TB.
malaria background
- Infectious disease caused by Plasmodium – protozoan parasite
- Spread through bites from female Anopheles mosquitos that carry the disease
Types of plasmodium
- Plasmodium falciparum is the most severe and dangerous form
- Plasmodium vivax
- Plasmodium ovale
- Plasmodium malariae
life cycle of plasmodium parasite
- Infected blood sucked by by female anopheles mosquito (at night0
- Malaria in anopheles reproduces in gut- sporozoites
- When mosquito bites human sporozoites are injected by mos
- Sporozoites travel to the liver of newly infected person and can lie dormant as hypnozoites for several years (P. vivax and P.ovale)
- Mature into merozoites-> enter blood and infect RBC -> rupture -> release more merozoites -> haemolytic anaemia
Risk factors for malaria
- Young children <5 most vulnerable
- Those with no immunity to malaria e.g. travellers from areas with no malaria are more likely to become very sick and die
management of severe or complicated malaria
IV
Artesunate (most effective not licensed)
Quinine dihydrochloride
main types of viral gastroenteritis
-
Rotavirus
o Most common cause of infantile gastroenteritis
o immunity long lasting (vaccinations)
o Faecal oral route -
Norovirus
o Commonest cause of gastroenteritis in all age groups
o Faecal oral route - Adenovirus less common
