Acute Respiratory Infections

Question 1

What is MERS-COV?

Answer 1

Middle East Respiratory Syndrome Coronavirus - virus transferred to humans from infected dromodary camels. Identified in Middle East, Africa and South Asia. Ranges from being asymptomatic or mild respiratory symptoms to severe acute respiratory disease and death. Typical presentation is fever, cough and SOB. Pneumonia is a common finding and diarrhoea has been reported, treatment is supportive and based on a patient’s condition.

Question 2

Describe influenza

Answer 2

• Types A and B are more common and serious, type C usually only causes mild respiratory illness
• Influenza is highly contagious, it is transmitted in large droplets when infected patients cough, sneeze or talk
• The influenza virus can remain infectious on surfaces that are not cleaned for up to 24 hrs
• The average incubation period is 2 days (ranging from 1-4 days)
• Individuals are most infectious 24-48 hrs prior to developing symptoms but some never develop symptoms

Question 3

How is influenza spread via person-to-person?

Answer 3

• Direct contact with infectious individuals
• Contact with contaminated surfaces (fomites)
• Inhalation of infectious aerosols

Question 4

How can the flu virus mutate?

Answer 4

• Antigenic drift: gradual accumulation of mutations that change the surface antigens and make the virus less susceptible to the antibodies produced during previous infections
• Antigenic shift: 2 or more strains combine to form a new subtype with surface antigens that humans have not encountered previously.

Question 5

What is the clinical presentation of influenza?

Answer 5

• Usually fever, cough, sore throat, myalgias, frontal or retro-orbital headache, fatigue and conjunctivitis
• Variable and can present as predominant respiratory illness (dry or productive cough, sore throat or nasal discharge) to systemic illness with little resp involvement (muscle aches, severe fatigue, headache)
• Uncomplicated influenza usually improves after 2-5 days although some patients only start getting better after 1 week
• Influenza A causes more severe illness than Flu B

Question 6

What is the definition of uncomplicated influenza?

Answer 6

Influenza presenting with fever, coryza, generalised symptoms (headache, malaise, myalgia, arthralgia) and sometimes GI symptoms but no features of complicated influenza.

Question 7

What is the definition of complicated influenza?

Answer 7

Influenze requiring hospital admission +/or with symptoms and signs of LRTI (hypoxaemia, dyspnoea, lung infiltrates), CNS involvement +/or a significant exacerbation of an underlying medical condition.

Question 8

What are the risk factors for complicated influenza?

Answer 8

• Neurological, hepatic, renal, pulmonary and chronic cardiac disease
• Diabetes mellitus
• Immunosuppression
• Age >65yrs
• Pregnancy (including up to 2 weeks post partum)
• Morbid obesity (BMI >/=40)

Question 9

What are the complications of influenza?

Answer 9

• Primary viral pneumonia: most common in patients with chronic lung problems, the patient gradually worsens from the initial presentation and their SOB, fever, cough progress
• Secondary bacterial pneumonia: superimposed bacterial infection of the lungs usually occurs when the patient’s symptoms from influenza are improving. After improving for 24-48 hours the patient becomes SOB, fever recurs and they may be hypoxic (most common are strep pneumoniae, staph aureus and haemophilius influenzae)
• Myositis and rhabdomyolysis: most common in children but overall rare. A rise in CK with myoglobuminuria and tender/occasionally swollen muscles occurs.
• CNS complications: encephalitis, transverse myelitis, GBS and aseptic meningitis have all been reported

Question 10

What other viruses can cause pneumonia?

Answer 10

Adenovirus, para-influenzae and respiratory syncytial virus - diagnoses with PCR techniques (viral throat swab).

Question 11

What would consolidation indicate on a CXR?

Answer 11

• Bacterial pneumonia

- Aspergillosis

Question 12

What would cavitation indicate on a CXR?

Answer 12

• Mycobacteria
• Histoplasma
• Bacterial pneumonia (S. aureus)
• Aspergillosis

Question 13

What would nodular lesions indicate on a CXR?

Answer 13

• Bacterial pneumonia
• Aspergillosis
• Nocardiosis
• Mucormyosis

Question 14

What would pleural effusion indicate on a CXR?

Answer 14

• Bacterial pneumonia

- TB

Question 15

What would ground glass opacities indicate on a CXR?

Answer 15

• Pneumocystosis
• Viral pneumonia
• Atypical bacteria pneumonia
• Aspergillosis

Question 16

What is the role of Neuraminidase inhibitors?

Answer 16

e. g. oseltamivit and zanamivir
- Worth using them in patients in critical care or those who are headed that way and immunocompromised patients
- Can be used as post-exposure prophylaxis, usually given during outbreak for patients living in those affected areas. Medication needs to be commenced within 48 hrs from time of contact with the infectious individual and taken for 14 days.

Question 17

What high risk groups receive the influenza vaccine?

Answer 17

• All healthcare professionals directly involved in patient care
• People living in long stay care homes i.e. residential or nursing homes
• People with chronic health conditions: chronic liver, kidney, lung, heart or neurological diseases, diabetes or immunosuppressed.
• Pregnant women
• All those >65yrs
• Children aged 2yrs up to year 3

Question 18

What organisms cause pneumonia?

Answer 18

• S. pneumoniae and H. influenzae are the causes of typical pneumonia
• Legionella pneumophila and mycoplasma pneumoniae are the most common causes of atypical pneumonia
• Every year around winter time influenza are important causes of CAP requiring hospital admission
• Pneumocystis jiroveci and cytomegalovirus can cause pneumonia in immunocompromised patients.

Question 19

What is the treatment for pneumonia?

Answer 19

Treatment: co-amoxiclav 1.2g TDS and clarithromycin 500mg BD IV
Meropenum is too broad spectrum and is reserved for HAI e.g. caused by extended spectrum beta-lactamase (ESBL) producing Enterobacteriacae.

Question 20

What are the risk factors for severe influenza infection?

Answer 20

• HIV infection: CD4 <200 considered severe
• Severe primary immunodeficiency
• Leukaemia/lymphoma/multiple myeloma
• Splenectomy
• Recent chemo (up to 6 months ago)
• DMARDs/immunosuppressants (up to 6 months)
• Bone marrow recipients receiving immunosuppression up to 12 months after
• Steroids (40mg per day for 7 days) up to 3 months ago
• Solid organ transplants
• Malnourishment and alcohol excess
• Autoimmune disease
• Renal disease
• Diabetes
• Liver disease
• Pregnancy

Question 21

How is CMV transmitted?

Answer 21

Via infected secretions. When symptomatic, the presentation depends on the site of infection. CMV mononucleosis presents with fever and malaise. Symptoms can be similar to EBV primary infection.