Infectious Disease Flashcards
(162 cards)
What is influenza?
Influenza is an acute viral infection of the respiratory tract caused by influenza viruses, leading to symptoms such as fever, cough, and muscle aches. It primarily affects the upper and lower respiratory systems.
Influenza viruses are family of _____
Orthomyxoviridae
What type of virus is influenza?
RNA virus
How many types of influenza affect humans?
Three types of influenza, A, B and C, affect humans (a D type affects cattle).
What are the most common types of influenza?
A and B are the most common.
What are the subtypes of Influenza A?
Type A has different H and N subtypes. Examples of A strains are H1N1 (which caused the Spanish flu pandemic of 1918 and the swine flu pandemic of 2009) and H5N1 (which causes bird flu). Influenza A is zoonotic (affects animals + humans), classified by haemagglutinin and neuraminidase proteins (e.g. H1N1).
Outbreaks of flu typically occur during the ____.
winter
Transmission of Influenza
spreads via respiratory droplets, aerosolisation, person-to-person contact, or contaminated surfaces
Incubation period following Influenza exposure ?
ranges from 1-4 days. Viral shedding peaks within 48-72 hours of exposure and rapidly declines following day 6. Viral shedding is usually undetectable by day 10
How often are influenza vaccines given?
Every year the influenza vaccine is altered to target multiple strains that are circulating that year. Yearly vaccines are required. Influenza viruses easily acquire point mutations, resulting in significant antigenic drift over time. This results in seasonal epidemics each year and occasional pandemics
The flu vaccine is free on the NHS to people at higher risk of developing flu or flu-related complications:
Aged 65 and over
Young children
Pregnant women
Chronic health conditions, such as asthma, COPD, heart failure and diabetes
Healthcare workers and carers
How long is the delay between exposure and symptoms of Influenza?
Usually around 2 days
How does Influenza enter the body and start replicating?
Influenza viruses enter the respiratory epithelium through interactions between the viral haemagglutinin protein and cell surface molecules, enabling viral replication to take place.
Acute Influenza Infection leads to what ?
Acute infection triggers a cascade of host responses, including the release of numerous pro-inflammatory cytokines (notably the interferons) and defence mechanisms such as programmed cell apoptosis to minimise viral replication and spread.
This results in mucosal inflammation and eventually progresses to destruction and desquamation of the pseudostratified columnar epithelium. Most influenza infections involve the upper respiratory tract and are self-limiting. However, significant lower respiratory tract infections can develop if the distal bronchial and alveolar epithelium are affected. As alveolar compromise progresses, acute respiratory distress syndrome (ARDS) and viral pneumonia can manifest.
Risk factors for Influenza
Extremes of age (over 90% of deaths occur in over 65s)
Immunocompromise
Comorbidities (e.g. cardiovascular, respiratory, renal disease and diabetes)
Pregnancy
Healthcare workers
Residence in nursing homes or long-term care facilities
Obesity
Symptoms of Influenza
Fever
Lethargy and fatigue
Anorexia (loss of appetite)
Muscle and joint aches
Headache
Dry cough
Sore throat
Coryzal symptoms General malaise accompanied by severe headache, myalgia and fever is a typical presentation of influenza.
Other typical symptoms include:
Pharyngitis
Rhinorrhoea
Dyspnoea
Gastrointestinal (GI) upset, including nausea, vomiting, and diarrhoea are common in children.
Signs of Influenza in uncomplicated infection
clinical findings may be non-specific. Oropharyngeal hyperaemia or cervical lymphadenopathy may be present
Signs of Influenza if there is LRT involvement
Vital sign derangement (e.g. hypoxia, tachycardia, fever, hypotension)
Respiratory distress (e.g. tachypnoea, unable to complete sentences, accessory muscle use)
Wheeze
Crepitations or bronchial breathing on auscultation
Differentials for Influenza Infection
SARS-CoV-2
Bacterial pneumonia
Respiratory syncytial virus
Rhinovirus
Parainfluenza virus
ARDS
Streptococcal pharyngitis
Pulmonary embolism
How can you differentiate common cold and flu?
Flu tends to have an abrupt onset, whereas a common cold has a more gradual onset. Fever is a typical feature of the flu but is rare with a common cold. Finally, people with the flu are “wiped out” with muscle aches and lethargy, whereas people with a cold can usually continue many activities.
What is the diagnostic test for influenza?
Viral PCR
Why is influenza testing done?
Testing may be considered to confirm the diagnosis and monitor circulation and outbreaks.
The ________________ monitors the number of flu cases and provides guidance when the numbers are high.
UK Health Security Agency (UKHSA)
What are the different types of testing available for Influenza?
Point of care tests, Viral nasal or Throat Swabs