Communicable Diseases Flashcards
What is syndromic surveillance?
- A surveillance approach that relies on clinical case features before confirmation of diagnosis.
- A syndrome = a symptom complex in which the symptoms and/or signs coexist more frequently than would be expected by chance on the assumption of independence.
- Recent interest fuelled by possibility of bioterrorism.
- Rationale for early detection.
- Potential value for detecting emerging infectious diseases and naturally occurring outbreaks.
What is ‘case definition’?
A case definition is a set of standard criteria for deciding whether a person has a particular disease or other healthrelated condition.
- By using a standard case definition we ensure that every case is diagnosed in the same way, regardless of when or where it occurred, or who identified it.
- For potentially severe communicable diseases, where it is important to identify every possible case, health officials use a sensitive, or “loose” case definition.
Case definitions may also be categorised into:
– Suspect
• Usually clinical signs and epidemiologic data.
– Probable
• Meets the suspect case definition plus some additional positive clinical investigations
– Confirmed cases
• Meet the probable case definition plus positive laboratory investigations
Case definitions will generally have what three criteria subheadings?
– Clinical
– Epidemiologic
– Laboratory
What is the Global Outbreak Alert and Response Network?
- A technical collaboration of existing institutions and networks who pool human and technical resources for the rapid identification, confirmation and response to outbreaks of international importance.
- Provides an operational framework to link this expertise and skill to keep the international community constantly alert to the threat of outbreaks and ready to respond.
What three distinct syndromes of severe pneumonia can occur after influenza infection in children or adults?
– primary viral pneumonia
– combined viral–bacterial pneumonia
– secondary bacterial pneumonia
An influenza pandemic occurs when:
– A new subtype of influenza virus emerges in humans to which most people have not been previously exposed and are, therefore, highly susceptible.
– The virus causes serious disease in humans
– The virus is easily and rapidly spread between humans, infecting large numbers of people worldwide and causing many deaths
What is antigenic shift?
A new subtype of influenza can emerge. When this type of major change in the influenza virus occurs, it is known as ‘antigenic shift’.
• Antigenic shift can occur in one of two ways:
– Reassortment, which is the mixing of the genes from an animal or bird virus and a human influenza virus (this is thought to be able to occur if an animal or human is infected with both viruses at the same time)
– Adaptive mutation, which is change in the genes of an animal influenza virus, which may allow the virus to infect and be transmitted easily between humans.
What strategies can be implemented in the event of an influenza pandemic?
Alert and Delay Phases – Preparedness and planning activities – Surveillance and monitoring – Border control – Quarantine and isolation – Social distancing
Contain, Sustain and Control Phases
– Flu clinics
– Social and community support
Antiviral use varies depending on what factors?
– The effectiveness of candidate and customised pandemic vaccine
– The protection offered by natural infection
– The availability of resources
– The anticipated length of time until the customised pandemic vaccine will become available
Antiviral use includes…
– treatment of cases when clinically appropriate
– post-exposure prophylaxis to reduce the risk of infection in people who have not been able to avoid close unprotected contact with an infectious case, such as in health care and some other occupational settings, in households, and in the community (e.g. workplace) in the CONTAIN phase.
Pre-exposure prophylaxis to reduce the likelihood of infection when:
– persons are exposed to an aerosol generating procedure on a case
– there is likely to be ongoing re-exposure to known infectious cases for example, in
influenza services.
• If MAINTENANCE phase is ever encountered, the policy on the use of antivirals may include the need to maintain functioning of critical infrastructure.
– This decision would be made at a whole of government level by the Australian Government in consultation with state and territory governments.
• Depending on resource availability the Australian Government will consider reserving some stocks of antivirals for a possible second wave
Define a biological incident
A biological incident involves the use of microorganisms to produce death or disease in humans, animals, and plants: – bacteria – viruses – fungi – or their toxins
List and define the principle terms in biological agents
- Infectivity - numbers of organisms to cause disease
- Virulence/toxicity - relative severity of disease
- Pathogenicity - capacity of agent to cause disease
- Incubation period - time from exposure to symptoms
- Transmissibility - spread from person to person
- Lethality - ease by which death is caused
- Stability - viability in the environment
What are some epidemiologic clues that indicate a biological incident?
- Epidemic with high illness and death rate.
- Respiratory symptoms predominate.
- Infection non-endemic for region.
- Multiple, simultaneous outbreaks.
- Multi-drug-resistant pathogens.
- Sick or dead animals of multiple types.
- Delivery vehicle or intelligence information.
List and describe the categories of biological agents
- Category A (CDC)
- Easily disseminated or transmitted, high mortality, require special public health preparedness
- Anthrax, Botulism, Plague, Smallpox, Tularemia, Viral Haemorrhagic Fevers
- Category B
- Moderately easily disseminated, moderate morbidity, low mortality, required enhanced surveillance
- Brucellosis, Clostridium Perfringens toxin, food pathogens, Glanders, Meliodosis, Psittacosis, Q fever, Ricin, Typhus, Viral Encephalitis, Waterborne pathogens
- Category C
- Emerging diseases which could be engineered
- Nipah virus, Hantavirus
Describe presentation of inhalational anthrax
May be difficult to diagnosis
• Weaponisation has altered presentation of casualties
• A brief prodrome resembling a “viral-like” illness, characterized by myalgia, fatigue, fever, with or without respiratory symptoms, followed by hypoxia and dyspnoea, often with radiographic evidence of mediastinal widening.
• Meningitis in 50% of patients
List the types of plague
– Bubonic – delivered by contaminated vectors
– Pneumonic – possibility by aerosol
– Septicaemic
What is botulism?
- Produced by seven distinct neurotoxins
- Prevents release of acetylcholine and blocks neurotransmission
- Has been weaponised – can be used as an aerosol or used to contaminate food supplies
What are the symptoms of botulism?
- Ptosis
- Generalised weakness
- Dizziness
- Dry mouth & throat
- Blurred vision
- Diplopia
- Dysarthria
- Dysphonia
- Dysphagia
- Symmetrical descending paralysis
- Development of respiratory failure
What is tularaemia?
- Caused by Francisella tularensis (bacteria)
- Usually acquired by contact with tissue or body fluids of infected animals or via vector (mosquitoes, ticks)
- Has been weaponised and can be disseminated as an aerosol
- Causes a number of manifestations including Typhoidal and Pneumonic tularaemia (respiratory exposure)
What is characteristic of biological incidents?
- Victims of a biological incident may initially go unnoticed (except toxins)
- Detection equipment not readily available
- Victims may not present from one central location
- Health services and hospitals may become overwhelmed
What are the mx priorities in biological agent situations?
• Renewed interest in biological agents requires increased awareness and training of health services personnel
• Recognition is generally on clinical grounds -
detection equipment not readily available
• Report concerns to appropriate public health officials
• Globalism – diseases defy borders
• Basic principles of good hygiene, and quarantine can control disease
List the key points
In most cases biological weapon attack will be completed by time casualties start to develop symptoms.
Use of appropriate precautions and PPE is paramount for protection of healthcare workers.
Early identification and treatment may be effective in most biological weapon agents.
