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L13 Epidemics, pandemics & Disaster Preparedness Comminicable Disease
L13 Epidemics, pandemics & Disaster Preparedness Comminicable Disease
How is influenza spread?
- infectivity period: 1 day before, 14 days after
- can be transmitted in 3 main ways
- Contact transmission:
- direct: kissing
- indirect: sharing
- Mainly by "droplet" spread:
- coughing, sneezing & talking
- mucous membs
- virus active on heard surfaces for 48 hours
- "Aerosol" spread
- unusual but possible in v crowded conditions
Avian Influenza
-1997- Hong Kong
- 2003-2004- pandemic potential
- 60% fatality rate
- still pandemic potential
H5N1- Basics
- virus affects poultry flocks
- cannot yet easily spread from person to person
- never became pandemic as predicted
To become a Pandemic Virus
- A novel (new) virus which humans have no immunity :check:
- The virus causes sig human illness & death :check:
- Virus can spread easily from person to person :red_cross:
Swine Flu
- influenza pandemic (H1N1) 2009
- 27 April 2009
- USA (40 cases), Mexico (26 cases & 7 deaths) & others
- 1 July 2009: officially a pandemic
- Aus (4090 cases & 7 deaths)
- By the end of the pandemic
Define
Pandemic
- prevalent over a whole country or the world
- when epidemic spread throughout the world
Epidemic
- outbreak of disease tht attacks many ppl at the same time & may spread thru one or several communities
Endemic
- permanently in a particular region population
4 Maj factors influencing the establishment of the disease
- Characs of the Infectious Organism
- Characs of the Host (ind who is infected)
- Characs of Transmission
- Influence of Environment
- Infectious Organism
- Viruses: contain DNA or RNA, dependent on host (c), intra(C)
- eg. measles virus, Hep B virus, poliovirus, HIV
- Bacteria: larger than viruses, can live & grow independently
- eg. streptococci
- Fungi: larger than bacteria eg. Microsporum
- Protozoans: uni(C) parasites eg. plasmodium vivac (malaria)
- Helminths: multi(c) parasites (worm)
- Prions: Prot particles w/o DNA/RNA
Imp features of the org
- lifecycle
- pathogenicity: cap to prod disease
- stability: survival in environment
- reservoir: natural habitat & humans or animals
- source: person, object, or substance from which an organism is passed to a host
- Host
- Host defences:
- skin & mucous memb barriers
- host flora (skin, gut)
- local phys conds of the body (acidity of stomach)
- Immune syst
- natural immunity (some diseases eg. measles, polio but not malaria)
- induced immunity (immunisation eg. measles)
- factors affecting susceptibility
- age ( v young & v old at greatest risk)
- concurrent illness (eg HIV & Tb)
- meds
- nutrition
- gen health
- congenital/genetic abnormalities
- occupational factors
- socioeconomic factors
- Transmission
- Direct
- Indirect
- Transmission via fomites can also occur (ie. objects such as taps, doorknobs)
- determines where intervention can occur
- air-borne: Tb, Influenza (aerosol, droplet): isolation, hygiene
- water-borne: giardia: water treatment/filtration
- blood- borne: syphilis, Hep B, C & HIV
- Environment
- Climate: temp, humidity
- Ecological niches for vector-borne diseases
- depends on which mosquitoes spread the disease
- dengue fever: only transmitted by Aedes egypto
- control of breeding sites
- Sanitation measures (food hygiene, seqnge disposal syst, water services, personal hygiene) to break the chain of transmission
- SE factors: overcrowding
Control of disease
1o prevention
- halting the occurrence of the disease in the first place
- breaking the chain of transmission
- sanitation (sewage, food prep)
- control of vectors
- personal hygiene
- inactivating agent
- disinfectants, heat treatments
- eg. pasteurisation, sterilisation
- increasing host resistance
- immunisation
- improve gen health (eg. nutrition)
2o prevention
- measures taken once outbreak has occurred to limit further spread
- case finding eg. tracing contacts of a person w/ an STI
- management of cases to limit transmission
- eg. antibiotics, advice, isolation
- outbreak investigation
3o prevention
- treatment of ppl who have already been infected to prevent further disability