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pandemics - influenza, coronavirus, Ebola


  • a pandemic is an infectious disease outbreak affecting each of the populated continents
  • these are generally caused by highly infective viruses
  • two contagion factors determine how fast a contagion spreads:
    • generation time
      • the time between when one person becomes infected and when they infect someone else
    • reproduction number or R0
      • the average number of people an infected person goes on to infect
  • once a contagion enters the general community, the phase of sustained transmission commences
  • community mitigation aims to:
    • delay the outbreak peak to buy time for readiness
    • reduce the height of the peak in cases and thereby reduce healthcare burden
    • reduce the overall case numbers and thus reduce morbidity and mortality
    • however, these measures are also likely to prolong the outbreak but as long as the peak is lower then this is desirable
  • community mitigation measures depend upon the mode of transmission of the contagion but may include:
    • hand washing
    • cough etiquette
    • disposing of tisues immediately after they have been used
    • self-quarantine if infected
    • social distancing - cancellation of public events, etc

Global viral outbreaks of significance

year virus countries cases deaths mortality rate
annually (almost) seasonal influenza most 5–15% (340–1000 million) 200,000-700,000 pa1) 0.1-0.2% in USA2) much higher rates in elderly, young, or poor countries
1889 “Russian” flu 1 million (spread by the railways)
1918 “Spanish flu” influenza H1N1 pandemic all 500 million (1/3rd of global population) 50-100 million (3-6% of global population)3) 2-20% (the 2nd wave was much deadlier than the 1st wave and more than 50% of deaths were adults 20-40yrs old as older people may have partial immunity from Russian pandemic of 1889) Australia got the last and less severe wave and had the lowest mortality with only 15,000 deaths however some Aboriginal communities had 50% mortality rates
1957 “Asian” flu H2N2 8–33% (250–1000 million) ~2 million vaccine created; 1.3-3.5%
1968 “Hong Kong” flu H3N2 7–28% (250–1000 million) 1-4 million 0.5%
1996 (but spread was mainly 2003-2007) bird “avian” flu H5N1 18 861 455 60%
2002 SARS virus 29 8096 - was able to be contained and didn't establish itself in communities 774 9.5%
2009 swine flu H1N1 214 >700million 284,500 0.02%
2012-2015 Middle Eastern Respiratory Syndrome - Corona Virus (MERS-CoV) >12 >965 >351 35%
2013-2019 Ebola virus disease (EVD) 10 28,646 11,323 70%
2020 data to 7/3/2020 COVID-19 coronavirus (2019-nCoV / SARS-CoV-2) >50 >100,000 (0.1% of the Hubei population) only 2% are under 20yrs age. It could potentially infect 10-50% of populations without these stringent Chinese control measures 3460 2% (14% if aged over 80yrs)

Effects of global outbreaks and pandemics

direct health effects

  • by their nature, these outbreaks infect a substantive proportion of the population as control becomes more difficult once they get into the general community
  • the rate of infection of a population generally follows a bell curve with a exponential rise and fall
  • each pathogen tends to have a specific case fatality rate which may vary for different ages, and may vary during the course of the outbreak if the pathogen evolves
  • typically the medically vulnerable tend to have the highest case fatality rates such as the very young, the elderly and those with pre-existing co-morbidities, particularly chronic respiratory conditions, cardiovascular disease, diabetes or immunocompromise

indirect health effects

  • demand for health services as a result of an outbreak is likely to create over-whelming pressures on the healthcare system which may reduce access to safe and timely care for not only the outbreak patients but for other patients as well while elective surgery and other services may need to be significantly reduced.
  • outbreaks tend to reduce staffing of healthcare system as well as all other industries which may result in reduced care workers, supply chain shortages, reduced public transport, etc further impacting health care for the population
  • population worry and concern as well as extreme anxiety or paranoia adversely impact the mental health of the population and in particular, those who are vulnerable.

effect of industry, economy and supply

  • quarantine concerns may limit:
    • travel
    • public transport
    • mass gatherings such as conferences, sport events, etc
    • ability for staff to return to work
  • staff shortages from quarantine or illness will force the shutdown or reduction in output of many industries
  • this will lead to supply chain shortages which will have wide ranging impacts:
    • it will expose the many industries which rely on just-in-time (JIT) supply chains which will further impact manufacture or service output as small stockpiles of supplies are rapidly depleted
    • drive mass hysteria into over-purchasing goods and hoarding creating a self-perpetuating hysteria and rush to access perceived “needed goods” - especially those with long expiry dates
    • stock market impacts
    • countries may invoke laws to prevent exports to maintain their own national stockpiles of goods
    • decreased ability to provide healthcare and infection control due to lack of healthcare goods including medicines, PPE gear, antiseptics, etc
    • potential for civil unrest
pandemics.txt · Last modified: 2020/08/21 09:42 by gary1