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Emerging Pandemic Diseases: How We Got to COVID-19


Infectious diseases prevalent in humans and animals are caused by pathogens that once emerged from other animal hosts. In addition to these established infections, new infectious diseases periodically emerge. In extreme cases they may cause pandemics such as COVID-19; in other cases, dead-end infections or smaller epidemics result. Established diseases may also re-emerge, for example by extending geographically or by becoming more transmissible or more pathogenic. Disease emergence reflects dynamic balances and imbalances, within complex globally distributed ecosystems comprising humans, animals, pathogens, and the environment. Understanding these variables is a necessary step in controlling future devastating disease emergences.


I was interested that there are only 4 COV SARS viruses.

I also like the glossary:

“Terms Related to Emerging Infectious Diseases

  • Antigenic immunodominance: Ability of a protein epitope to elicit an immune response greater than the response to one or more adjacent epitopes
  • Cell tropism: Ability of a pathogen to infect a particular cell type
  • Endemic: Noun and adjective denoting prevalence of human infection
  • Enzootic: Noun and adjective denoting prevalence of animal infection
  • Epidemic, Pandemic: Noun and adjective denoting highly incident disease (epidemic) or spread that is global or covers very large geographic areas (pandemic)
  • Epizootic, Panzootic: Noun and adjective analogous to epidemic and pandemic, but with respect to animal diseases
  • Fomite: An inanimate object that transmits infection, e.g., a towel or doorknob
  • Host-Switching, Spillover: Process by which a pathogen adapted to one host species becomes adapted to another host species
  • Disease emergence: Appearance of a disease in a new host
  • Zoonosis: A human infection caused by an animal pathogen that may be either a dead-end infection or that may initiate person-to-person spread”

Look at the history!

Table 1 Emerging Infectious Diseases in History
Year Name Deaths Comments
430 BCE “Plague of Athens” ∼100,000 First identified trans-regional pandemic
541 Justinian plague ( Yersinia pestis) 30–50 million Pandemic; killed half of world population
1340s “Black Death” ( Yersinia pestis) ∼50 million Pandemic; killed at least a quarter of world population
1494 Syphilis ( Treponema pallidum) >50,000 Pandemic brought to Europe from the Americas
c. 1500 Tuberculosis High millions Ancient disease; became pandemic in Middle Ages
1520 Hueyzahuatl ( Variola major) 3.5 million Pandemic brought to New World by Europeans
1793–1798 “The American plague” ∼25,000 Yellow fever terrorized colonial America
1832 2nd cholera pandemic (Paris) 18,402 Spread from India to Europe/Western Hemisphere
1918 “Spanish” influenza ∼50 million Led to additional pandemics in 1957, 1968, 2009
1976–2020 Ebola 15,258 First recognized in 1976; 29 regional epidemics to 2020
1981 Acute hemorrhagic conjunctivitis rare deaths First recognized in 1969; pandemic in 1981
1981 HIV/AIDS ∼37 million First recognized 1981; ongoing pandemic
2002 SARS 813 Near-pandemic
2009 H1N1 “swine flu” 284,000 5th influenza pandemic of century
2014 Chikungunya uncommon Pandemic, mosquito-borne
2015 Zika ∼1,000?  Pandemic, mosquito-borne
Selected important emerging and re-emerging infectious diseases of the past and present, 430 BCE–2020 CE. Mortality estimates are in most cases imprecise; see text.
∗ Zika mortality has not been fully established. Most deaths are fetal or related to outcomes of severe congenital infections.