The Annals of Ibadan Postgraduate Medicine (Journal of the Association of Resident Doctors, U.C.H. Chapter) is published bi-annually.

D.Y. Buowari1 , and H.D. Ogundipe2

  1. Department of Accident and Emergency, University of Port Harcourt Teaching Hospital, Port Harcourt, Rivers State, Nigeria
  2. Department of Surgery, University College Hospital, Ibadan, Oyo State, Nigeria


Background: New strains of different organisms, three of which has been caused by betacorona viruses (SARS-CoV, MERS-CoV and SARSCoV-2) have caused epidemics and pandemics. The COVID-19, caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) started in China in December 2019 has spread globally. Understanding its pattern of spread and how it affects the populace helps to guide formulation of strategies at curbing its spread, managing the disease and allocation of limited resources in tackling the pandemic.

Methodology: This is a review article about the epidemiology of the coronavirus disease -2019 (COVID-19). Various search engines were used to accumulate literature on the topic; these include PubMed, Google scholar, Ajol.

Result: As at October 29, 2020, SARSCoV2 has spread to all continents except the Antarctica. Though a zoonotic disease, human to human transmission has resulted to this pandemic is via direct and indirect contact of droplets with mucosal surfaces. Most severe cases occur among the elderly, males, and people with co-morbid diseases. The average incubation period is 2-10 days. When compared with SARSCoV (Ro: 2.3-3.7, mortality rate 11%) and MERS-CoV (Ro: 0.8-1.3, mortality rate: 34.3%), SARS-Cov-2 is a highly infective (Ro: as high as 6.5) with low mortality rates (average range mortality rates 1.83- 6.3%).

Conclusion: COVID-19 is a highly infective novel virus. Older persons and people with medical comorbidities are more susceptible to the severe form of the disease and mortality. As the second wave comes on, a sustainable measure of limiting the spread and consequences of COVID-19 should be more emphasized.

Keywords: : Coronavirus, Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), COVID-19, Epidemiology, pandemic.


Dr. D.Y. Buowari

Department of Accident and Emergency,

University of Port Harcourt Teaching Hospital,

Port Harcourt,

Rivers State,




An epidemic is a sudden outbreak of an infectious disease in a particular geographical location1 while a pandemic is described as an epidemic occurring worldwide crossing international boundaries and usually affecting a large number of people.2 An influenza pandemic occurs when a new influenza virus emerges and spreads around the world.3The outbreak of diseases depends on several factors some of which are, the type and infectivity of organism, mode of transmission of the disease, presence of population immunity, and number people exposed to it.3

Brief History of Common Epidemics/Pandemics

All pandemics that have occurred were caused by new strains of viruses4 , most being zoonotic diseases passed on from animals to man. 5 Due to their highly contagious nature, the infection spreads rapidly and widely among human population within a very short period.6 Several pandemics have occurred over the years with the latest being the SARS-CoV-2.

The Spanish flu, tagged as the worst pandemic ever, produced a devastating disease between 1918-1919, occurred in three waves and killed 20-40 million people globally.,7,8

The swine flu also known as the pig flu is caused by the swine influenza virus was first isolated in a pig for the first time in 1930 and has been the cause of sporadic outbreaks in pigs and humans.7 The first case of human swine flu pandemic occurred in 2009 affecting 135 countries with 94,512 cases and 429 deaths.9

The Zika virus caused an epidemic in Brazil between 2015-2016 with 1,500,000 cases.10,11 The virus was named after the zika forest where it was first isolated in Uganda in 1947, it is transmitted through a bite from an infected Aedes mosquito species.11

The Ebola virus causing Ebola viral heamorrhagic disease derives its name from the Ebola River in the Democratic Republic of Congo, where it was first isolated. It is transmitted to man by eating an infected fruit bat and has caused several sporadic epidemics over the years and has a mortality rate of 90%. The first outbreak of the disease occurred in 1976 in South Sudan and Zaire (now Democratic Republic of the Congo) 12 and the latest occurred between 2014 and 2016.13 

By 2020, three of the epidemics/pandemics so far experienced have been caused by the novel strains of the beta coronaviruses with influenza-like symptoms, the Severe Acute Respiratory Syndrome coronavirus (SARS-CoV), the Middle East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome coronavirus -2 (SARS CoV-2).14

SARS CoV caused an outbreak in China in 2002 with pneumonia-like symptoms15with 29 countries affected. From 2002 to 2003, there were 8,422 cases and 916 deaths and a mortality rate of 11%.16 

MERS-CoV infected man through direct and indirect contact with dromedary camels and camel products started an outbreak in the Kingdom of Saudi Arabia 2012.17-19. By 2019, it has spread to 5 continents involving 27 countries with 2,499 confirmed cases and 858 deaths and a mortality of 34.5%.20