An epidemic is the rapid spread of disease to a large number of hosts in a given population within a short period of time. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.
Epidemiology is the study and analysis of the distribution, patterns and determinants of health and disease conditions in a defined population.
The 1918–1920 flu pandemic, also known as the Great Influenza epidemic or by the common misnomer Spanish flu, was an exceptionally deadly global influenza pandemic caused by the H1N1 influenza A virus. The earliest documented case was March 1918 in the state of Kansas in the United States, with further cases recorded in France, Germany and the United Kingdom in April. Two years later, nearly a third of the global population, or an estimated 500 million people, had been infected in four successive waves. Estimates of deaths range from 17 million to 50 million, and possibly as high as 100 million, making it one of the deadliest pandemics in history.
Mathematical models can project how infectious diseases progress to show the likely outcome of an epidemic and help inform public health and plant health interventions. Models use basic assumptions or collected statistics along with mathematics to find parameters for various infectious diseases and use those parameters to calculate the effects of different interventions, like mass vaccination programs. The modelling can help decide which intervention(s) to avoid and which to trial, or can predict future growth patterns, etc.
The Hong Kong flu, also known as the 1968 flu pandemic, was a flu pandemic whose outbreak in 1968 and 1969 killed between one and four million people globally. It is among the deadliest pandemics in history, and was caused by an H3N2 strain of the influenza A virus. The virus was descended from H2N2 through antigenic shift, a genetic process in which genes from multiple subtypes are reassorted to form a new virus.
Flu season is an annually recurring time period characterized by the prevalence of an outbreak of influenza (flu). The season occurs during the cold half of the year in each hemisphere. It takes approximately two days to show symptoms. Influenza activity can sometimes be predicted and even tracked geographically. While the beginning of major flu activity in each season varies by location, in any specific location these minor epidemics usually take about three weeks to reach its pinnacle, and another three weeks to significantly diminish.
An influenza pandemic is an epidemic of an influenza virus that spreads across a large region and infects a large proportion of the population. There have been six major influenza epidemics in the last 140 years, with the 1918 flu pandemic being the most severe; this is estimated to have been responsible for the deaths of 50–100 million people. The most recent, the 2009 swine flu pandemic, resulted in under 300,000 deaths and is considered relatively mild. These pandemics occur irregularly.
In epidemiology, the excess deaths or excess mortality is a measure of the increase in the number deaths during a time period and/or in a certain group, as compared to the expected value or statistical trend during a reference period or in a reference population. It may typically be measured in percentage points, or in number of deaths per time unit.
Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin from one to four days after exposure to the virus and last for about 2–8 days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia, which can be caused by the virus or by a subsequent bacterial infection. Other complications of infection include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.
Stephen S. Morse is an American epidemiologist, influenza researcher and specialist on emerging infectious diseases, who has served as an adviser on the epidemiology of infectious diseases and on improving disease early warning systems to numerous government and international organizations. As of 2016, he is Professor of Epidemiology at the Mailman School of Public Health of Columbia University. His seminal book Emerging Viruses (1993) was selected by American Scientist for its list of "100 Top Science Books of the 20th Century".
Ira M. Longini is an American biostatistician and infectious disease epidemiologist.
Neil Morris Ferguson is a British epidemiologist and professor of mathematical biology, who specialises in the patterns of spread of infectious disease in humans and animals. He is the director of the Jameel Institute, and of the MRC Centre for Global Infectious Disease Analysis, and head of the Department of Infectious Disease Epidemiology in the School of Public Health and Vice-Dean for Academic Development in the Faculty of Medicine, all at Imperial College London.
Azra Catherine Hilary Ghani is a British epidemiologist who is a professor of Infectious Disease Epidemiology at Imperial College London. Her research considers the mathematical modelling of infectious diseases, including malaria, bovine spongiform encephalopathy and coronavirus. She has worked with the World Health Organization on their technical strategy for malaria. She is associate director of the MRC Centre for Global Infectious Disease Analysis.
Caitlin M. Rivers is an American epidemiologist who as Senior Scholar at the Johns Hopkins Center for Health Security and assistant professor at the Johns Hopkins Bloomberg School of Public Health, specializing on improving epidemic preparedness. Rivers is currently working on the American response to the COVID-19 pandemic with a focus on the incorporation of infectious disease modeling and forecasting into public health decision making.
The 1957–1958 Asian flu pandemic was a global pandemic of influenza A virus subtype H2N2 that originated in Guizhou in Southern China. The number of excess deaths caused by the pandemic is estimated to be 1–4 million around the world, making it one of the deadliest pandemics in history. A decade later, a reassorted viral strain H3N2 further caused the Hong Kong flu pandemic (1968–1969).
Cécile Viboud is a Staff Scientist based in the Fogarty International Center at the National Institutes of Health, where she is part of the Multinational Influenza Seasonal Mortality Study (MISMS). Viboud specialises in the mortality of infectious disease. Viboud was involved with epidemiological analysis during the COVID-19 pandemic.
The Weekly Epidemiological Record (WER) is a publication of the World Health Organization (WHO) that as of 2020 is in its 95th volume. It is published in English and French with the alternative title of the Relevé épidémiologique hebdomadaire. It aims to rapidly disseminate epidemiological information about outbreaks of diseases under the International Health Regulations and about communicable diseases of public health importance. This includes emerging or re-emerging diseases.
Vittoria Colizza is an Italian scientist, research director at INSERM and a specialist in mathematical modeling of infectious disease and computational epidemiology. In particular, she has carried out research on the modeling of seasonal and pandemic flu, Ebola and the COVID-19 pandemic.
Cheryl Cohen is a South African public health researcher who is a professor at the University of the Witwatersrand. She looks to develop evidence-based policy to reduce the burdens of respiratory diseases. During the COVID-19 pandemic. Cohen investigated the rates of COVID-19 in South Africa.
COVID-19 is predicted to become an endemic disease by many experts. The observed behavior of SARS-CoV-2, the virus that causes COVID-19, suggests it is unlikely it will die out, and the lack of a COVID-19 vaccine that provides long-lasting immunity against infection means it cannot immediately be eradicated; thus, a future transition to an endemic phase appears probable. In an endemic phase, people would continue to become infected and ill, but in relatively stable numbers. Such a transition may take years or decades. Precisely what would constitute an endemic phase is contested.
