COVID-19 pandemicThe COVID-19 pandemic, also known as the coronavirus pandemic, is a global pandemic of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The novel virus was first identified in an outbreak in the Chinese city of Wuhan in December 2019. Attempts to contain it there failed, allowing the virus to spread to other areas of Asia and later worldwide in 2020. The World Health Organization (WHO) declared the outbreak a public health emergency of international concern (PHEIC) on 30 January 2020.
Index caseThe index case or patient zero is the first documented patient in a disease epidemic within a population, or the first documented patient included in an epidemiological study. It can also refer to the first case of a condition or syndrome (not necessarily contagious) to be described in the medical literature, whether or not the patient is thought to be the first person affected. An index case can achieve the status of a "classic" case study in the literature, as did Phineas Gage, the first known person to exhibit a definitive personality change as a result of a brain injury.
COVID-19Coronavirus disease 2019 (COVID-19) is a contagious disease caused by the virus SARS-CoV-2. The first known case was identified in Wuhan, China, in December 2019. The disease quickly spread worldwide, resulting in the COVID-19 pandemic. The symptoms of COVID‐19 are variable but often include fever, cough, headache, fatigue, breathing difficulties, loss of smell, and loss of taste. Symptoms may begin one to fourteen days after exposure to the virus. At least a third of people who are infected do not develop noticeable symptoms.
Asymptomatic carrierAn asymptomatic carrier is a person or other organism that has become infected with a pathogen, but shows no signs or symptoms. Although unaffected by the pathogen, carriers can transmit it to others or develop symptoms in later stages of the disease. Asymptomatic carriers play a critical role in the transmission of common infectious diseases such as typhoid, HIV, C. difficile, influenzas, cholera, tuberculosis and COVID-19, although the last is often associated with "robust T-cell immunity" in more than a quarter of patients studied.
EbolaEbola, also known as Ebola virus disease (EVD) and Ebola hemorrhagic fever (EHF), is a viral hemorrhagic fever in humans and other primates, caused by ebolaviruses. Symptoms typically start anywhere between two days and three weeks after infection. The first symptoms are usually fever, sore throat, muscle pain, and headaches. These are usually followed by vomiting, diarrhoea, rash and decreased liver and kidney function, at which point some people begin to bleed both internally and externally.
