Case fatality rate in the context of "Lethality"

COVID-19 testing involves analyzing samples to assess the current or past presence of SARS-CoV-2, the virus that causes COVID-19 and is responsible for the COVID-19 pandemic. The two main types of tests detect either the presence of the virus or antibodies produced in response to infection. Molecular tests for viral presence through its molecular components are used to diagnose individual cases and to allow public health authorities to trace and contain outbreaks. Antibody tests (serology immunoassays) instead show whether someone once had the disease. They are less useful for diagnosing current infections because antibodies may not develop for weeks after infection. It is used to assess disease prevalence, which aids the estimation of the infection fatality rate.

Individual jurisdictions have adopted varied testing protocols, including whom to test, how often to test, analysis protocols, sample collection and the uses of test results. This variation has likely significantly impacted reported statistics, including case and test numbers, case fatality rates and case demographics. Because SARS-CoV-2 transmission occurs days after exposure (and before onset of symptoms), there is an urgent need for frequent surveillance and rapid availability of results.

Severe acute respiratory syndrome (SARS) is a viral respiratory disease of zoonotic origin caused by the virus SARS-CoV-1, the first identified strain of the SARS-related coronavirus. The first known cases occurred in November 2002, and the syndrome caused the 2002–2004 SARS outbreak. In the 2010s, Chinese scientists traced the virus through the intermediary of Asian palm civets to cave-dwelling horseshoe bats in Xiyang Yi Ethnic Township, Yunnan.

SARS was a relatively rare disease; at the end of the epidemic in June 2003, the incidence was 8,422 cases with a case fatality rate (CFR) of 11%. No cases of SARS-CoV-1 have been reported worldwide since 2004.

The 2013–2016 epidemic of Ebola virus disease, centered in West Africa, was the most widespread outbreak of the disease in history. It caused major loss of life and socioeconomic disruption in the region, mainly in Guinea, Liberia and Sierra Leone. The first cases were recorded in Guinea in December 2013; the disease spread to neighbouring Liberia and Sierra Leone, with minor outbreaks occurring in Nigeria and Mali. Secondary infections of medical workers occurred in the United States and Spain. Isolated cases were recorded in Senegal, the United Kingdom and Italy. The number of cases peaked in October 2014 and then began to decline gradually, following the commitment of substantial international resources.

It caused significant mortality, with a considerable case fatality rate. By the end of the epidemic, 28,616 people had been infected; of these, 11,310 had died, for a case-fatality rate of 40%. As of 8 May 2016, the World Health Organization (WHO) and respective governments reported a total of 28,646 suspected cases and 11,323 deaths (39.5%), though the WHO believes that this substantially understates the magnitude of the outbreak. On 8 August 2014, a Public Health Emergency of International Concern was declared and on 29 March 2016, the WHO terminated the Public Health Emergency of International Concern status of the outbreak. Subsequent flare-ups occurred; the epidemic was finally declared over on 9 June 2016, 42 days after the last case tested negative on 28 April 2016 in Monrovia.

An epidemic of a new variant of clade I mpox (formerly known as monkeypox), called clade 1b, began in Central Africa at least as early as September 2023. As of September 2024, more than 29,000 cases have been reported, with over 800 fatalities (~3% fatality rate), nearly all in the Democratic Republic of the Congo. According to the European CDC: "The size of these outbreaks could be larger than reported due to under-ascertainment and under-reporting."

On 14 August 2024, the World Health Organization declared the epidemic a public health emergency of international concern.