Portal:Viruses

Ebola virus disease is a viral haemorrhagic fever of humans and other primates caused by ebolaviruses, RNA viruses in the Filoviridae family. The natural host is thought to be megabats. The virus spreads by contact with body fluids, such as blood. After an incubation period of 2–21 days, nonspecific symptoms including fever, sore throat, muscle pain and headache develop, followed by vomiting, diarrhoea, rash, liver and kidney impairment, and sometimes internal or external bleeding. On average, around half of those infected die, often from hypovolaemic shock. The virus sometimes persists in semen or breast milk for several weeks or months after recovery.

The disease was first identified in 1976 by Peter Piot and others in two simultaneous outbreaks, one in Nzara, Sudan and the other in Yambuku, then in Zaire, near the Ebola River, for which the disease is named. Outbreaks have occurred intermittently in tropical regions of sub-Saharan Africa, with a few thousand cases documented before the epidemic in Western Africa of 2013–16, in which nearly 29,000 cases with more than 11,000 deaths were reported. More than 3000 cases were documented in a subsequent epidemic in the Democratic Republic of the Congo in 2018–20, with more than 2000 deaths. Prevention of outbreaks focuses on limiting virus transmission from infected animals to humans, for example, by taking precautions when handling bush meat. Ebola vaccines are now available. Monoclonal antibody treatments can improve outcomes, and a combination of three monoclonals has been licensed.

Muhammad ibn Zakariya al-Razi was a Persian physician and chemist who, in the 9th century, was the first to document the distinction between the diseases of measles and smallpox.

Credit: Gerard of Cremona (c. 1250–60)

Map showing the prevalence of SARS-CoV-2 cases; black: highest prevalence; dark red to pink: decreasing prevalence; grey: no recorded cases or no data

26 February: In the ongoing pandemic of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), more than 110 million confirmed cases, including 2.5 million deaths, have been documented globally since the outbreak began in December 2019. WHO

18 February: Seven asymptomatic cases of avian influenza A subtype H5N8, the first documented H5N8 cases in humans, are reported in Astrakhan Oblast, Russia, after more than 100,0000 hens died on a poultry farm in December. WHO

14 February: Seven cases of Ebola virus disease are reported in Gouécké, south-east Guinea. WHO

7 February: A case of Ebola virus disease is detected in North Kivu Province of the Democratic Republic of the Congo. WHO

4 February: An outbreak of Rift Valley fever is ongoing in Kenya, with 32 human cases, including 11 deaths, since the outbreak started in November. WHO

21 November: The US Food and Drug Administration (FDA) gives emergency-use authorisation to casirivimab/imdevimab, a combination monoclonal antibody (mAb) therapy for non-hospitalised people twelve years and over with mild-to-moderate COVID-19, after granting emergency-use authorisation to the single mAb bamlanivimab earlier in the month. FDA 1, 2

18 November: The outbreak of Ebola virus disease in Équateur Province, Democratic Republic of the Congo, which started in June, has been declared over; a total of 130 cases were recorded, with 55 deaths. UN

Vaccination or immunisation is the administration of immunogenic material (a vaccine) to stimulate an individual's immune system to develop adaptive immunity to a virus or other pathogen, and so develop protection against an infectious disease. The active agent of a vaccine may be intact but inactivated or weakened forms of the pathogen, or purified highly immunogenic components, such as viral envelope proteins. Smallpox was the first disease for which a vaccine was produced, by Edward Jenner in 1796.

Vaccination is the most effective method of preventing infectious diseases and can also ameliorate the symptoms of infection. When a sufficiently high proportion of a population has been vaccinated, herd immunity results. Widespread immunity due to mass vaccination is largely responsible for the worldwide eradication of smallpox and the elimination of diseases such as polio from much of the world. Since their inception, vaccination efforts have met with objections on scientific, ethical, political, medical safety and religious grounds, and the World Health Organization considers vaccine hesitancy an important threat to global health.

The last recorded smallpox death occurred during the 1978 smallpox outbreak in Birmingham, UK. The outbreak resulted from accidental exposure to the Abid strain of Variola major, from a laboratory, headed by Henry Bedson, at the University of Birmingham Medical School – also associated with an outbreak in 1966. Bedson was investigating strains of smallpox known as whitepox, considered a potential threat to the smallpox eradication campaign, then in its final stages.

A medical photographer who worked on the floor above the laboratory showed smallpox symptoms in August and died the following month; one of her contacts was also infected but survived. The government inquiry into the outbreak concluded that she had been infected in late July, possibly via ducting, although the precise route of transmission was subsequently challenged. The inquiry criticised the university's safety procedures. Bedson committed suicide while under quarantine. Radical changes in UK research practices for handling dangerous pathogens followed, and all known stocks of smallpox virus were concentrated in two laboratories.

Viruses & Subviral agents: bat virome • elephant endotheliotropic herpesvirus • HIV • introduction to viruses • Playa de Oro virus • poliovirus • prion • rotavirus • virus

Diseases: colony collapse disorder • common cold • croup • dengue fever • gastroenteritis • Guillain–Barré syndrome • hepatitis B • hepatitis C • hepatitis E • herpes simplex • HIV/AIDS • influenza • meningitis • myxomatosis • polio • pneumonia • shingles • smallpox

Epidemiology & Interventions: 2007 Bernard Matthews H5N1 outbreak • Coalition for Epidemic Preparedness Innovations • Disease X • 2009 flu pandemic • HIV/AIDS in Malawi • polio vaccine • Spanish flu • West African Ebola virus epidemic

Virus–Host interactions: antibody • host • immune system • parasitism • RNA interference

Methodology: metagenomics

Social & Media: And the Band Played On • Contagion • "Flu Season" • Frank's Cock • Race Against Time: Searching for Hope in AIDS-Ravaged Africa • social history of viruses • "Steve Burdick" • "The Time Is Now" • "What Lies Below"

People: Brownie Mary • Macfarlane Burnet • Bobbi Campbell • Aniru Conteh • people with hepatitis C • HIV-positive people • Bette Korber • Henrietta Lacks • Linda Laubenstein • Barbara McClintock • poliomyelitis survivors • Joseph Sonnabend • Eli Todd • Ryan White