Portal:Viruses

Cervical cancer is a tumour of the cervix, the part of the uterus that adjoins the vagina in the female reproductive tract. Certain types of human papillomavirus (HPV) are implicated in more than 90% of these cancers, although the great majority of HPV infections of the cervix are not associated with cancer. HPV is transmitted by vaginal sex, infecting cervical epithelial cells. In a minority of cases, infection persists for years, and pre-cancerous changes called cervical intraepithelial neoplasia can develop, which sometimes progress to cancer. Squamous cell carcinomas are the most common. HPV infection is considered essential for nearly all forms of cervical cancer to develop, but other risk factors are also involved, including smoking, HIV infection and other forms of immune suppression, and long-term use of oral contraceptives.

Cervical cancer is the fourth most common cancer in women worldwide. It can be detected by screening; screening every 3–5 years, with appropriate follow-up, can reduce cancer incidence by up to 80%. HPV vaccines protect against high-risk virus strains, and can prevent up to 90% of cervical cancers. Where screening and vaccination are not available, cervical cancer has substantial mortality; worldwide, an estimated 569,000 cases and 311,000 deaths occurred in 2018, with around 85% of cases being in developing countries.

False-coloured scanning electron micrograph of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; gold) emerging from cells in culture. SARS-CoV-2 is a novel coronavirus first identified in China in January 2020 as the cause of an acute respiratory disease now known as COVID-19. Cases of the disease increased rapidly and spread globally, with the World Health Organization characterising COVID-19 as a pandemic in March 2020.

Credit: National Institute of Allergy and Infectious Diseases (19 February 2020)

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 1993 hantavirus outbreak in the Four Corners region of southwest USA was of a novel hantavirus, subsequently named Sin Nombre virus. It caused the previously unrecognised hantavirus pulmonary syndrome – the first time that a hantavirus had been associated with respiratory symptoms. Mild flu-like symptoms were followed by the sudden onset of pulmonary oedema, which was fatal in half of those affected. A total of 24 cases were reported in April–May 1993, with many of those affected being from the Navajo Nation territory. Hantavirus infection of humans generally occurs by inhaling aerosolised urine and faeces of rodents, in this case the deer mouse (Peromyscus; pictured).

Previously documented hantavirus disease had been confined to Asia and Europe, and these were the first human cases to be recognised in the USA. Subsequent investigation revealed undiagnosed cases dating back to 1959, and Navajo people recalled similar outbreaks in 1918, 1933 and 1934.

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