Human-to-human transmission

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Human-to-human transmission (HHT) is an epidemiologic vector, [1] [2] [3] [4] [5] [6] [7] [8] especially in case the disease is borne by individuals known as superspreaders. In these cases, the basic reproduction number of the virus, which is the average number of additional people that a single case will infect without any preventative measures, can be as high as 203.9. [9] [10] Interhuman transmission is a synonym for HHT. [11]

Contents

The World Health Organization designation of a pandemic hinges on the demonstrable fact that there is sustained HHT in two regions of the world. [12]

Synopsis

Relevant microbes may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, spraying of liquids, toilet flushing or any activities which generate aerosol particles or droplets or generate fomites, such as raising of dust. [13] [14]

Transfer efficiency depends not only on surface, but also on pathogen type. For example, avian influenza survives on both porous and non-porous materials for 144 hours. [13]

The microbes may also be transmitted by poor use of cutlery or improper sanitation of dishes or bedlinen. Particularly problematic are toilet practices, which lead to the fecal–oral route. STDs are by definition spread through this vector.[ citation needed ]

List of HHT diseases

Examples of some HHT diseases are listed below.[ citation needed ]

Related Research Articles

A zoonosis or zoonotic disease is an infectious disease of humans caused by a pathogen that can jump from a non-human to a human and vice versa.

<span class="mw-page-title-main">Epidemic</span> Rapid spread of disease affecting a large number of people in a short time

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.

<span class="mw-page-title-main">Rhinovirus</span> Genus of viruses (Enterovirus)

The rhinovirus is a positive-sense, single-stranded RNA virus belonging to the genus Enterovirus in the family Picornaviridae. Rhinovirus is the most common viral infectious agent in humans and is the predominant cause of the common cold.

<span class="mw-page-title-main">Coronavirus</span> Subfamily of viruses in the family Coronaviridae

Coronaviruses are a group of related RNA viruses that cause diseases in mammals and birds. In humans and birds, they cause respiratory tract infections that can range from mild to lethal. Mild illnesses in humans include some cases of the common cold, while more lethal varieties can cause SARS, MERS and COVID-19. In cows and pigs they cause diarrhea, while in mice they cause hepatitis and encephalomyelitis.

<span class="mw-page-title-main">Mpox</span> Viral disease of humans and animals

Mpox is an infectious viral disease that can occur in humans and other animals. Symptoms include a rash that forms blisters and then crusts over, fever, and swollen lymph nodes. The illness is usually mild, and most infected individuals recover within a few weeks without treatment. The time from exposure to the onset of symptoms ranges from three to seventeen days, and symptoms typically last from two to four weeks. However, cases may be severe, especially in children, pregnant women, or people with suppressed immune systems.

<i>Influenza A virus</i> Species of virus

Influenza A virus (IAV) is the only species of the genus Alphainfluenzavirus of the virus family Orthomyxoviridae. It is a pathogen with strains that infect birds and some mammals, as well as causing seasonal flu in humans. Mammals in which different strains of IAV circulate with sustained transmission are bats, pigs, horses and dogs; other mammals can occasionally become infected.

An emergent virus is a virus that is either newly appeared, notably increasing in incidence/geographic range or has the potential to increase in the near future. Emergent viruses are a leading cause of emerging infectious diseases and raise public health challenges globally, given their potential to cause outbreaks of disease which can lead to epidemics and pandemics. As well as causing disease, emergent viruses can also have severe economic implications. Recent examples include the SARS-related coronaviruses, which have caused the 2002–2004 outbreak of SARS (SARS-CoV-1) and the 2019–2023 pandemic of COVID-19 (SARS-CoV-2). Other examples include the human immunodeficiency virus, which causes HIV/AIDS; the viruses responsible for Ebola; the H5N1 influenza virus responsible for avian influenza; and H1N1/09, which caused the 2009 swine flu pandemic. Viral emergence in humans is often a consequence of zoonosis, which involves a cross-species jump of a viral disease into humans from other animals. As zoonotic viruses exist in animal reservoirs, they are much more difficult to eradicate and can therefore establish persistent infections in human populations.

An attenuated vaccine is a vaccine created by reducing the virulence of a pathogen, but still keeping it viable. Attenuation takes an infectious agent and alters it so that it becomes harmless or less virulent. These vaccines contrast to those produced by "killing" the pathogen.

A reverse zoonosis, also known as a zooanthroponosis or anthroponosis, is a pathogen reservoired in humans that is capable of being transmitted to non-human animals.

<span class="mw-page-title-main">Introduction to viruses</span> Non-technical introduction to viruses

A virus is a tiny infectious agent that reproduces inside the cells of living hosts. When infected, the host cell is forced to rapidly produce thousands of identical copies of the original virus. Unlike most living things, viruses do not have cells that divide; new viruses assemble in the infected host cell. But unlike simpler infectious agents like prions, they contain genes, which allow them to mutate and evolve. Over 4,800 species of viruses have been described in detail out of the millions in the environment. Their origin is unclear: some may have evolved from plasmids—pieces of DNA that can move between cells—while others may have evolved from bacteria.

<span class="mw-page-title-main">Virus</span> Infectious agent that replicates in cells

A virus is a submicroscopic infectious agent that replicates only inside the living cells of an organism. Viruses infect all life forms, from animals and plants to microorganisms, including bacteria and archaea. Viruses are found in almost every ecosystem on Earth and are the most numerous type of biological entity. Since Dmitri Ivanovsky's 1892 article describing a non-bacterial pathogen infecting tobacco plants and the discovery of the tobacco mosaic virus by Martinus Beijerinck in 1898, more than 11,000 of the millions of virus species have been described in detail. The study of viruses is known as virology, a subspeciality of microbiology.

<span class="mw-page-title-main">Influenza</span> Infectious disease

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 one to four days after exposure to the virus and last for about two to eight days. Diarrhea and vomiting can occur, particularly in children. Influenza may progress to pneumonia from the virus or a subsequent bacterial infection. Other complications include acute respiratory distress syndrome, meningitis, encephalitis, and worsening of pre-existing health problems such as asthma and cardiovascular disease.

<span class="mw-page-title-main">Airborne transmission</span> Disease transmission by airborne particles

Airborne transmission or aerosol transmission is transmission of an infectious disease through small particles suspended in the air. Infectious diseases capable of airborne transmission include many of considerable importance both in human and veterinary medicine. The relevant infectious agent may be viruses, bacteria, or fungi, and they may be spread through breathing, talking, coughing, sneezing, raising of dust, spraying of liquids, flushing toilets, or any activities which generate aerosol particles or droplets.

A fomite or fomes is any inanimate object that, when contaminated with or exposed to infectious agents, can transfer disease to a new host.

<span class="mw-page-title-main">Adolfo García-Sastre</span> Spanish and American academic

Adolfo García-Sastre,(born in Burgos, 10 October 1964) is a Spanish professor of Medicine and Microbiology and co-director of the Global Health & Emerging Pathogens Institute at the Icahn School of Medicine at Mount Sinai in New York City. His research into the biology of influenza viruses has been at the forefront of medical advances in epidemiology.

<span class="mw-page-title-main">2003 Midwest monkeypox outbreak</span> Outbreak of monkeypox in the United States

An outbreak of human monkeypox began in May 2003 in the United States. By July, a total of 71 cases were found in six Midwestern states including Wisconsin, Indiana (16), Illinois (12), Kansas (1), Missouri (2), and Ohio (1). The cause of the outbreak was traced to three species of African rodents imported from Ghana on April 9, 2003, into the United States by an exotic animal importer in Texas. These were shipped from Texas to an Illinois distributor, who housed them with prairie dogs, which then became infected.

Raccoonpox virus (RCN) is a double-stranded DNA virus and a member of the orthopoxviruses in the family Poxviridae and subfamily Chordopoxvirinae. Vertebrates are the natural host of Chordopoxvirinae subfamily viruses. More specifically, raccoons are the natural hosts of RCN. RCN was isolated in 1961 from the upper respiratory tissues of 2 raccoons in a group of 92 observably healthy raccoons trapped close to Aberdeen, Maryland.

<span class="mw-page-title-main">Wuhan Institute of Virology</span> Research Institute in Wuhan, Hubei, China

The Wuhan Institute of Virology, Chinese Academy of Sciences is a research institute on virology administered by the Chinese Academy of Sciences (CAS), which reports to the State Council of the People's Republic of China. The institute is one of nine independent organisations in the Wuhan Branch of the CAS. Located in Jiangxia District, Wuhan, Hubei, it was founded in 1956 and opened mainland China's first biosafety level 4 (BSL-4) laboratory in 2018. The institute has collaborated with the Galveston National Laboratory in the United States, the Centre International de Recherche en Infectiologie in France, and the National Microbiology Laboratory in Canada. The institute has been an active premier research center for the study of coronaviruses.

<span class="mw-page-title-main">Transmission of COVID-19</span> Mechanisms that spread coronavirus disease 2019

The transmission of COVID-19 is the passing of coronavirus disease 2019 from person to person. COVID-19 is mainly transmitted when people breathe in air contaminated by droplets/aerosols and small airborne particles containing the virus. Infected people exhale those particles as they breathe, talk, cough, sneeze, or sing. Transmission is more likely the closer people are. However, infection can occur over longer distances, particularly indoors.

Gain-of-function research is medical research that genetically alters an organism in a way that may enhance the biological functions of gene products. This may include an altered pathogenesis, transmissibility, or host range, i.e., the types of hosts that a microorganism can infect. This research is intended to reveal targets to better predict emerging infectious diseases and to develop vaccines and therapeutics. For example, influenza B can infect only humans and harbor seals. Introducing a mutation that would allow influenza B to infect rabbits in a controlled laboratory situation would be considered a gain-of-function experiment, as the virus did not previously have that function. That type of experiment could then help reveal which parts of the virus's genome correspond to the species that it can infect, enabling the creation of antiviral medicines which block this function.

References

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  13. 1 2 Cook 2013, p. 208.
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