Section Navigation. Ana M. Hefley, Scott Dee, Diego G. Diel, Raymond R. Rowland, and Megan C. Stoian, T. Hefley, R. Rowland, M. Zimmerman, J. Abstract African swine fever virus is transmissible through animal consumption of contaminated feed. The Study. Figure Figure. Emerg Infect Dis. DOI PubMed. Outbreak of African swine fever, Vietnam, Emergence of African swine fever in China, Transbound Emerg Dis. Survival of viral pathogens in animal feed ingredients under transboundary shipping models.
PLoS One. Infectious dose of African swine fever virus when consumed naturally in liquid or feed. African swine fever spread in China. Vet Rec. African swine fever virus introduction into the EU in Experience of Latvia. Res Vet Sci. The more you know about the project, the more they want to kill you. They especially hate you, Gordon Freeman, personally - because you have cut down quite a few of their buddies. Following the catastrophic Resonance Cascade at the Black Mesa Research Facility , bizarre aliens from Xen teleport into the complex and begin attacking personnel.
The Hazardous Environment Combat Unit is dispatched to the facility to fight the aliens and regain control of Black Mesa. Unknown to the surviving personnel at Black Mesa, though, the Marines have also been ordered to eliminate Black Mesa's civilian personnel to ensure that the incident is covered up.
The HECU rapidly takes over the surface areas of Black Mesa using their V Ospreys to drop in men and then dispatches forces into the interior to eliminate the aliens, Black Mesa Security Force, and bring important members of the Science Team up to the surface for brutal interrogation.
Many Marines disagreed with their orders. The HECU's initial foray into Black Mesa was highly successful: the Marines quickly gained an advantage over the confused and frightened survivors and aliens and established a substantial presence within the facility. Black Mesa's civilian personnel failed to put up any notable resistance, as many personnel mistakenly believed that the Marines were there to rescue them, and those who tried to defend the facility against the HECU were hopelessly outgunned and overwhelmingly outnumbered, having already been weakened by the Xen creatures.
The HECU soon took control of Black Mesa's central command areas and issued orders over the public address system for the facility's remaining personnel to cooperate and submit to interrogation. The troops began fortifying key surface areas with sandbags, mounted machine guns, and fixed artillery. Although there were few of them, there were also some snipers , one of which shot at and fatally wounded a security guard. Surviving facility personnel lent their help to Dr.
Gordon Freeman , who was able to sneak and fight his way across the facility despite all the HECU's actions, being responsible for many casualties on their side. Freeman quickly became a priority target of the troops. Also in the same chapter two Marines can be heard talking about Freeman and their proposed revenge for killing so many of their friends, ignoring the irony of what they themselves had been doing.
Their conversation also hints that the Marines mistakenly believe Freeman and by extension, the whole Black Mesa Science Team intended to cause the Resonance Cascade. As the battle raged on, the Xen aliens began to gain the advantage and the HECU, which was sustaining appalling casualties, was evacuated as aerial bombardments tore into the facility.
Production of interleukin-5 and interferon-gamma by CD4 and CD8 lymphocytes expressing CD30, however, is associated with promotion of B-lymphocyte immunoglobulin production. The primary target of HIV is the immune system itself, which is gradually destroyed.
Viral replication actively continues following initial HIV infection, and the rate of CD4 lymphocyte destruction is progressive. Clinically, HIV infection may appear "latent" for years during this period of ongoing immune system destruction.
During this time, enough of the immune system remains intact to provide immune surveillance and prevent most infections. Eventually, when a significant number of CD4 lymphocytes have been destroyed and when production of new CD4 cells cannot match destruction, then failure of the immune system leads to the appearance of clinical AIDS. Infection with HIV is sustained through continuous viral replication with reinfection of additional host cells.
Thus, the persistent viremia requires continuous reinfection of new CD4 lymphocytes followed by viral replication and infected host cell turnover. Presence or emergence of different HIV subtypes may also account for the appearance of antiretroviral drug resistance as well as the variability in pathologic lesions as different cell types are targeted or different cytopathic effects are elicited during the course of infection.
Phylogenetic studies can identify genetic clusters of HIV-1 env genes which are known as subtypes, or clades, that have arisen with progression of the AIDS epidemic worldwide. The V3 loop amino acid sequences of these genetic variants influence HIV phenotype and immune response. Thus, the biologic properties of HIV can vary, even within an individual HIV infected person, where variants of HIV may arise that are "neurotropic" or "lymphocytotropic" for example.
HIV infects definable population subgroups "risk groups". The transmission of HIV is a function of where the virus appears in the body and how it is shed. HIV can be present in a variety of body fluids and secretions, but the presence of HIV in genital secretions and in blood, and to a lesser extent breast milk, is significant for spread of HIV. However, the appearance of HIV in saliva, urine, tears, and sweat is of no major clinical importance, as transmission of HIV through these fluids does not routinely occur, primarily because of the low concentration of HIV in these fluids.
HIV is primarily spread as a sexually transmissible disease. Transmission of HIV can occur from male to male, male to female, and female to male. Female to female transmission remains extremely rare, though women with same-sex contact are often bisexual and have additional risk factors for HIV infection.
The rate of HIV transmission with sexual intercourse is much lower than with other sexually transmitted diseases-approximately 0. However, some persons have become HIV-infected after a single sexual contact, while other persons have remained uninfected after hundreds of contacts. Sexual contact with persons whose HIV viral load is greater, either with early infection or in the late stage of clinical AIDS, increases the transmission risk.
The presence of cervical ectopia, oral contraceptive use, or pregnancy in women, intact foreskin in men, and genital ulcer disease in either sex increases the risk for HIV infection. Genital ulcers provide a more direct route to lymphatics draining to lymph nodes containing many CD4 lymphocytes and follicular dendritic cells.
Tissue trauma during intercourse does not appear to play a role in HIV transmission. There are many more peripheral blood mononuclear cells capable of either harboring or becoming infected by HIV in blood than are present in other body fluids or secretions. The primary risk group for HIV transmission via blood is intravenous drug users sharing infected needles. Less common practices of blood comingling or use of instruments such as tattoo needles not properly disinfected also carries a potential risk.
Health care workers with percutaneous exposures to HIV-containing blood, however, are infected fewer than 1 in times.
HIV infection can also be acquired as a congenital infection perinatally or in infancy. Mothers with HIV infection can pass the virus transplacentally, at the time of delivery through the birth canal, or through breast milk. Primary HIV infection may go unnoticed in at least half of cases or produce a mild disease which quickly subsides, followed by a long clinical "latent" period lasting years.
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Get ready to eat bugs if you want to live beyond Answer Save. Woke Up Dead Lv 5. There are viruses recovered from egyptian mummies that still functions! Common Cold is caused by viruses, so they can also be "killed" in some way too!
Whether they are alive or not is an issue of language usage, not biology per se.Mar 03, · Defining Life: The Virus Viewpoint. Patrick Forterre. Until very recently, answering this question was often negative and viruses were not considered in discussions on the origin and definition of life. reminiscent of Plato and Socrates’ ideas. It seems to imply that life is an ideal form, concrete examples of life being various Cited by: