For example, some bacterial and viral infections can have very similar symptoms. Where this sample is collected from depends on your illness and the type of organism suspected. Some sample types can include:. In some cases, they may also want to take a biopsy of the affected tissue to examine it. There are many actions that you can take to prevent the spread of infections. Be sure to follow the tips below:. Infections can be caused by a variety of different organisms, including viruses, bacteria, fungi, and parasites.

The different ways that you can get an infection can be just as diverse as the organisms that cause them. You may need additional medications to treat your condition. Bacterial infections can affect wounds, burns, and organs within the body. They occur when bacteria enter the body that shouldn't. Signs of infection…. Bacterial and viral infections are often transmitted in similar ways, but symptoms and treatment methods may vary depending on the cause of your…. If you're on antibiotics or otherwise sick, you may wonder how to protect those around you from catching what you have.

But are bacterial infections…. Antibiotics are powerful, life-saving medications used to fight infections caused by bacteria. They decrease or kill the growth of bacteria in your…. They cause irritation and…. Viruses, bacteria, fungi, and parasites can all cause skin infections. Infections can range from mild to severe. Learn what to do if you have a skin…. A viral fever is a high body temperature that accompanies many viral infections.

The Supreme Court on Jan. A new study found that 1 in 10 people still had clinically relevant levels of live virus after a day quarantine. This may present a significant…. Viome specializes in gut health testing kits — but do they actually work? Find out everything you need to know and more. Health Conditions Discover Plan Connect. Overview An infection occurs when another organism enters your body and causes disease.

Read this next. Medically reviewed by Gerhard Whitworth, R. Medically reviewed by Dr. Sirisha Yellayi, DO. For You Children Patient Handouts. Start Here. Bacterial vs. Diagnosis and Tests. Prevention and Risk Factors. Related Issues. Clinical Trials.

Article: Investigating host-virus interaction mechanism and phylogenetic analysis of viral proteins involved Viral Infections -- see more articles. Find an Expert. Of the numerous viruses that infect the digestive system, most the enteroviruses and reoviruses are considered to be acute viruses that cause infections even though some may continue to be shed for months or even years. Persistent infections may be caused by hepatitis viruses, adenoviruses, and parvoviruses Table Chronic hepatitis develops in about 10—15 percent of hepatitis B patients.

The presence of viral surface antigen HBsAg or core antigen HbcAG in serum serves as a marker of persistent infection. In chronic infections, HBV productively infects hepatocytes and maintains a low level of virus production over a long period.

Integration is not required for virus replication, but it may be a crucial event for long-term perpetuation of the virus genome. In addition, HBV is capable of causing latent infections e.

The factors that determine the development of chronic infection with HBV have not been fully identified. Immune tolerance to the surface protein of HBV appears to be one of the factors involved in the development of the carrier state. The chronic infection is related to an inefficient T-cell response to viral components critical for protective immunity.

There is strong epidemiological evidence of a causal relationship between persistent HBV infection and development of hepatocellular carcinoma. Individuals who have antibody to hepatitis C should be considered potentially persistently infected, and the presence of viral RNA in infections by hepatitis C are associated with chronic persistent or active hepatitis, cirrhosis, and hepatocellular carcinoma.

The mechanism of this interaction is currently being studied. There is no evidence that hepatitis A or E causes persistent infections. Adenoviruses AdV typically cause acute disease of the respiratory and gastrointestinal tracts of human beings. The high incidence of adenovirus infections in organ transplant kidney, bone marrow recipients and AIDS patients suggests that these infections most probably represent reactivation of a latent adenovirus infection. For example, AdV can persist latently for years in adenoids and tonsils and often are shed in the feces for many months after the initial infection.

The mechanism and the cell type harboring the latent virus in vivo is presently unknown. In vitro studies have shown that the strategies of C-type AdV types AdV2, AdV5 to evade immune recognition involve the e 3 early genomic region. Protein s of the e 3 region alter the expression, post-translational modification and transport of the major histocompatibility complex HLA class I.

In addition, E3 down-regulates the e 1 a gene product, the immunodominant cytotoxic T cell determinant. It is possible that similar mechanisms operate in the host during natural persistent infection. The replication of the simplest DNA viruses, the parvoviruses, is dependent on functions supplied by replicating host cells Parvovirus genus or by coinfection with helper viruses, usually adenovirus Dependovirus genus. Both genuses have been shown to develop persistent infection in humans.

For example, parvovirus B19 infects primarily the erythroid progenitors, causing chronic hemolytic anemia, neutropenia, and persistent arthritis mainly in immunocompromised individuals. The dependovirus group of parvoviruses adeno-associated viruses; AAV can be isolated from fecal, ocular, or respiratory specimens and from penile and condylomatous lesions during simultaneous adenovirus infections.

The AAV integrate into host cell DNA and replicate with it, only to be excised and induced to replicate when the latently infected cells are superinfected with adenoviruses.

The dependoviruses are not known to be pathogenic. Of the viruses that cause acute infections of the skin and mucous membranes, herpesviruses see above and papillomaviruses Table are also capable of establishing persistent infections. The ubiquity of latent papillomavirus infections is emphasized by the frequent, often acute outbreak of warts in immunosuppressed patients and pregnant women.

HPVs specifically infect basal or germ cells of the epidermis. The virus genome persists in episomal form, as a result of the multiple DNA-protein and protein-protein interactions between viral and cellular regulatory factors. In latency, viral DNA replication and transcription are maintained at very low levels and regulated by negative cellular factors e. For example, the viral E1 replication protein functions as an E2 co-repressor when bound to the origin of DNA replication. Productive viral replication occurs only in terminally-differentiated skin cells see Fig.

Where, presumably in response to differentiation-specific signals, viral transcription accelerates, DNA synthesis begins and virions assemble see Ch. Persistent HPV infections are associated with a number of skin and cervical cancers see Ch. Successful medical treatment for persistent or chronic virus infections is presently being developed. Attempts to control latent virus reactivation have included vaccination and treatment with interferon and various antiviral compounds.

For example, experimental vaccines against HSV-1 or -2 may reduce the number of reactivation syndromes, but do not eliminate latent virus. Hepatitis B vaccines significantly reduce the percent of chronic HBV carriers. Interferon reacts with specific receptors, activating cytoplasmic cascades that stimulate cellular genes encoding a number of proteins which lead to the repression of virus e.

Zidovudine AZT , alone or in combination with additional factors e. Also, health education is an important component in preventing the spread of infections that tend to persist. Turn recording back on. National Center for Biotechnology Information , U. Show details Baron S, editor. Search term. General Concepts Definition Persistent infections are characterized as those in which the virus is not cleared but remains in specific cells of infected individuals.

Pathogenesis The mechanisms by which persistent infections are maintained involve both modulation of virus and cellular gene expression and modification of the host immune response. Persistent Infections by Organ System Some viruses can establish persistent infection at the same time in different cell types of one or more tissues or organs.

In Vitro Models of Persistence Three kinds of persistent infection can be maintained in cell cultures: chronic focal, chronic diffuse, and latent. Control No measures to eradicate persistent viruses have been developed.

Classification Persistent infections are those in which the virus is not cleared from the host following primary infection, but remains associated with specific cells. Figure Natural history of acute and persistent human infections. Models of Virus Persistence in Vitro Three types of persistent infection can be distinguished in cultured cells Table Pathogenesis of Persistent Virus Infections Persistent infections are caused by a wide variety of viruses through diverse pathogenetic mechanisms that may cause strikingly different diseases see Chs.

Examples include: 1. Viral antigenic variation e. Compromised nonspecific defenses e. Immune tolerance? Reactivation of Persistent Viruses For disease to recur in a latent infection the virus must be reactivated and begin replicating. Persistent Infections by Organ System Immune System A number of viruses can infect cells of the lymphoid system during acute infection, and some of these viruses persist Table Human T-Cell Leukemia Viruses Infection by these viruses is followed by a to year clinically latent period before development of leukemias or neurologic disorders in a minority of infected individuals.

Human Cytomegalovirus The strongest evidence for the existence of latent CMV infection comes from the increased incidence of reactivated infection in seronegative individuals who undergo transplants of organs from seropositive donors or in immunosuppressed AIDS patients. Nervous System Many chronic, degenerative nervous system diseases are related to viral persistence Table Figure Establishment and reactivation of latent herpesvirus infections.

Varicella-Zoster Virus After recovery from acute varicella chickenpox , the virus establishes latency in multiple ganglia of the human neuraxis Fig.

Measles Virus Measles is normally an acute self-limited disease in which the virus appears to be eliminated. Prions The subacute spongiform virus encephalopathies are a unique type of slow virus infection caused by agents called unconventional viruses or prions see Ch.

Digestive System Of the numerous viruses that infect the digestive system, most the enteroviruses and reoviruses are considered to be acute viruses that cause infections even though some may continue to be shed for months or even years. Adenoviruses Adenoviruses AdV typically cause acute disease of the respiratory and gastrointestinal tracts of human beings.

Parvoviruses The replication of the simplest DNA viruses, the parvoviruses, is dependent on functions supplied by replicating host cells Parvovirus genus or by coinfection with helper viruses, usually adenovirus Dependovirus genus. Skin Of the viruses that cause acute infections of the skin and mucous membranes, herpesviruses see above and papillomaviruses Table are also capable of establishing persistent infections. Human Papillomaviruses The ubiquity of latent papillomavirus infections is emphasized by the frequent, often acute outbreak of warts in immunosuppressed patients and pregnant women.

Control of Persistent Infections Successful medical treatment for persistent or chronic virus infections is presently being developed.

Review: protective efficacy of hepatitis B vaccines in neonates. J Med Virol. Regulation of human immunodeficiency virus infection: implications for pathogenesis. Adv Virus Res. Baron S, Dianzani F. The interferons: a biological system with therapeutic potential in viral infections. Antiviral Res. A molecular mechanism for human T-cell leukemia virus latency and Tax transactivation. J Biol Chem. Gonda MA.