Viruses are among the smallest microbes, typically ranging from 0.02 to 0.3 micrometer, although several very large viruses up to 1 micrometer in length (megavirus, pandoravirus) have recently been discovered. Viruses depend completely on cells (bacterial, plant, or animal) to reproduce. Some viruses have an outer envelope consisting of protein and lipid, surrounding a protein capsid complex with genomic RNA or DNA and sometimes enzymes needed for the first steps of viral replication.
Classification of viruses is principally according to their genome sequence taking into consideration nature and structure of their genome and their method of replication, but not according to the diseases they cause (see International Committee on Taxonomy of Viruses (ICTV), 2021 release). Thus, there are DNA viruses and RNA viruses; either DNA or RNA viruses may have single or double strands of genetic material. Single-strand RNA viruses are further divided into those with (+) sense and (-) sense RNA. Positive-sense RNA viruses possess a single-stranded RNA genome that can serve as messenger RNA (mRNA) that can be directly translated to produce an amino acid sequence. Negative-sense RNA viruses possess a single-stranded negative-sense genome that first must synthesize a complementary positive-sense antigenome, which is then used to make genomic negative-sense RNA. DNA viruses typically replicate in the host cell nucleus, and RNA viruses typically replicate in the cytoplasm.
Certain single-strand, (+) sense RNA viruses termed retroviruses use a very different method of replication. Retroviruses use reverse transcription to create a double-stranded DNA copy (a provirus) of their RNA genome, which is inserted into the genome of their host cell. Reverse transcription is accomplished using the enzyme reverse transcriptase, which the virus carries with it inside its shell. Examples of retroviruses are the human immunodeficiency viruses and the human T-cell leukemia viruses. Once the provirus is integrated into the host cell DNA, it is transcribed using typical cellular mechanisms to produce viral proteins and genetic material.
If a germline cell is infected by a retrovirus, the integrated provirus can become established as an endogenous retrovirus that is transmitted to offspring. The sequencing of the human genome revealed that at least 1% of the human genome consists of endogenous retroviral sequences, representing past encounters with retroviruses during the course of human evolution. A few endogenous human retroviruses have remained transcriptionally active and produce functional proteins (eg, the syncytins that contribute to the structure of the human placenta) (1 References Viruses are among the smallest microbes, typically ranging from 0.02 to 0.3 micrometer, although several very large viruses up to 1 micrometer in length (megavirus, pandoravirus) have recently... read more ). Some experts speculate that some disorders of uncertain etiology, such as multiple sclerosis, certain autoimmune disorders, and various cancers, may be caused by endogenous retroviruses.
Because RNA transcription does not involve the same error-checking mechanisms as DNA transcription, RNA viruses, particularly retroviruses, are particularly prone to mutation.
Viral genomes are small; the genome of RNA viruses ranges from 3.5 kilobases (some retroviruses) to 27 kilobases (some reoviruses), and the genome of DNA viruses ranges from 5 kilobases (some parvoviruses) to 280 kilobases (some poxviruses). This manageable size together with the current advances in nucleotide sequencing technology means that partial and whole virus genome sequencing will become an essential component in epidemiologic investigations of disease outbreaks.
For infection to occur, the virus first attaches to the host cell at one or one of several receptor molecules on the cell surface. The viral DNA or RNA then enters the host cell and separates from the outer cover (uncoating) and replicates inside the host cell in a process that requires specific enzymes. The newly synthesized viral components then assemble into a complete virus particle. The host cell typically dies, releasing new viruses that infect other host cells. Each step of viral replication involves different enzymes and substrates and offers an opportunity to interfere with the process of infection.
The consequences of viral infection vary considerably. Many infections cause acute illness after a brief incubation period, but some are asymptomatic or cause minor symptoms that may not be recognized. Many viral infections are cleared by the immune system, but some remain in a latent state, and some cause chronic disease.
In latent infection, viral RNA or DNA remains in host cells but does not replicate or cause disease for a long time, sometimes for many years. Latent viral infections may be transmissible during the asymptomatic period, facilitating person-to-person spread. Sometimes a trigger (particularly immunosuppression) causes reactivation.
Common viruses that remain latent include
Papovaviruses (composed of 2 subgroups: papilloma and polyoma viruses)
Ebola virus Treatment Marburg and Ebola are filoviruses that cause hemorrhage, multiple organ failure, and high mortality rates. Diagnosis is with enzyme-linked immunosorbent assay, polymerase chain reaction (PCR)... read more appears to persist in the immunologically privileged sites in the human body (eg, testes, eyes) (2 References Viruses are among the smallest microbes, typically ranging from 0.02 to 0.3 micrometer, although several very large viruses up to 1 micrometer in length (megavirus, pandoravirus) have recently... read more ).
Some disorders are caused by viral reactivation in the central nervous system after a very long latency period. These diseases include
Progressive multifocal leukoencephalopathy Progressive Multifocal Leukoencephalopathy (PML) Progressive multifocal leukoencephalopathy (PML) is caused by reactivation of the JC virus. The disease usually occurs in patients with impaired cell-mediated immunity, particularly patients... read more
(due to the JC [John Cunningham] virus, a polyomavirus)
Subacute sclerosing panencephalitis Subacute Sclerosing Panencephalitis (SSPE) Subacute sclerosing panencephalitis is a progressive, usually fatal brain disorder occurring months to usually years after an attack of measles. It causes mental deterioration, myoclonic jerks... read more (due to measles virus)
Progressive rubella panencephalitis Progressive Rubella Panencephalitis Progressive rubella panencephalitis is a neurologic disorder occurring in children with congenital rubella. It is presumably due to persistence or reactivation of rubella virus infection. Congenital... read more (due to rubella virus)
Chronic viral infections are characterized by continuous, prolonged viral shedding; examples are congenital infection with rubella virus Congenital Rubella Congenital rubella is a viral infection acquired from the mother during pregnancy. Signs are multiple congenital anomalies that can result in fetal death. Diagnosis is by serology and viral... read more or with cytomegalovirus Congenital and Perinatal Cytomegalovirus Infection (CMV) Cytomegalovirus infection may be acquired prenatally or perinatally and is the most common congenital viral infection. Signs at birth, if present, are intrauterine growth restriction, prematurity... read more and persistent hepatitis B Hepatitis B, Chronic Hepatitis B is a common cause of chronic hepatitis. Patients may be asymptomatic or have nonspecific manifestations such as fatigue and malaise. Diagnosis is by serologic testing. Without treatment... read more or C Hepatitis C, Chronic Hepatitis C is a common cause of chronic hepatitis. It is often asymptomatic until manifestations of chronic liver disease occur. Diagnosis is confirmed by finding positive anti-HCV and positive... read more . HIV Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more
can cause both latent and chronic infections.
Several hundred different viruses infect humans. Viruses that infect primarily humans often spread via respiratory and enteric excretions. Blood that is collected for transfusion is tested for a number of viruses (see table ). Many viruses are transmitted via rodent or arthropod vectors, and bats have recently been identified as hosts for many mammalian viruses, including some responsible for certain serious human infections (eg, SARS-CoV-2 COVID-19 COVID-19 is an acute, sometimes severe, respiratory illness caused by the novel coronavirus SARS-CoV-2. Prevention is by vaccination and infection control precautions (eg, face masks, handwashing... read more ).
Some viruses are transmitted sexually via mucosal contact, such as Zika Zika Virus (ZV) Infections The Zika virus is a mosquito-borne flavivirus that is antigenically and structurally similar to the viruses that cause dengue, yellow fever, and West Nile virus. Zika virus infection is typically... read more . Other viruses are transmitted through transfer of blood (eg, through puncture by a contaminated needle, or transfusion), including hepatitis viruses A Hepatitis A Hepatitis A is caused by an enterically transmitted RNA virus that, in older children and adults, causes typical symptoms of viral hepatitis, including anorexia, malaise, and jaundice. Young... read more , B Hepatitis B, Chronic Hepatitis B is a common cause of chronic hepatitis. Patients may be asymptomatic or have nonspecific manifestations such as fatigue and malaise. Diagnosis is by serologic testing. Without treatment... read more , C Hepatitis C, Chronic Hepatitis C is a common cause of chronic hepatitis. It is often asymptomatic until manifestations of chronic liver disease occur. Diagnosis is confirmed by finding positive anti-HCV and positive... read more , and E Hepatitis E Hepatitis E is caused by an enterically transmitted RNA virus and causes typical symptoms of viral hepatitis, including anorexia, malaise, and jaundice. Fulminant hepatitis and death are rare... read more , and the following arboviruses:
Cytomegalovirus [CMV] Cytomegalovirus (CMV) Infection Cytomegalovirus (CMV, human herpesvirus type 5) can cause infections that have a wide range of severity. A syndrome of infectious mononucleosis that lacks severe pharyngitis is common. Severe... read more and Epstein–Barr virus Infectious Mononucleosis Infectious mononucleosis is caused by Epstein-Barr virus (EBV, human herpesvirus type 4) and is characterized by fatigue, fever, pharyngitis, and lymphadenopathy. Fatigue may persist weeks or... read more are the viruses most predominantly transferred through transplantation of tissue. Other such viruses include
Arboviruses such as Zika Zika Virus (ZV) Infections The Zika virus is a mosquito-borne flavivirus that is antigenically and structurally similar to the viruses that cause dengue, yellow fever, and West Nile virus. Zika virus infection is typically... read more , West Nile West Nile Virus West Nile virus is a flavivirus that is now the primary cause of arbovirus encephalitis in the United States. Most patients have mild or no symptoms. About 1 out of 150 patients develop a severe... read more , and dengue Dengue Dengue is a mosquito-borne disease caused by a flavivirus. Dengue fever usually results in abrupt onset of high fever, headache, myalgias, arthralgias, and generalized lymphadenopathy, followed... read more
Viruses exist worldwide, but their spread is limited by inborn resistance, prior immunizing infections or vaccines, sanitary and other public health control measures, and prophylactic antiviral drugs.
Zoonotic viruses Overview of Arbovirus, Arenavirus, and Filovirus Infections Arbovirus (arthropod-borne virus) is defined as any virus that is transmitted to humans and/or other vertebrates by certain species of blood-feeding arthropods, mostly insects (flies and mosquitoes)... read more pursue their biologic cycles chiefly in animals; humans are secondary or accidental hosts. These viruses are limited to areas and environments able to support their nonhuman natural cycles of infection (vertebrates, arthropods, or both).
Variant Creutzfeldt-Jakob disease Variant CJD (vCJD) Creutzfeldt-Jakob disease (CJD) is the most common human prion disease. It occurs worldwide and has several forms and subtypes. CJD symptoms include dementia, myoclonus, and other central nervous... read more and bovine spongiform encephalopathy were initially thought to be caused by a virus and termed slow viral diseases because they have lengthy incubations (years), but they are now known to be caused by prions Overview of Prion Diseases Prion diseases are progressive, fatal, and untreatable degenerative brain disorders. Prominent types of prion diseases include Creutzfeldt-Jakob disease (CJD), the prototypic example (usually... read more ; prions are proteinaceous disease-causing agents that are not bacterial, fungal, or viral and that contain no genetic material.
(See also Types of Viral Disorders Types of Viral Disorders Categorizing viral infections by the organ system most commonly affected (eg, lungs, gastrointestinal tract, skin, liver, central nervous system, mucous membranes) can be clinically useful,... read more .)
Viruses and cancer
Some viruses are oncogenic and predispose to certain cancers:
Human immunodeficiency virus (HIV) Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more
: Kaposi sarcoma Kaposi Sarcoma Kaposi sarcoma is a multicentric vascular tumor caused by herpesvirus type 8. It can occur in classic, AIDS-associated, endemic (in Africa), and iatrogenic (eg, after organ transplantation)... read more
, non-Hodgkin lymphoma Non-Hodgkin Lymphomas Non-Hodgkin lymphomas are a heterogeneous group of disorders involving malignant monoclonal proliferation of lymphoid cells in lymphoreticular sites, including lymph nodes, bone marrow, the... read more
, cervical carcinoma Cervical Cancer Cervical cancer is usually a squamous cell carcinoma; less often, it is an adenocarcinoma. The cause of most cervical cancers is human papillomavirus infection. Cervical neoplasia is often asymptomatic... read more
, Hodgkin lymphoma Hodgkin Lymphoma Hodgkin lymphoma is a localized or disseminated malignant proliferation of cells of the lymphoreticular system, primarily involving lymph node tissue, spleen, liver, and bone marrow. Symptoms... read more
, and carcinomas of the mouth Overview of Head and Neck Tumors Head and neck cancer develops in almost 65,000 people in the United States each year. Excluding skin and thyroid cancers, > 90% of head and neck cancers are squamous cell (epidermoid) carcinomas... read more , throat Overview of Head and Neck Tumors Head and neck cancer develops in almost 65,000 people in the United States each year. Excluding skin and thyroid cancers, > 90% of head and neck cancers are squamous cell (epidermoid) carcinomas... read more , liver Primary Liver Cancer Primary liver cancer is usually hepatocellular carcinoma (HCC). The first manifestations of liver cancer are usually nonspecific, delaying the diagnosis. When diagnosed at advanced stages, prognosis... read more , lung Lung Carcinoma Lung carcinoma is the leading cause of cancer-related death in men and women worldwide. About 85% of cases are related to cigarette smoking. Symptoms can include cough, chest discomfort or pain... read more
, and anus Anal Cancer Anal cancer accounts for an estimated 8590 cases and about 1350 deaths in the US annually ( 1). The main symptom is bleeding with defecation. Diagnosis is by endoscopy. Treatment options include... read more
Human papillomavirus Human Papillomavirus (HPV) Infection Human papillomavirus (HPV) infects epithelial cells. Most of the > 100 subtypes infect cutaneous epithelium and cause skin warts; some types infect mucosal epithelium and cause anogenital warts... read more
(HPV): Cervical carcinoma Cervical Cancer Cervical cancer is usually a squamous cell carcinoma; less often, it is an adenocarcinoma. The cause of most cervical cancers is human papillomavirus infection. Cervical neoplasia is often asymptomatic... read more
, penile carcinoma Penile Cancer Most penile cancers are squamous cell carcinomas; they usually occur in uncircumcised men, particularly those with poor local hygiene. Diagnosis is by biopsy. Treatment includes excision. Penile... read more
, vaginal carcinoma Vaginal Cancer Vaginal cancer is usually a squamous cell carcinoma, most often occurring in women > 60. The most common symptom is abnormal vaginal bleeding. Diagnosis is by biopsy. Treatment for many small... read more , anal carcinoma Anal Cancer Anal cancer accounts for an estimated 8590 cases and about 1350 deaths in the US annually ( 1). The main symptom is bleeding with defecation. Diagnosis is by endoscopy. Treatment options include... read more
, oropharyngeal carcinoma Oropharyngeal Squamous Cell Carcinoma Oropharyngeal cancer refers to cancer of the tonsil, base and posterior one third of the tongue, soft palate, and posterior and lateral pharyngeal walls. Squamous cell carcinoma comprises over... read more , and esophageal carcinoma Esophageal Cancer The most common malignant tumor in the proximal two thirds of the esophagus is squamous cell carcinoma; adenocarcinoma is the most common in the distal one third. Symptoms are progressive dysphagia... read more
Human T-lymphotropic virus 1 Human Immunodeficiency Virus (HIV) Infection
: Certain types of human leukemia and lymphoma
Epstein-Barr virus Infectious Mononucleosis Infectious mononucleosis is caused by Epstein-Barr virus (EBV, human herpesvirus type 4) and is characterized by fatigue, fever, pharyngitis, and lymphadenopathy. Fatigue may persist weeks or... read more
: Nasopharyngeal carcinoma Nasopharyngeal Cancer Squamous cell carcinoma is the most common cancer of the nasopharynx. Symptoms develop late, including unilateral bloody nasal discharge, nasal obstruction, hearing loss, ear pain, facial swelling... read more , Burkitt lymphoma Burkitt Lymphoma Burkitt lymphoma is an aggressive B-cell non-Hodgkin lymphoma occurring in children and adults. Endemic (African), sporadic (non-African), and immunodeficiency-related forms exist. (See also... read more
, Hodgkin lymphoma Hodgkin Lymphoma Hodgkin lymphoma is a localized or disseminated malignant proliferation of cells of the lymphoreticular system, primarily involving lymph node tissue, spleen, liver, and bone marrow. Symptoms... read more
, and lymphomas in immunosuppressed organ transplant recipients
Hepatitis B Hepatitis B, Acute Hepatitis B is caused by a DNA virus that is often parenterally transmitted. It causes typical symptoms of viral hepatitis, including anorexia, malaise, and jaundice. Fulminant hepatitis and... read more and hepatitis C Hepatitis C, Acute Hepatitis C is caused by an RNA virus that is often parenterally transmitted. It sometimes causes typical symptoms of viral hepatitis, including anorexia, malaise, and jaundice but may be asymptomatic... read more viruses: Hepatocellular carcinoma Hepatocellular Carcinoma Hepatocellular carcinoma (HCC) usually occurs in patients with cirrhosis and is common in areas where infection with hepatitis B and C viruses is prevalent. Symptoms and signs are usually nonspecific... read more
Human herpesvirus 8 Overview of Herpesvirus Infections Eight types of herpesviruses infect humans ( see Table: Herpesviruses That Infect Humans). After initial infection, all herpesviruses remain latent within specific host cells and may subsequently... read more : Kaposi sarcoma Kaposi Sarcoma Kaposi sarcoma is a multicentric vascular tumor caused by herpesvirus type 8. It can occur in classic, AIDS-associated, endemic (in Africa), and iatrogenic (eg, after organ transplantation)... read more
, primary effusion lymphomas, and multicentric Castleman disease (a lymphoproliferative disorder)
References
1. Dupressoir A, Lavialle C, Heidmann T: From ancestral infectious retroviruses to bona fide cellular genes: role of the captured syncytins in placentation. Placenta 33(9):663-671, 2012. doi:10.1016/j.placenta.2012.05.005
2. Schindell BG, Webb AL, Kindrachuk J: Persistence and sexual transmission of filoviruses. Viruses 10(12):683, 2018. doi: 10.3390/v10120683
Diagnosis of Viral Infections
Some viral disorders can be diagnosed as follows:
Clinically (ie, diagnosis based on well-known patient symptoms, eg, measles Measles Measles is a highly contagious viral infection that is most common among children. It is characterized by fever, cough, coryza, conjunctivitis, an enanthem (Koplik spots) on the oral mucosa... read more
, rubella Rubella (See also Congenital Rubella.) Rubella is a viral infection that may cause adenopathy, rash, and sometimes constitutional symptoms, which are usually mild and brief. Infection during early pregnancy... read more
, roseola infantum Roseola Infantum Roseola infantum is an infection of infants or very young children caused by human herpesvirus 6B (HHV-6B) or, less commonly, HHV-7. The infection causes high fever and a rubelliform eruption... read more
, erythema infectiosum Erythema Infectiosum (Parvovirus B19 Infection) Erythema infectiosum is caused by acute infection with human parvovirus B19. In children, it causes mild constitutional symptoms and a blotchy or maculopapular rash beginning on the cheeks and... read more
, and chickenpox Chickenpox Chickenpox is an acute, systemic, usually childhood infection caused by the varicella-zoster virus (human herpesvirus type 3). It usually begins with mild constitutional symptoms that are followed... read more
)
Epidemiologically (ie, diagnosis based on case definition during epidemic outbreaks, eg, influenza Influenza Influenza is a viral respiratory infection causing fever, coryza, cough, headache, and malaise. Mortality is possible during seasonal epidemics, particularly among high-risk patients (eg, those... read more , norovirus Norovirus Gastroenteritis Norovirus is a common cause of diarrhea. Symptoms are vomiting, abdominal cramps, and diarrhea that usually resolve in 1 to 3 days. Diagnosis is based on clinical suspicion, and polymerase chain... read more , and mumps Mumps Mumps is an acute, contagious, systemic viral disease, usually causing painful enlargement of the salivary glands, most commonly the parotids. Complications may include orchitis, meningoencephalitis... read more
)
Definitive laboratory diagnosis is necessary mainly when specific treatment may be helpful or when the agent may be a public health threat (eg, HIV). Most hospital laboratories can test for many viruses, but for less common disorders (eg, rabies Rabies Rabies is a viral encephalitis transmitted by the saliva of infected bats and certain other infected mammals. Symptoms include depression and fever, followed by agitation, excessive salivation... read more , Eastern equine encephalitis, human parvovirus B19), specimens must be sent to state health laboratories or the Centers for Disease Control and Prevention.
Serologic examination for antibodies during acute and convalescent stages can be sensitive and specific, but slow; with some viruses, especially flaviviruses, cross-reactions confound diagnosis. More rapid diagnosis can sometimes be made using culture, polymerase chain reaction, or viral antigen tests. Histopathology with electron (not light) microscopy can sometimes help. For specific diagnostic procedures, see Laboratory Diagnosis of Infectious Disease Introduction to Laboratory Diagnosis of Infectious Disease Laboratory tests may identify organisms directly (eg, visually, using a microscope, growing the organism in culture) or indirectly (eg, identifying antibodies to the organism). General types... read more .
Treatment of Viral Infections
Antiviral drugs
Progress in the use of antiviral drugs is occurring rapidly. Mechanisms of antiviral drugs can be directed at various phases of viral replication. They can
Interfere with viral particle attachment to host cell membranes or uncoating of viral nucleic acids
Inhibit a cellular receptor or factor required for viral replication
Block specific virus-encoded enzymes and proteins that are produced in the host cells and that are essential for viral replication but not for normal host cell metabolism
Antiviral drugs are most often used therapeutically or prophylactically against herpesviruses Overview of Herpesvirus Infections Eight types of herpesviruses infect humans ( see Table: Herpesviruses That Infect Humans). After initial infection, all herpesviruses remain latent within specific host cells and may subsequently... read more (including cytomegalovirus Cytomegalovirus (CMV) Infection Cytomegalovirus (CMV, human herpesvirus type 5) can cause infections that have a wide range of severity. A syndrome of infectious mononucleosis that lacks severe pharyngitis is common. Severe... read more ), respiratory viruses Overview of Viral Respiratory Infections Viral infections commonly affect the upper or lower respiratory tract. Although respiratory infections can be classified by the causative virus (eg, influenza), they are generally classified... read more , HIV Human Immunodeficiency Virus (HIV) Infection Human immunodeficiency virus (HIV) infection results from 1 of 2 similar retroviruses (HIV-1 and HIV-2) that destroy CD4+ lymphocytes and impair cell-mediated immunity, increasing risk of certain... read more , chronic hepatitis B Hepatitis B, Chronic Hepatitis B is a common cause of chronic hepatitis. Patients may be asymptomatic or have nonspecific manifestations such as fatigue and malaise. Diagnosis is by serologic testing. Without treatment... read more , and chronic hepatitis C Hepatitis C, Chronic Hepatitis C is a common cause of chronic hepatitis. It is often asymptomatic until manifestations of chronic liver disease occur. Diagnosis is confirmed by finding positive anti-HCV and positive... read more . However, some drugs are effective against many different kinds of viruses. For example, some drugs active against HIV are used for other viral infections such as hepatitis B.
Antiviral drugs have been developed for treatment of COVID-19 COVID-19 COVID-19 is an acute, sometimes severe, respiratory illness caused by the novel coronavirus SARS-CoV-2. Prevention is by vaccination and infection control precautions (eg, face masks, handwashing... read more , which is caused by SARS-CoV-2.
Interferons
Interferons are compounds released from infected host cells in response to viral or other foreign antigens.
There are many different interferons, which have numerous effects such as blocking translation and transcription of viral RNA and stopping viral replication without disturbing normal host cell function.
Interferons are sometimes given attached to polyethylene glycol (pegylated formulations), allowing slow, sustained release of the interferon.
Viral disorders sometimes treated with interferon therapy include
Chronic hepatitis B Hepatitis B, Chronic Hepatitis B is a common cause of chronic hepatitis. Patients may be asymptomatic or have nonspecific manifestations such as fatigue and malaise. Diagnosis is by serologic testing. Without treatment... read more and chronic hepatitis C Hepatitis C, Chronic Hepatitis C is a common cause of chronic hepatitis. It is often asymptomatic until manifestations of chronic liver disease occur. Diagnosis is confirmed by finding positive anti-HCV and positive... read more
Adverse effects of interferons include fever, chills, weakness, and myalgia, typically starting 7 to 12 hours after the first injection and lasting up to 12 hours. Depression, hepatitis, and, when high doses are used, bone marrow suppression are also possible.
Antibodies
Convalescent serum and monoclonal antibodies Monoclonal antibodies Immunotherapeutic agents use or modify immune mechanisms. Use of these agents is rapidly evolving; new classes, new agents, and new uses of current agents are certain to be developed. A number... read more (mAbs) can be used to treat some viral infections (eg, Zaire Ebola virus infection Ebola Vaccine rVSV-ZEBOV is the only vaccine approved by the U.S. Food and Drug Administration (FDA) for prevention of Ebola virus disease. Ad26.ZEBOV/MVA-BN-Filo is a combination of two vaccines, Ad26.ZEBOV... read more , respiratory syncytial virus [RSV], rabies virus).
Prevention of Viral Infections
Vaccines
Vaccines Overview of Immunization work by stimulating immunity. Viral vaccines in general use include vaccines for
Japanese encephalitis
Tick-borne encephalitis
Adenovirus, smallpox Prevention Smallpox is a highly contagious disease caused by the smallpox virus, an orthopoxvirus. Case fatality rate is about 30%. Natural infection has been eradicated. The main concern for outbreaks... read more , and mpox Mpox (Monkeypox) Mpox (monkeypox)is caused by the monkeypox virus, an orthopoxvirus structurally related to the smallpox virus. Patients present with a vesicular or pustular rash that may be painful and... read more
vaccines, as well as Rift Valley fever Rift Valley fever Arbovirus (arthropod-borne virus) applies to any virus that is transmitted to humans and/or other vertebrates by certain species of blood-feeding arthropods, chiefly insects (flies and mosquitoes)... read more and eastern equine encephalitis Encephalitis Encephalitis is inflammation of the parenchyma of the brain, resulting from direct viral invasion or occurring as a postinfectious immunologic complication caused by a hypersensitivity reaction... read more vaccines are available but used only in high-risk groups (eg, military recruits).
Multiple vaccines for prevention of COVID-19 COVID-19 Vaccine COVID-19 vaccines provide protection against COVID-19, the disease caused by infection with the SARS-CoV-2 virus. Vaccination is the most effective strategy to prevent severe illness and death... read more , caused by SARS-CoV-2, have been developed, including mRNA and other types of vaccines.
Viral diseases can be eradicated by effective vaccines. Smallpox was eradicated in 1978, and the cattle plague rinderpest (caused by a virus closely related to human measles virus) was eradicated in 2011. Extensive vaccination has almost eradicated polio Poliomyelitis Vaccine Extensive vaccination has almost eradicated polio worldwide. But cases still occur in areas with incomplete immunization, such as sub-Saharan Africa and southern Asia. There are 3 serotypes... read more worldwide, but cases still occur in areas with incomplete immunization, such as sub-Saharan Africa and southern Asia. Measles has been almost eradicated from some parts of the world, notably the Americas, but because measles is highly contagious and vaccination coverage is incomplete, even in regions where it is considered eradicated, final eradication is not imminent.
The prospects for development of vaccines and eradication of other more intractable virus infections (such as HIV) are presently uncertain.
Immune globulins
Immune globulins Passive Immunization Passive immunization involves giving antibodies to an organism or to a toxin produced by an organism. Passive immunization is provided in the following circumstances: When people cannot synthesize... read more are available for passive immune prophylaxis in limited situations. They can be used preexposure (eg, for hepatitis A), postexposure (eg, for rabies, varicella, respiratory syncytial virus, hepatitis), and for treating disease (eg, eczema vaccinatum).
Protective measures
Many viral infections can be prevented by routine protective measures (which vary depending on the transmission mode of a given agent).
Important measures include
Hand washing
Appropriate food preparation and water treatment
Avoidance of contact with sick people
Safer-sex practices
Mask wearing
Physical distancing when appropriate (eg, for COVID-19 prevention)
For infections with an insect vector (eg, mosquitoes, ticks), personal protection against vector bites is important, such as repellents, proper clothing.
For infections such as Ebola virus infection Ebola Vaccine rVSV-ZEBOV is the only vaccine approved by the U.S. Food and Drug Administration (FDA) for prevention of Ebola virus disease. Ad26.ZEBOV/MVA-BN-Filo is a combination of two vaccines, Ad26.ZEBOV... read more , avoiding contact with blood and body fluids (such as urine, feces, saliva, sweat, vomit, breast milk, amniotic fluid, semen, and vaginal fluids) of people who are sick is an important protective measure. Contact with semen from a man who has recovered from Ebola virus infection should be avoided until testing shows that the virus is gone from his semen.
Drugs Mentioned In This Article
Drug Name | Select Trade |
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polyethylene glycol |
GaviLax, GIALAX , GlycoLax, Healthylax, MiraLax, Visine Dry Eye Relief, Vita Health |