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Viral infections

A viral disease, or viral infection, occurs when an organism’s body is invaded by pathogenic viruses.

The infectious virus particles, virions, attach to and enter susceptible cells.

Virus species within the same family generally share the same features:

Basic structural characteristics, such as genome type, virion shape and replication site.

Double-stranded DNA families: three are non-enveloped: Adenoviridae, Papillomaviridae and Polyomaviridae, and two are enveloped:Herpesviridae and Poxviridae.

All non-enveloped families have icosahedral nucleotide capsids.

Partly double-stranded DNA viruses: Hepadnaviridae :are enveloped.

One family of single-stranded DNA viruses infects humans: Parvoviridae. 

These viruses are non-enveloped.

Positive single-stranded RNA families: three non-enveloped Astroviridae, Caliciviridae and Picornaviridae and four enveloped Coronaviridae, Flaviviridae, Retroviridae and Togaviridae.

Negative single-stranded RNA families: Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, ParamyxoviridaeParamyxoviridae and Rhabdoviridae. All are enveloped with helical nucleocapsids.

Double-stranded RNA genome: Reoviridae.

The Hepatitis D virus has not yet been assigned to a family, but is clearly distinct from the other families infecting humans.

Viruses infect humans and not be associated with disease: that have Anelloviridae and the genus Dependovirus are non-enveloped single-stranded DNA viruses.

As a general rule, DNA viruses replicate within the cell nucleus while RNA viruses replicate within the cytoplasm: Exceptions, poxviruses replicate within the cytoplasm and orthomyxoviruses and hepatitis D virus (RNA viruses) replicate within the nucleus.

Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae are all RNA viruses.

The Viruses transmitted almost exclusively by arthropods: Bunyavirus, Flavivirus, and Togavirus. 

Some Reoviruses are transmitted from arthropod vectors, and al all are RNA viruses.

One family of enveloped viruses causes gastroenteritis-Coronaviridae.

All other viruses associated with gastroenteritis are non-enveloped.

Categories of virus by groups:

I – dsDNA

II – ssDNA

III – dsRNA

IV – positive-sense ssRNA

V – negative-sense ssRNA

VI – ssRNA-RT

VII – dsDNA-RT

Clinically important virus families and species with characteristics

Family

Baltimore group Important species

Adenoviridae=Adenovirus

Herpesviridae I-Herpes simplex, type 1, Herpes simplex, type 2, Varicella-zoster virus, Epstein–Barr virus, Human cytomegalovirus, Human herpesvirus, type 8

Papillomaviridae Human papillomavirus

Polyomaviridae-BK virus, JC virus N

Poxviridae Smallpox, Monkey pox

Parvoviridae-Parvovirus B19

ReoviridaeIII-Rotavirus, Orbivirus, Coltivirus, Banna virus

AstroviridaeIV-Human astrovirus

Caliciviridae IV Norwalk virus

Coronaviridae IV-Human coronavirus 229E, Human coronavirus NL63, Human coronavirus OC43, Human coronavirus HKU1, Middle East respiratory syndrome-related coronavirus, Severe acute respiratory syndrome coronavirus,Severe acute respiratory syndrome coronavirus 2, COVID-19

Flaviviridae IV-Hepatitis C virus, yellow fever virus, dengue virus,[West Nile virus, TBE virus, Zika virus

Hepeviridae IV Hepatitis E virus

 

Matonaviridae IV  Rubella virus

Picornaviridae IV-coxsackievirus, hepatitis A virus, poliovirus,rhinovirus

Arenaviridae V Lassa virus

Bunyaviridae V Crimean-Congo hemorrhagic fever virus, Hantaan virus

FiloviridaeV Ebola virus,Marburg virus

Orthomyxoviridae V Influenza virus

ParamyxoviridaeV Measles virus, Mumps virus,Parainfluenza virus

PneumoviridaeV Respiratory syncytial virus

RhabdoviridaeV Rabies virus

Unassigned V Hepatitis D

Retroviridae VI HIV

Hepadnaviridae VII Hepatitis B virus

The clinical manifestations  of viruses differ substantially among species within the same family:

 

Reactivation of latent viruses common cause of infections in hematopoietic stem cell transplant patients, such as herpes simplex virus types 1 and 2, vermicelli zoster virus and cytomegalovirus.

Viroporins are small, highly hydrophobic proteins derived from viruses, which interact with membranes to modify the host cell’s permeability to ions or other small molecules.

Several viroporins are observed to localize to the Golgi apparatus and other cytoplasmic structures during viral infection.

CMV infections common among the most common viral infections in the immunocompromised host.

Viruses infect living cells and co-opt the host replication process to produce viral progeny that infects other cells.

For viruses to thrive they must overcome the regulatory components of the cell cycle and avoid a apptosis and the hosts immune surveillance.

Chronic infections are associated with the development of several types of cancer.

Virus- associated malignant tumors account for 10 to 15% of all human cancers worldwide.

A viral disease, or viral infection, occurs when an organism’s body is invaded by pathogenic viruses.

The infectious virus particles, virions, attach to and enter susceptible cells.

Virus species within the same family generally share the same features:

Basic structural characteristics, such as genome type, virion shape and replication site.

Double-stranded DNA families: three are non-enveloped: Adenoviridae, Papillomaviridae and Polyomaviridae, and two are enveloped:Herpesviridae and Poxviridae.

All non-enveloped families have icosahedral nucleotide capsids.

Partly double-stranded DNA viruses: Hepadnaviridae :are enveloped.

One family of single-stranded DNA viruses infects humans: Parvoviridae. 

These viruses are non-enveloped.

Positive single-stranded RNA families: three non-enveloped Astroviridae, Caliciviridae and Picornaviridae and four enveloped Coronaviridae, Flaviviridae, Retroviridae and Togaviridae.

Negative single-stranded RNA families: Arenaviridae, Bunyaviridae, Filoviridae, Orthomyxoviridae, ParamyxoviridaeParamyxoviridae and Rhabdoviridae. All are enveloped with helical nucleocapsids.

Double-stranded RNA genome: Reoviridae.

The Hepatitis D virus has not yet been assigned to a family, but is clearly distinct from the other families infecting humans.

Viruses infect humans and not be associated with disease: that have Anelloviridae and the genus Dependovirus are non-enveloped single-stranded DNA viruses.

As a general rule, DNA viruses replicate within the cell nucleus while RNA viruses replicate within the cytoplasm: Exceptions, poxviruses replicate within the cytoplasm and orthomyxoviruses and hepatitis D virus (RNA viruses) replicate within the nucleus.

Bunyaviridae, Orthomyxoviridae, Arenaviridae, and Reoviridae are all RNA viruses.

The Viruses transmitted almost exclusively by arthropods: Bunyavirus, Flavivirus, and Togavirus. 

Some Reoviruses are transmitted from arthropod vectors, and al all are RNA viruses.

One family of enveloped viruses causes gastroenteritis-Coronaviridae.

All other viruses associated with gastroenteritis are non-enveloped.

Categories of virus by groups:

I – dsDNA

II – ssDNA

III – dsRNA

IV – positive-sense ssRNA

V – negative-sense ssRNA

VI – ssRNA-RT

VII – dsDNA-RT

Clinically important virus families and species with characteristics

Family

Baltimore group Important species

Adenoviridae=Adenovirus

Herpesviridae I-Herpes simplex, type 1, Herpes simplex, type 2, Varicella-zoster virus, Epstein–Barr virus, Human cytomegalovirus, Human herpesvirus, type 8

Papillomaviridae Human papillomavirus

Polyomaviridae-BK virus, JC virus N

Poxviridae Smallpox, Monkey pox

Parvoviridae-Parvovirus B19

ReoviridaeIII-Rotavirus, Orbivirus, Coltivirus, Banna virus

AstroviridaeIV-Human astrovirus

Caliciviridae IV Norwalk virus

Coronaviridae IV-Human coronavirus 229E, Human coronavirus NL63, Human coronavirus OC43, Human coronavirus HKU1, Middle East respiratory syndrome-related coronavirus, Severe acute respiratory syndrome coronavirus,Severe acute respiratory syndrome coronavirus 2, COVID-19

Flaviviridae IV-Hepatitis C virus, yellow fever virus, dengue virus,[West Nile virus, TBE virus, Zika virus

Hepeviridae IV Hepatitis E virus

Matonaviridae IV  Rubella virus

Picornaviridae IV-coxsackievirus, hepatitis A virus, poliovirus,rhinovirus

Arenaviridae V Lassa virus

Bunyaviridae V Crimean-Congo hemorrhagic fever virus, Hantaan virus

FiloviridaeV Ebola virus,Marburg virus

Orthomyxoviridae V Influenza virus

ParamyxoviridaeV Measles virus, Mumps virus,Parainfluenza virus

PneumoviridaeV Respiratory syncytial virus

RhabdoviridaeV Rabies virus

Unassigned V Hepatitis D

Retroviridae VI HIV

Hepadnaviridae VII Hepatitis B virus

The clinical manifestations  of viruses differ substantially among species within the same family:

Type Family Transmission Diseases Treatment Prevention

Adenovirus

droplet contact transmission

fecal-oral

venereal

direct eye contact

gastroenteritis

keratoconjunctivitis

pharyngitis

pharyngoconjunctival fever

Prevention

Adenovirus vaccine

hand washing

covering mouth when coughing or sneezing

avoiding close contact with the sick

CoxsackievirusPicornaviridae

fecal-oral

respiratory droplet contact

Hand, foot and mouth disease

pleurodynia

aseptic meningitis

pericarditis

myocarditis

Prevention CoxsackievirusPicornaviridae

None

hand washing

covering mouth when coughing/sneezing

avoiding contaminated food/water

improved sanitation

CytomegalovirusHerpesviridae

vertical transmission

bodily fluids

infectious mononucleosis

Cytomegalic inclusion disease

Premature birth

liver, lung and spleen diseases in the newborn

Small size at birth

Small head size

congenital seizures in the newborn

Treatment

ganciclovir

cidofovir

foscarnet

Prevention

hand washing

avoid sharing food and drinks with others

safe sex

Epstein–Barr virusHerpesviridae

saliva

infectious mononucleosis

Burkitt’s lymphoma

Hodgkin’s lymphoma

nasopharyngeal carcinoma

Prevention-avoiding close contact with the sick

Hepatitis A virusPicornaviridae

fecal-oral transmission

acute hepatitis

Immunoglobulin (post-exposure prophylaxis)

Hepatitis A vaccine

avoiding contaminated food/water

improved sanitation

Hepatitis B virusHepadnaviridae

Transmitted by bodily fluids

Vertical and sexual transmission

acute hepatitis

chronic hepatitis

hepatic cirrhosis

hepatocellular carcinoma

Lamivudine therapy

immunoglobulins

Adefovir

Entecavir 

Pegylated interferon alfa

Hepatitis B vaccine

immunoglobulin (perinatal and post-exposure prophylaxis)

avoiding shared needles/syringes

safe sex

Hepatitis C virusFlaviviridae

blood

sexual contact

acute hepatitis

chronic hepatitis

hepatic cirrhosis

hepatocellular carcinoma

Ribavirin

Pegylated interferon alfa

avoiding shared needles/syringes

safe sex

Herpes simplex virus, type 1Herpesviridae

direct contact

saliva

herpes labialis, cold sores– can recur by latency

gingivostomatitis in children

tonsillitis & pharyngitis in adults

keratoconjunctivitis

acyclovir

famciclovir

foscarnet

penciclovir

avoiding close contact with lesions

safe sex

Herpes simplex virus, type 2Herpesviridae

sexual contact

vertical transmission

Skin vesicles, mucosal ulcers, Oral and/or genital

Can be latent

Aseptic meningitis

acyclovir

famciclovir

foscarnet

penciclovir

cidofovir

avoiding close contact with lesions

safe sex

HIVRetroviridae

sexual contact

blood

breast milk

vertical transmission

AIDS

HAART,such as protease inhibitors and reverse-transcriptase inhibitors 

zidovudine (perinatally)

blood product screening

safe sex

avoiding shared needles/syringes

Human coronavirus 229E 

droplet contact

fomites

common cold

pneumonia

bronchiolitis

Human coronavirus 

Coronaviridae

droplet contact

common cold

rhinitis

bronchitis

bronchiolitis

pneumonia

croup

Human coronavirus 

Human herpesvirus, type 8Herpesviridae

Saliva

Sexual

Kaposi sarcoma

multicentric Castleman disease

primary effusion lymphoma

many in evaluation-stage

avoid close contact with lesions

safe sex

Human papillomavirusPapillomaviridae

direct contact

sexual contact

vertical transmission

(common, flat, plantar and anogenital warts, laryngeal papillomas, epidermodysplasia verruciformis)

Malignancies (cervical carcinoma,squamous cell carcinomas)

liquid nitrogen

laser vaporization

cytotoxic chemicals

interferon

cidofovir

HPV vaccine

avoiding close contact with lesions

safe sex

Influenza virusOrthomyxoviridae

droplet contact

influenza

Reye syndrome

amantadine

rimantadine

zanamivir

oseltamivir

influenza vaccine

amantadine

rimantadine

hand washing

covering mouth when coughing/sneezing

avoiding close contact with the sick

Measles virusParamyxoviridae

droplet contact

measles

postinfectious encephalomyelitis

MMR vaccine

quarantining the sick

avoiding contact with the sick

Middle East respiratory syndrome-related coronavirus (MERS-CoV) Coronaviridae

close human contact

Mumps virusParamyxoviridae

droplet contact

MMR vaccine

avoiding close contact with the sick

Parainfluenza virusParamyxoviridae

droplet contact

croup

pneumonia

bronchiolitis

common cold

hand washing

covering mouth when coughing/sneezing

PoliovirusPicornaviridae

fecal-oral

poliomyelitis

Polio vaccine

avoiding contaminated food and water

improved sanitation

Rabies virusRhabdoviridae

animal bite

droplet contact

rabies encephalitis

Post-exposure prophylaxis

rabies vaccine

avoiding rabid animals

Respiratory syncytial virusPneumoviridae

droplet contact

hand to mouth

bronchiolitis

pneumonia

influenza-like syndrome

severe bronchiolitis with pneumonia

ribavirin

hand washing

avoiding close contact with the sick

palivizumab in high risk individuals

covering mouth when coughing/sneezing

Vaccine

Rubella virusTogaviridae

Respiratory and droplet contact

congenital rubella

German measles

MMR vaccine

avoiding close contact with the sick

Severe acute respiratory syndrome coronavirus (SARS-CoV)Coronaviridae

droplet contact

severe acute respiratory syndrome (SARS)

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)Coronaviridae

droplet contact

coronavirus disease 2019 (COVID-19)

hand washing

covering mouth when coughing or sneezing

social distancing

Varicella-zoster virusHerpesviridae

droplet contact

direct contact

chickenpox

herpes zoster

Congenital varicella syndrome

Varicella:

acyclovir

famciclovir

valacyclovir

Zoster:

acyclovir

famciclovir

Varicella:

varicella vaccine

varicella-zoster immunoglobulin

avoiding close contact with the sick

Zoster:

vaccine,varicella-zoster immunoglobulin

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