Families of viruses

Hepadnaviridae...Herpesviridae...Orthomyxoviridae...Picornaviridae...Flaviviridae

Hepadnaviridae


All of the known hepadnaviruses are hepatotropic, eg. Hepatitis B virus (HBV). infecting liver cells, and all can cause hepatitis in known host. Hepatitis inflammation of the liver. It can be caused by hepatitis viruses, other viruses and non-infectious agents such as alcohol.

Diseases Caused

1) Genus Orthohepadnavirus

Disease Natural Host
Hepatitis B (HBV) Humans, Chimps, Gibbons, Monkeys
Hepatitis B Ground Squirrels, Woodchucks, Chipmunks
Hepatitis B Woodchucks

2) Genus Avihepadnavirus

Disease Natural Host

Duck Hepatitis B Ducks, Geese

Genome

- partial ds DNA, circular, monopartite, smallest at 3.2kb in length

- two uneven strands of DNA. One has a negative-sense orientation, and the other, shorter, strand has a positive-sense orientation
- it is a group 7 virus, replication involves and RNA intermediate

Morphology

- roughly spherical, icosahedral nucleocapsid.

- Replication: Violates Central Dogma-DNA->RNA->DNA which they transcribe back into cDNA using reverse transcriptase

Clinical Symptoms

- Jaundice, fatigue, abdominal pain, nausea
*Note: This are acute symptoms.

Transmission

- Blood-borne, sexual

Prevention

- Recombinant HBV surface antigen vaccine or HBV immunoglobulin post-exposure prophylaxis

- Avoid sexual contact/ bloog contact
- Vaccines against hepatitis B were introduced in the early 80s and babies were all vaccinated.

Symptoms of Acute Infection

Symptoms usually activate 6 weeks to 6 months afterwards acknowledgment to the virus. In adults, aboriginal affection can cover abhorrence, loss of appetite, vomiting, fatigue, and belly cramps and jaundice. Persons can accept all or alone a few of the aloft signs and symptoms. 50% of adults with a new infection accept no affection. Over 90% of infants, 50% of children, and 5% of adults with astute hepatitis B will advance abiding or abiding infection. Abiding hepatitis B may advance to alarmist ache including cirrhosis and alarmist cancer.

Symptoms of Chronic Infection

Most patients do not undergo any symptoms. Abiding hepatitis B may advance to alarmist ache including cirrhosis and liver cancer.

Herpesviridae

A heterogeneous family of morphologically similar viruses, all of which contain double-stranded DNA and infect humans and a wide variety of other vertebrates as well as some invertebrates, such as oysters.Human herpesvirus infections are endemic and sexual contact is a significant method of transmission for several including both herpes simplex virus 1 and 2 (HSV-1, HSV-2), also human cytomegalovirus (HHV-5) and likely Karposi's sarcoma herpesvirus (HHV-8).

picture extracted from: http://upload.wikimedia.org/wikipedia/commons/4/4d/Herpesviridae_EM_PHIL_2171_lores.jpg

Virions are enveloped, ether sensitive, and vary up to 200 nm in diameter; the nucleocapsids are 100 nm in diameter and of icosahedral symmetry, with 162 capsomeres.The family is subdivided into three subfamilies Alphaherpesvirinae, Betaherpesvirinae, and Gammaherpesvirinae.

Symptoms of Herpes Simplex

An infection by a herpes simplex virusis marked by watery blisters in the skin or mucous membranes of the mouth, lips or genitals.

Symptoms of Varicella Zoster
An infection of Varicella zoster virus will cause fever, lesions. Lesions heal with a scab.


picture extracted from : http://health.allrefer.com/health/chicken-pox-treatment-chicken-pox.html

Orthomyxoviridae

Influenza virus is transmitted from person to person in droplets released by sneezing and coughing. Some of the inhaled virus lands in the lower respiratory tract. The cough may be persistent but the most prominent symptoms of influenza are systemic: fever, muscle aches.

Vaccines: Isolated HA gives good serological protection. Vaccines are produced by reassortment of egg-adapted strains with the required HA type. Large amounts of virus are then grown in embryonated eggs, being purified and formalin inactivated. The amount of doses given to a patient depends on the age of patient.

Orthomyxoviridae

For Orthomyxoviridae, there are 2 Influenza virus types A and B. They causes of acute respiratory illnesses. Both virus types cause epidemics of considerable morbidity and mortality.

Influenza virus A causes of all flu pandemics and infect humans, other mammals and birds
Influenza virus B infect humans and seals
Influenza virus C infects humans and pigs.

Picornaviridae

It is the oldest viruses which found in ancient Egypt at 1400 B.C. Picornaviruses are also among the most diverse viruses, with over 200 serotypes causing infections such as Polio, Hepatitis A, and the common cold. Foot-and-Mouth Disease Virus (genus: Apthovirus), which causes infections in livestock, was one of the first viruses to be recognized; it was discovered by Loeffler and Frosch in 1898.
Picornaviruses contain positive sense, single-stranded RNA that is approximately 7-8 kilobases long.
The viral RNA is infectious and replication takes place in the cytoplasm.
The virus has an IRES (Internal Ribosomal Entry Site) which distinguishes it from many other RNA viruses.
The virus is naked with an icosahedral capsid.
The capsid is one of the smallest of all viruses with a diameter of only 27-30nm.
Translation and cleavage of viral polypeptides produces eleven distinct proteins.

Flaviviridae

Symptoms of Dengue Fever & Dengue Hemorrhagic FeverDengue fever usually starts suddenly with:
- high fever
- severe headache
- vomiting
- pain behind the eyes
- muscle and joint pain

A rash appears 3 to 4 days after the start of the fever. The illness can last up to 10 days, but complete recovery can take as long as a month. Most dengue infections result in relatively mild illness, but some can progress to dengue hemorrhagic fever.

With dengue hemorrhagic fever, the blood vessels start to leak and cause:
- bleeding from the nose, mouth, and gums
- Bruising (a sign of bleeding inside the body)

In severity, the blood vessels can collapse, causing shock. Dengue hemorrhagic fever is fatal in about 5 percent of cases.