VIRUSES
Viruses are small obligate intracellular parasites, which by definition contain either a RNA or DNA genome surrounded by a protective, virus-coded protein coat. Viruses may be viewed as mobile genetic elements, most probably of cellular origin and characterized by a long co-evolution of virus and host. For propagation viruses depend on specialized host cells supplying the complex metabolic and biosynthetic machinery of eukaryotic or prokaryotic cells. A complete virus particle is called a virion. The main function of the virion is to deliver its DNA or RNA genome into the host cell so that the genome can be expressed (transcribed and translated) by the host cell. The viral genome, often with associated basic proteins, is packaged inside a symmetric protein capsid. The nucleic acid-associated protein, called nucleoprotein, together with the genome, forms the nucleocapsid. In enveloped viruses, the nucleocapsid is surrounded by a lipid bilayer derived from the modified host cell membrane and studded with an outer layer of virus envelope glycoproteins.
Kinds of Viruses
- Common Name: Variola Virus
- Scientific Name: Variola vera
Classification - DNA
- Double-stranded
- Enveloped
- Brick-shaped
Significance/Medical Importance - Smallpox is an acute, contagious disease with two main forms, variola major and variola minor, both of which cause similar lesions
- Transmission occurs via respiratory droplets (primary route of transmission), or via fine-particle aerosol, or skin inoculation. The conjunctiva or placenta may be occasional portals of entry
- The acyclic nucleoside phosphonate analogue cidofovir has been shown to have activity against variola virus in cell culture.
Common Name: Human Herpes Virus/Genital Herpes
Scientific Name: Herpes SimplexVirus
Classification
Scientific Name: Herpes SimplexVirus
Classification
- DNA
- Double-stranded
- Enveloped
- Icosahedral capsid
Significance/Medical Importance - Genital Herpes is a viral STI that is spread through skin to skin contact with an infected person.
- Herpes Simplex 1 is the common cold sore that is often found around your mouth but it can be spread to the genitals through oral sex. Herpes Simplex 2 is more commonly found on the genitals but it can be spread to the mouth through oral sex. The virus can also be passed from mother to baby during childbirth, especially if you have an outbreak during the time of delivery.
- Medications can help reduce the incidence of herpes sores, but herpes cannot be cured. Outbreaks tend to be farther apart over time and cover a smaller area of skin.
Common Name: Varicella Zoster Virus
Scientific Name: Varicella Zoster
Classification
Scientific Name: Varicella Zoster
Classification
- DNA
- Double-stranded
- Enveloped
- Icosahedral capsid
Significance/Medical Importance - Chickenpox: Varicella/chickenpox is a primary infection with VZV. It occurs mainly in children and is characterized by generalized itchy, vesicular eruptions/rash and fever.
- Shingles: Shingles/Zoster is due to reactivation of latent VZV. It is characterized by a painful eruption of vesicular lesions along with inflammation in the skin area supplied by the associated dorsal root or cranial nerve sensory ganglia.
- Treatment: Acyclovir (ACV), Oral famciclovir, intravenous foscarnet.
Scientific Name: Human papillomavirus
Classification
Classification
- DNA
- Double-stranded
- Non-Enveloped
- Closed-circular
Significance/Medical Importance - HPV viruses infect the basal epithelial cells of cutaneous and mucosal keratinized epithelia. Cutaneous infections affect most commonly the hands and feet, while mucosal infections target the lining of the mouth (small nodules can develop into cancerous cells), throat, respiratory tract, and anogenital epithelium. When mucosal infections do not clear spontaneously on their own, they can progress into cervical intraepithelial neoplasm, which can lead to cervical cancer.
- It is one of the most common sexually transmitted diseases in North America.
- Treatment: Liquid nitrogen, Gardasil and Cervarix
Scientific Name: Human papillomavirus
Classification
Classification
- DNA
- Double-stranded
- Partially Double-stranded and Partly single-stranded
- Envelope circular
Significance/Medical Importance - Acute hepatitis B infection: Persons with acute hepatitis B infection may be asymptomatic or present with a clinical picture varying from mild to severe hepatitis.
- Chronic hepatitis B infection: Defined as the persistence of HBsAg for more than 6 months. They are at substantially increased risk for developing chronic liver diseases, including cirrhosis of the liver and primary hepatocellular carcinoma.
- Treatment:interferon-α, pegylated interferon α-2a, lamivudine, adefovir, entecavir, telbivudine, and tenofovir
Common Name: B19 virus, Parvovirus B19
Scientific Name: Primate erythropar-vovirus 1
Classification
Scientific Name: Primate erythropar-vovirus 1
Classification
- DNA
- Single-stranded
- Enveloped
- Icosahedral capsid
Significance/Medical Importance - Complications t thought to be associated with parvovirus B19 infection include encephalopathy, epilepsy, meningitis, myocarditis, dilated cardiomyopathy, and autoimmune hepatitis.
- Erythema infectiosum (Fifth Disease) is the most recognizable presentation of parvovirus B19 infection.
- In young adults, infection can be associated with papular, purpuric, "gloves and socks"syndrome, which presents as symmetric, painful erythaema and oedema of the feet and hands.
- Transmission occurs most commonly by personal contact.
Scientific Name: Poliovirus
Classification
Classification
- RNA
- Single-stranded
- Non-Enveloped
- Icosahedral capsid
Significance/Medical Importance - Poliomyelitis (polio) is an infection caused by a virus called poliovirus that enters the body through the mouth mainly through food or water that is contaminated with feces as a result of poor personal hygiene, poor sanitation or poor control of sewage.
- Treatment: Inactivated polio virus vaccines (IPV) which contains only dead virus and is given by injection; and oral poliovirus vaccine (OPV) which contains live weakened virus which is administered by drops into the mouth.
Scientific Name: Human Rhinovirus
Classification
Classification
- RNA
- Single-stranded
- Non-Enveloped
- Icosahedral
Significance/Medical Importance - Human rhinovirus (HVR) infections are the cause of about 50% of all common colds and asthma, and chronic obstructive pulmonary diseases (COPD) exacerbations.
- Airborne transmission of aerosols and droplets is the major route of dissemination of the virus, which can enter the body through the respiratory tract by the nose and mouth.
- Treatment: zinc gluconate lozenges, human interferon α2, Antivirals.
Scientific Name: Rubella Virus
Classification
Classification
- RNA
- Single-stranded
- Non-Enveloped
- Spherical
Significance/Medical Importance - Rubella: Mild infection characterized by rash starting on the face and gradually spreading to the feet, fever, lymphadenopathy, and other flu-like symptoms such as coughing, sore throat, and sneezing.
- Congenital rubella syndrome: Women in their first trimester who contract rubella have an increased risk of passing the infection to the developing fetus.
- The virus is transmitted by aerosols from the respiratory tract in infected individuals.
Scientific Name: Influenza Vitus Type A
Classification
Classification
- RNA
- Single-stranded
- Enveloped
- Roughly Spherical
Significance/Medical Importance - An acute viral disease of the upper respiratory tract characterized by fever (temperature 37.8ºC or above), headache, myalgia, malaise, sore throat, non-productive cough, sneezing and nasal discharge.
- A pandemic that occurred in 1957-1958 (Asian flu) was caused by influenza virus A subtype H2N2.
- Another influenza pandemic that occurred in 1968-1969 (Hong Kong flu), was caused by an H3N2 strain of influenza.
- Highly communicable.
- Treatment: Fluids and rest, Antiviral agents, Antibiotic treatment
Scientific Name: Mumps Virus
Classification
Classification
- RNA
- Single-stranded
- Enveloped
- Roughly Spherical with large spikes
Significance/Medical Importance - It is a causative agent of mumps, a well-known common childhood disease characterized by swelling of the parotid glands, salivary glands and other epithelial tissues, causing high morbidity and in some cases more serious complications such as deafness.
- It is considered a vaccine-preventable disease.
Scientific Name: Human Coronavirus
Classification
Classification
- RNA
- Single-stranded
- Enveloped
- Spherical
Significance/Medical Importance - HCoV-229E and HCoV-OC43 cause the common cold, a self-limiting upper respiratory tract infection. Infection can lead to a number of illnesses such as bronchitis, gastroenteritis, progressive demyelinating encephalitis, diarrhea, peritonitis, nasal obstruction, rhinorrhea, sneezing, sore throat and cough.
- Infection can be transmitted through inhalation of respiratory droplet aerosols; virus can also be spread via the fecal-oral route, and through fomites.
Scientific Name: Rabies virus
Classification
Classification
- RNA
- Single-stranded
- Enveloped
- bullet-shaped
Significance/Medical Importance - Furious rabies : dominated by encephalitis, and presents with hydrophobia, delirium, and agitation. Hydrophobia is the symptom most identified with rabies; patients have severe difficulty in swallowing and can become fearful at the sight of water despite an intense thirst.
- Paralytic (dumb) rabies: lack signs of cortical irritation, instead presenting with ascending paralysis or symmetrical tetraparalysis.
- Rabies is most commonly transmitted to humans via the bite of a rabies-infected animal.
Credits to the owner: http://www.ncbi.nlm.nih.gov/books/NBK8174/