Virology: Chapter 1 - The Virus

A type of virus transmission where a virus enters a plant from the external environment, often through insect vectors or contaminated tools.

A type of virus transmission where a virus is passed from a parent plant to its offspring through seeds or asexual propagation.

A type of plant pathogen that consists solely of a small, circular single-stranded RNA molecule without a protein coat. It replicates using host enzymes and does not produce proteins.

A type of infectious agent that consists of a misfolded protein that can cause neurodegenerative diseases in humans and mammals. It replicates by converting normal proteins into misfolded versions.

A family of DNA viruses that have icosahedral capsids and contain supercoiled, double-stranded, circular DNA.

A subfamily of Papovaviridae that infect epithelial cells and cause warts and other hyperplastic lesions.

A group of viruses that infect epithelial cells and cause tumor formation, including both benign and malignant tumors.

Small, non-enveloped DNA viruses that have icosahedral capsids and contain supercoiled, double-stranded, circular DNA.

HSV-1 and HSV-2 are spread through direct contact with virus-containing secretions like saliva, skin lesions, or respiratory secretions.

HSV-1 is commonly found in lesions above the waist, while HSV-2 is more common below the waist.

HSV-1 and HSV-2 multiply in epithelial cells of the mucosal surface, leading to the formation of vesicles containing infectious virus.

In healthy individuals, the immune system's cytotoxic T lymphocytes recognize and destroy infected cells before progeny virus is produced.

HSV-1 and HSV-2 can establish a lifelong latent infection in regional ganglia, allowing the virus to reactivate later.

Primary infections of the upper body can be asymptomatic but can also manifest as gingivostomatitis in children, pharyngitis/tonsillitis in adults, and keratoconjunctivitis, which can lead to blindness.

HSV-1 infections of the central nervous system can lead to encephalitis, a serious condition with high mortality and neurological deficits.

Primary genital herpes infections can be asymptomatic but can manifest as painful vesiculo-ulcerative lesions on the vulva, cervix, vagina in women and the penis in men.

Hepatitis B virus infection is present in all body fluids of an infected individual.

The time between exposure to the virus and the appearance of symptoms.

An individual with a chronic infection, meaning they have the virus for a long time.

The number of virus particles present in a sample. A high titer means there are many virus particles.

Inflammation of the liver, usually caused by a viral infection.

A phase of hepatitis B infection characterized by yellowing of the skin and eyes.

A phase of hepatitis B infection characterized by mild symptoms like fever and fatigue.

The ability of the body's immune system to fight off infection, particularly through cell-mediated immune response.

Rubella virus is a member of the Togaviridae family, specifically the alphavirus genus. Like alphaviruses, it has an enveloped structure with a single-stranded RNA genome.

Rubella virus is primarily spread through respiratory secretions, like saliva or droplets from an infected individual's cough or sneeze.

Rubella infection generally causes mild symptoms, including a characteristic rash that looks like small red spots spread across the body, and swollen lymph nodes at the back of the head.

Rubella infection during pregnancy can lead to serious developmental problems for the developing fetus, potentially causing damage to the heart, eyes, liver, and brain.

Rubella virus's incubation period is typically 9 to 11 days, meaning that's the time between exposure to the virus and the onset of symptoms.

Congenital rubella syndrome occurs when a pregnant woman is infected with rubella, resulting in birth defects in the baby. These defects can include heart problems, cataracts, hearing loss, and brain damage.

A live attenuated rubella vaccine is included in routine childhood vaccinations to prevent rubella infection. It is not typically given to pregnant women or individuals with weakened immune systems.

Flaviviridae is a family of enveloped viruses with a single-stranded RNA genome. Members of this family are known for having three structural proteins.

Hepatitis C Virus (HCV) is the main cause of post-transfusion hepatitis, affecting individuals who receive blood transfusions. It's also prevalent among intravenous drug users, those undergoing hemodialysis, and people who get tattoos.

HCV can be transmitted through sexual contact, meaning infected individuals can spread the virus to their partners during sexual activity. Mothers infected with HCV can also pass the virus to their newborns during birth.

Once HCV enters the body, it replicates within the liver cells, known as hepatocytes, and also multiplies inside immune cells like lymphocytes and macrophages.

HCV damages liver cells through two mechanisms: direct attack by the virus's genetic material and the body's own immune response. Cytotoxic T cells, a type of immune cell, play a role in this immune response and can further harm the liver.

HCV is an RNA virus, which typically doesn't cause chronic infections or cancer like DNA viruses do. However, certain HCV strains have been linked to hepatocellular carcinoma, a type of liver cancer, even in the absence of liver scarring (cirrhosis). Treatment with interferon-γ (IFN-γ) has also been associated with treatment failures in certain HCV infections.

Most HCV infections are asymptomatic, meaning individuals don't experience any symptoms. However, roughly 25% of HCV infections cause acute hepatitis, leading to symptoms like jaundice. Importantly, a significant proportion of individuals progress to chronic hepatitis and cirrhosis. Sadly, some of these individuals eventually develop hepatocellular carcinoma.

HCV can impact not only the liver but also other tissues, particularly the skin. Common skin conditions associated with HCV include mixed cryoglobulinemia, porphyria cutanea tarda, lichen planus, and necrolytic acral erythema.

Skin manifestations can sometimes be the initial sign of HCV infection. If you notice any unusual skin problems, it's crucial to get tested for HCV. Most importantly, skin issues usually improve after successful HCV treatment or when the virus is cleared from the body.

The period after acute HIV infection, characterized by a clinically asymptomatic state where HIV replication is controlled by the immune system, but the virus persists in a latent state within a small number of infected cells. This phase can last for several years and is marked by a decline in CD4+ cell count over time.

Immune cells primarily affected by HIV infection, responsible for coordinating immune responses and defending against infections. Their depletion leads to immune system impairment and vulnerability to opportunistic infections.

A specific type of immune response involving specialized cells that directly destroy infected cells, playing a crucial role in controlling HIV replication during the latent period.

The gradual but continuous decline in the number of CD4+ cells, a defining feature of HIV progression, ultimately leading to impaired immune function and susceptibility to opportunistic infections.

A key marker of HIV progression to AIDS, signifying a severely compromised immune system with a high risk of developing opportunistic infections. Once the CD4+ count falls below this level, the patient is diagnosed with AIDS.

Infections that take advantage of a weakened immune system, often characteristic of AIDS progression, and frequently contribute to the decline in health and survival of individuals with advanced HIV.

The final stage of HIV infection, characterized by severe immune suppression and the development of life-threatening opportunistic infections. This phase is a direct consequence of the progressive decline in the number of CD4+ cells.

A diverse group of diseases, including cancers, that occur more frequently and aggressively in people with AIDS due to the weakened immune system.