Microbiology 5A

Virion

Complete, intact, infectious virus particle

Virus minimum components

Nucleic acid and capsid

Nucleocapsid

Capsid plus nucleic acid

Viral envelope

Additional covering obtained from the host cell membrane during release

Polymerase

Viral enzyme that synthesizes DNA and RNA

Replicase

Viral enzyme that copies RNA

Reverse transcriptase

Viral enzyme that synthesizes DNA from RNA

Viral envelope source

Host cell membrane

Adsorption

Attachment of a virus to a host cell

Penetration

Entry of the virus into the host cell

Uncoating

Removal of the viral capsid to release nucleic acid

Synthesis

Viral genome and proteins are produced inside the host cell

Assembly

Viral components are put together to form new virions

Release

New viruses leave the host cell

Cytopathic effect (CPE)

Virus-induced damage that alters the microscopic appearance of a host cell

Oncogenicity

Ability of a virus to cause cancer

Teratogenic

Ability of a virus to cause birth defects

Latent viral infection

Dormant viral state inside host cells with no symptoms until reactivation

Smallpox (Variola)

Enveloped DNA virus that causes pocks

Smallpox eradication

Worldwide vaccination campaign by the WHO

Eradicated disease

Disease completely eliminated

HSV-1

Herpes simplex virus that causes fever blisters and oral infections

HSV-2

Herpes simplex virus that causes genital herpes

VZV

Varicella-zoster virus that causes chickenpox and shingles

CMV

Cytomegalovirus that infects salivary glands and other organs

EBV

Epstein-Barr virus that causes mononucleosis

HHV-6 and HHV-7

Cause roseola

KSHV (HHV-8)

Associated with Kaposi sarcoma

Most severe herpesvirus infections

AIDS patients

HSV-1 lesions

Oropharynx, face, and mouth

HSV-2 lesions

Genitalia, thighs, and buttocks

HSV-2 symptoms

Malaise, anorexia, fever, swollen groin, painful vesicles, urethritis, painful urination, cervicitis, and itching

Neonatal herpes

Acquired during birth from an infected mother, most commonly HSV-2

Chickenpox

Primary infection caused by Varicella-zoster virus

Shingles

Reactivation of latent Varicella-zoster virus

Varicella transmission

Respiratory droplets and fluid from active lesions

Varicella incubation period

10–20 days

Varicella contagious period

One to two days before rash develops

Varicella symptoms

Fever and abundant rash with lesions that crust and heal

VZV latency site

Sensory neurons in ganglia

Shingles reactivation triggers

Stress, immunosuppression, surgery, X-rays, or malignancy

CMV transmission

Saliva, respiratory mucus, milk, urine, semen, and cervical secretions

High-risk groups for severe CMV

Fetuses, newborns, and immunodeficient adults

EBV disease

Infectious mononucleosis

Burkitt lymphoma

B-cell cancer associated with Epstein-Barr virus in African children

HBV

DNA hepatitis virus

HAV

RNA hepatitis virus

HCV

RNA hepatitis virus

Hepatitis viruses

Cause inflammation of the liver

Jaundice

Yellow skin caused by bilirubin accumulation

Hepatitis vaccines

Available for Hepatitis A and Hepatitis B

Hepatitis A

Fecal-oral virus with mild jaundice and short duration

HBV high-risk groups

Multiple sexual partners, injection drug users, and occupations exposed to blood

Chronic HBV complication

Hepatocellular carcinoma

HBIG

Hepatitis B immune globulin that provides passive artificial immunity

Hepatitis C

Silent epidemic because symptoms often take years to appear

HCV transmission

Blood contact, needle sharing, blood transfusions, occasionally body fluids and placenta

HPV

Sexually transmitted virus that causes genital warts

HPV-16

High-risk strain associated with cervical and penile cancer

HPV-18

High-risk strain associated with cervical and penile cancer

HPV wart treatment

Cauterization, freezing, or laser surgery

HPV transmission

Direct contact with warts, contaminated fomites, and autoinoculation

Influenza A

Primary cause of seasonal influenza outbreaks

Influenza B

Causes influenza but less commonly than Influenza A

Influenza C

Causes mild respiratory illness

Hemagglutinin (H)

Viral protein that binds respiratory receptors and allows viral entry

Neuraminidase (N)

Viral enzyme that breaks down respiratory mucus and helps viruses exit host cells

Antigenic shift

Major genetic change caused by exchange of genes between influenza viruses from different species

Antigenic drift

Small continual mutations in influenza glycoproteins

Influenza reservoir

Wild aquatic birds such as ducks and geese

Influenza transmission

Respiratory droplets and contaminated fomites

Influenza symptoms

Fever, headache, muscle aches, sore throat, shortness of breath, and cough

Annual influenza vaccine

Reformulated each year because of antigenic drift

Measles (Rubeola)

Causes a diffuse rash called an exanthem

Koplik spots

White lesions inside the mouth associated with measles

SSPE

Subacute sclerosing panencephalitis, a rare neurological complication of measles

Mumps

Causes epidemic parotitis

Mumps symptoms

Fever, nasal discharge, muscle pain, malaise, and swollen salivary glands

Mumps target organs

Testes, ovaries, thyroid gland, meninges, pancreas, heart, and kidneys

Rubella

German measles and the R in STORCH

Rubella significance

Can cross the placenta and cause congenital infections or birth defects

Rubella symptoms

Mild fever, sore throat, lymphadenopathy, rash that usually resolves in 3 days

RSV

Respiratory syncytial virus that infects the respiratory tract

RSV high-risk group

Infants 6 months of age or younger

RSV symptoms

Fever, rhinitis, pharyngitis, otitis, and giant multinucleated cells in the respiratory tract

Synagis

Monoclonal antibody that blocks RSV attachment to cells

Ribavirin

Antiviral aerosol used to treat RSV

RSV vaccine

No effective vaccine currently available

Rabies transmission

Animal bites, scratches, and inhalation of infected droplets

Zoonotic disease

Disease transmitted from animals to humans

Rabies reservoirs

Wild canines, skunks, raccoons, cats, and bats

Furious rabies

Agitation, disorientation, seizures, twitching, painful swallowing, and hydrophobia

Dumb rabies

Paralysis, disorientation, and stupor

Rabies post-exposure treatment

Active immunization with vaccine plus passive immunization with antibodies

HIV

Retrovirus that converts RNA into DNA using reverse transcriptase

HIV transmission

Sexual intercourse and blood or blood products

HIV positive

Does not necessarily mean the person has AIDS

AIDS diagnosis

CD4 count below 200 cells per microliter of blood

Kaposi sarcoma, non-Hodgkin lymphoma, and cervical cancer

Cancer commonly seen in AIDS patients

HAART

Highly active antiretroviral therapy using multiple antiviral drugs