Human Diseases Caused by Viruses and Prions

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Questions and Answers

What is the mode of transmission of chickenpox virus?

Droplet inhalation (correct)

Vector-borne

Contaminated food and water

Direct contact

What is the name of the virus that causes measles?

RNA virus

Variola virus

DNA virus

rubeola (correct)

What is the name of the vaccine that prevents measles, mumps, and rubella?

Varicella vaccine

MMR vaccine (correct)

Acyclovir vaccine

Vaccinia vaccine

What is the result of initial infection of chickenpox virus?

Chickenpox Signup and view all the answers

What is the name of the disease that occurs in the first trimester of pregnancy due to rubella virus?

Congenital rubella syndrome Signup and view all the answers

Why was smallpox eradication possible?

All of the above Signup and view all the answers

What is the name of the virus that causes smallpox?

Variola virus Signup and view all the answers

What is the name of the vaccine that prevents smallpox?

Vaccinia vaccine Signup and view all the answers

What is the fatality rate of variola major?

33% or more Signup and view all the answers

What is the year when the last case of smallpox from a natural infection occurred?

1977 Signup and view all the answers

Which type of mosquitoes transmit West Nile Fever to humans?

Culex spp. Signup and view all the answers

What is the primary mode of transmission for Genital Herpes?

Direct contact with infected individuals Signup and view all the answers

What is the estimated number of babies born with congenital herpes in the U.S. per year?

1,500-2,200 Signup and view all the answers

What is the type of nucleic acid found in the Herpes Simplex virus?

dsDNA Signup and view all the answers

What is the main way to prevent West Nile Fever?

Mosquito control measures Signup and view all the answers

What is a concern about the use of smallpox vaccine?

Its unknown efficacy in preventing bioterrorism Signup and view all the answers

What is the name of the antiviral drug used to treat Genital Herpes?

Acyclovir Signup and view all the answers

What is the serious complication that can occur in West Nile Fever patients?

Encephalitis Signup and view all the answers

Why should women of childbearing age be vaccinated against measles and German measles?

To prevent fetal death or other birth defects Signup and view all the answers

How many antigen types exist for West Nile Fever?

One Signup and view all the answers

What is characteristic of arboviruses?

They are transmitted by bloodsucking arthropods Signup and view all the answers

What is the usual outcome of encephalitis caused by arboviruses?

High fatality rate Signup and view all the answers

What is the typical outcome of blisters in Genital Herpes patients?

They heal spontaneously Signup and view all the answers

What type of virus causes West Nile Fever?

RNA virus Signup and view all the answers

Which of the following is NOT a mode of transmission for West Nile Fever?

Contaminated food and water Signup and view all the answers

Where was West Nile Fever first identified in the United States?

New York Signup and view all the answers

By what year had West Nile Fever spread to all continental United States?

2006 Signup and view all the answers

What is the primary mode of transmission of arboviruses?

Bloodsucking arthropods Signup and view all the answers

What is the treatment approach for arboviral diseases?

Supportive treatment Signup and view all the answers

What is a characteristic of the vector of arboviruses?

It acquires a lifelong infection Signup and view all the answers

What is a possible complication of HHV-6 infections in immunocompromised individuals?

Pneumonitis Signup and view all the answers

What is the family of viruses that includes human papillomaviruses?

Papillomaviridae Signup and view all the answers

What is the likely route of transmission of viral gastroenteritis?

Fecal-oral route Signup and view all the answers

What is the name of the vaccine available against certain types of HPV?

HPV-16 and 18 vaccine Signup and view all the answers

What is the name of the virus that causes hemorrhagic fever and is a member of the Filoviridae family?

Ebola virus Signup and view all the answers

What is the characteristic of prions that allows them to induce normal proteins to abnormally fold?

Their abnormally folded structure Signup and view all the answers

What is the primary symptom of prion diseases?

Dementia Signup and view all the answers

What is the likely source of the BSE agent that causes vCJD?

Infected cattle Signup and view all the answers

What is the name of the disease caused by HHV-6 infections in infants?

Exanthem subitum Signup and view all the answers

What is the treatment for warts caused by human papillomaviruses?

All of the above Signup and view all the answers

Study Notes

Airborne Diseases

Airborne viruses are propelled from the respiratory tract by coughing, sneezing, or vocalizing
Examples of airborne diseases include Chickenpox (Varicella) and Shingles (Herpes Zoster), Measles (Rubeola), Rubella (German Measles), and Smallpox (Variola)

Chickenpox and Shingles

Caused by a DNA virus, a member of Herpesviridae
Humans serve as the reservoir and source
Acquired by droplet inhalation into the respiratory system
Chickenpox results from initial infection, and vaccine prevents or shortens illness
Shingles (herpes zoster; postherpetic neuralgia) is a reactivated form of chickenpox virus that resides in cranial and sensory neurons
Treatment is supportive, and acyclovir and others are used

Measles

Caused by an RNA virus that enters the body through the respiratory tract
Subacute sclerosing panencephalitis is a rare progressive degeneration of the central nervous system caused by the measles virus
Treatment, prevention, and control involve symptomatic/supportive therapy and attenuated MMR vaccine (measles, mumps, rubella)

Rubella

Caused by an enveloped RNA virus
Mild brief rash is acquired from respiratory droplets
Congenital rubella syndrome is a disastrous disease in the first trimester of pregnancy that can lead to fetal death, premature delivery, or congenital defects
Attenuated vaccine has reduced cases to 1000 and 10 congenital rubella cases per year

Smallpox

Caused by the variola virus, a large, brick-shaped complex virus with linear dsDNA
Transmitted by aerosol or contact, and humans are the only natural host
Clinical forms include Variola major, the most common and severe form, and Variola minor, a less common and less severe form
Eradication was possible due to the disease's obvious clinical features, humans being the only hosts and reservoirs, no asymptomatic carriers, and a short infectivity period (3–4 weeks)

Smallpox Eradication and Vaccination

Last case occurred in Somalia in 1977
Protection is obtained from vaccination using vaccinia virus in a live virus vaccine
Routine immunization is no longer done in the U.S.

West Nile Fever

Transmitted by Culex spp. mosquitoes that feed on sparrows and crows
Human-to-human spread has occurred through blood and organ donation
Only one antigen type exists, and immunity is presumed to be permanent
Clinical manifestations include fever, lymphadenopathy, rash, and serious complications such as encephalitis in >1/100 patients
Treatment, prevention, and control involve serology tests, supportive treatment, and mosquito control measures

Direct Contact Diseases

Transmission occurs through direct personal contact (touching, kissing, sexual contact, contact with body fluids, contact with open wounds)
Many diseases, including AIDS, are transmitted through direct contact

Genital Herpes

Usually caused by herpes simplex type 2, a linear dsDNA enveloped virus
A very common sexually transmitted disease and can be transmitted to infants during vaginal delivery (congenital or neonatal herpes)
Active and latent disease with reactivations occur
Clinical manifestations include fever, burning sensation, genital soreness, and blisters in the infected area
Blisters heal spontaneously, but the virus remains latent and is periodically reactivated
Can be treated with antiviral drugs (e.g., acyclovir)

Congenital Herpes

Congenital (neonatal) herpes is usually HSV-2 and is one of the most life-threatening infections in newborns (~1,500–2,200 babies/year in the U.S.)

Arthropod-Borne Diseases

Arboviruses are transmitted by bloodsucking arthropods from one vertebrate host to another
Multiply in the tissues of the vector without producing disease
Vector acquires a lifelong infection

West Nile Fever (Encephalitis)

Caused by a flavivirus, an RNA virus
Appeared in New York in 1999, causing human and animal deaths
By 2006, it was found in all continental U.S.
Can result in neurologic involvement and blindness
Caesarian section is recommended

Human Herpesvirus 6 Infections

HHV-6 is an enveloped virus with an icosahedral capsid and dsDNA
Tropism is wide, including CD8+, CD4+, natural killer, and epithelial cells
Probably transmitted in saliva
Clinical manifestations include exanthem subitum, a short-lived disease of infants with high fever for 3 to 4 days, followed by a macular rash
Pneumonitis in immunocompromised individuals and implicated in chronic fatigue syndrome, lymphadenitis, and multiple sclerosis in immunocompetent adults
No treatment or prevention measures are available

Warts

Verrucae are horny projections on the skin associated with human papillomaviruses, a DNA virus
More than 100 different strains, infect epithelium and mucus membranes, and cause benign epithelial tumors and cancers
Four major types include plantar warts, verrucae vulgaris, flat or plane warts, and anogenital condylomata (genital warts)
Direct contact and autoinoculation occur
Treatment involves physical destruction, topical application of drug podophyllum, or injection of IFN-α

Genital Warts (Anogenital Condylomata)

A very common sexually transmitted HPV with a 1–6 month incubation period
Warts, usually multiple, are found on external genitalia, in the vagina, or in the rectum
Most infections clear spontaneously
Specific types of HPV cause at least 90% of cervical cancers
Vaccine is available against HPV 16 and 18 (responsible for causing ~80% of cervical cancers)

Gastroenteritis (Viral)

Acute viral gastroenteritis is an inflammation of the stomach or intestines and is an important disease in infants and children
Leading cause of childhood death in developing countries
Probably spread by the fecal-oral route
Caused by four major groups of viruses
Rotavirus, adenovirus, and astrovirus cause ~5–10 million deaths/year worldwide
Viral diarrhea is transmitted by the fecal-oral route
Rotavirus live oral vaccines are used
Norovirus causes ~23 million cases of acute gastroenteritis per year
Usually self-limited disease, and symptomatic/supportive therapy is used

Zoonotic Diseases

Human viral infections in animal reservoirs before transmission to and between humans
RNA viruses, many are on the Select Agents list as potential bioweapons
Examples include Ebola and Marburg viruses, hantaviruses, Lassa fever virus, and Nipah virus

Ebola and Marburg Hemorrhagic Fevers

Viral hemorrhagic fever (VHF) is a severe multisystem syndrome caused by many distinct viruses
Overall host vascular system is damaged, leading to vascular leaking (hemorrhage) and dysfunction (coagulopathy)
Ebola hemorrhagic fever is a member of the single-stranded, negative sense RNA family called the Filoviridae
Infection is severe and ~80% fatal
No known carrier state; fruit bat may be reservoir
Transmission occurs from direct contact with Ebola victim, body fluids, or clinical samples
Internal hemorrhaging occurs
Supportive therapy is used, and no treatment is available
Experimental vaccines are being evaluated

Prion Diseases

Transmissible spongiform encephalopathies are fatal neurogenerative disorders caused by prions
Remains clinically silent for months or years, ending in profound disability or death
Diseases include Kuru, Creutzfeldt-Jacob (CJD) disease, and variant CJD, bovine spongiform encephalopathy (BSE)
Transmission occurs through medical procedures, genetic, or food-borne routes
Prions (protein infectious particles) consist of abnormally folded proteins (PrPsc) that can induce normal forms of protein PrPc to abnormally fold
BSE agent survives gastrointestinal tract passage and is neurotropic, both serving as a source of agent
Dementia is the primary symptom
Usually accompanied by motor dysfunction
Symptoms appear after prolonged incubation and last from months to years prior to death
Produce characteristic spongiform degeneration of brain and deposition of amyloid plaques
Share many characteristics with Alzheimer's disease

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Test your knowledge on various airborne diseases caused by viruses and prions, including chickenpox and shingles, their transmission, and effects on the human body.