1. Introduction to Viruses that Infect Humans: The DNA Viruses

2. Host Range
A cell has to have a specific structure or receptor on its surface for a virus to be able to attach to it.
A cell has to contain all of the enzymes and materials needed to
It can be for one species or for many different ones.
Most are specific and infect just humans, dogs, and plants.

3. Animal Virus Replication
1. Absorption 2. Penetraion/ uncoating of genome 3. Duplication/synthesis 4. Assembly 5. Release

4. Ways Cells Are Damaged By Viruses
changes in size and shape
cytoplasmic inclusion bodies
nuclear inclusion bodies
cells fuse to form multi-nucleated cells
cell lysis
alter DNA
transform cells into cancerous cells

5. Virus lagnape
Are obligate parasites that infect animals, plants, and other microbes. Viruses are limited to a particular host or cell type.
Most DNA viruses bud off of the nucleus and most RNA viruses multiply and are released from the cytoplasm.
Viral infections can range from very mild similar to a cold, to life threatening like HIV.
Several viruses are able to cross the placenta and cause developmental disturbances.
The term teratogenic is used for the cross infection from mother to the embryo or fetus.
A virus can become a permanent resident of the host cell and just stay latent at times.
Some cell changes from virus infections are visible to the naked eye ex: inclusion bodies seen from Rabies victims.
The first known virus, tobacco mosaic virus, was discovered by Martinus Beijerinck in 1898, and now more than 5,000 types of virus have been described.
The study of viruses is known as virology, and is a branch of microbiology

7. POXVIRUSES general info
produce eruptive skin pustules called pocks or pox that leave scars
largest and most complex animal viruses
have the largest genome of all viruses and multiply in the cytoplasm in well defined sites called factory areas which appear as inclusion bodies infected cells.
multiply in cytoplasm in factory areas
they are an enveloped DNA virus
Variola - cause of smallpox
Vaccinia - (agent of cowpox) closely related virus used in vaccines
Monkeypox
Cowpox
Molluscipox

8. Smallpox (Variola)

9. first disease to be eliminated by a live vaccination (due to Edward Jenner) -exposure through inhalation (respiratory route) or skin (scabs) contact
-infection associated with fever, malaise, prostration and rash
-Variola major - highly virulent-caused toxemia, shock and intravascular coagulation(20-40% mortality)
-Variola minor - less virulent (1% mortality) milder symptoms and a lower death rate.
-killed majority of some tribes of Native Americans, and people of Hawaii. -routine vaccination ended in US in 1972
-the last naturally occuring case of smallpox occured in 1977
-vaccine was reintroduced in 2002 because of possible bioterrorism. Mainly inlisted officers/military receive the vaccine when traveling overseas
-Infection includes fever, malaise, prostration. Later a rash begins in the pharynx, spreads to the face, and progresses to the extremities.
-Smallpox caused million deaths during the 1900's. As recently as 1967, 2 million people died from smallpox. WHO declared smallpox to be eradicated in 1979.
The CDC and its equivalent in Russia each kept samples of the virus. Threat of bioterrorism has brought the vaccine back.

10. Cowpox
Cowpox virus, from the genus Orthpoxvirus, is another poxvirus that causes human disease through zoonosis.

11. Epidemiology
Cowpox virus has been found only in Europe and in adjacent parts of the former Soviet Union.
the reservoir hosts of cowpox virus are rodents, from which it can occasionally spread to cats, cows, humans, and zoo animals, including large cats and elephants.
Transmission to humans has traditionally occurred via contact with the infected teats of milking cows.
infection is seen more commonly among domestic cats, from which it can be transmitted to humans.

12. Incubation, Symptomatology, and Outcome
Incubation period is generally 9 to 10 days.
Infection with cowpox virus in humans produces localized, pustular lesions at the site of their introduction into the skin.
The lesion is similar to that caused by vaccination, although the inflammatory response is greater.
The lesions in humans usually appear on the hands: on the thumbs, the first interdigital cleft, and the forefinger.
Fever and myalgia may be present in some cases, but this is rare.
Secondary lesions occur only in individuals with immunological deficiencies.

13. Human infections with monkeypox virus, from the genus Orthopoxvirus, were first observed in West and Central Africa during the early 1970s, after smallpox had already been eradicated in this region. It also appeared in the Midwestern United States in Although the signs and symptoms of monkeypox are very similar to those of smallpox, this virus is significantly different
Monkey pox

14. Epidemiology
The epidemiology of monkeypox is completely different from that of smallpox.
This virus is a rare zoonosis found only in the small villages of the tropical rain forests of western and central Africa, with cases mostly reported in Zaire.
As a result of intensive surveillance efforts conducted by the World Health Organization, only 400 cases were reported worldwide from the time infection by monkeypox virus was first observed in 1970 to the time when surveillance ceased in 1986.
Monkeypox virus is believed to be transmitted through direct contact with wild animals killed for food, such as squirrels and monkeys.
A very important feature of monkeypox is that person-to-person transmission is rare, accounting for less than 1/3 of observed cases.

15. Incubation period, Pathogenesis, and Pathology
Incubation period is between days, usually 12 days.
Very similar to smallpox where the virus replicates in lymphoid tissues, however, the viral entry occurs by small lesions and it may also occur via respiratory tract.

16. Prevention and Management
Vaccination with smallpox vaccine immunizes against monkeypox, but it is not justified since the disease is so rare. Vaccinia vaccination is recommended for laboratory workers who directly handle cultures or animals infected with monkeypox virus.
Management for monkeypox involves effective surveillance efforts such as those undertaken by the World Health Organization prior to 1980.
An important thing to remember is that unlike smallpox, human monkeypox has a lower capacity for human spread. This makes identification and containment much more accessible.

17. Molluscipoxvirus

18. Epidemiology
This disease is distributed throughout the world, with highest incidence occuring in the Pacific islands.
In endemic regions, it is primarily an infection of children. It is most common in sexually active young people in the United States.
Infection results from either sexual or skin-to-skin contact with an infected person.
They may be spread to other body sites through scratching and self-inoculation.
AIDS patients suffer from an atypical version of the disease, which attacks the skin of the face and forms tumorlike growths, as shown in the image above.

19. Incubation Period and Symptoms
Incubation period is generally 1-3 months.
The infection is confined to the skin and does not cause serious problems.
The virus causes small, round, firm bumps on the skin.
The bumps tend to develop on the sex organs, abdomen, or thighs.
The bumps may be pink, pearly-white, or the same color as the rest of the skin in the affected area. There may be one bump or many.
They are not painful or tender unless they become infected. Sometimes they itch a little.

20. Herpes

21. Herpes general info
large enveloped icosahedral capsid housing a core of double-stranded DNA
replication within nucleus; viral release usually accompanied by cell lysis
larger family; 8 infect humans (HHV=human Herpes virus)
latency and recurrent infections, mucous membranes are targets for the virus
recurrent infection triggered by fever, UV radiation, stress or mechanical injury
latency complications and recurrent infections more severe with age, chemotherapy, etc.
most common and serious opportunists among AIDS patients
most common sporadic form of viral encephalitis in the U.S.
humans are the only natural reservoir for the virus

22. Comparative Epidemiology and Pathology of Herpes Simplex, Types 1 and 2
HSV-1
HSV-2
Usual Etiologic Agent of
Ocular herpes Gingivostomatitis Pharyngitis
Herpes genitialis
Transmission
Close contact, usually of face
Sexual or intimate contact
Latency
Occurs in trigeminal ganglion
Occurs primarily in sacral ganglia
Skin Lesions
On face, mouth, cold sores, fever blisters (occurs in early childhood)
On internal, external genitalia, thighs, buttocks (occurs in ages 14-29) (can spread without visible lesions)
Complications Whitlows Neonatal encephalitis Treatment
Among healthcare personnel working on oral cavity Causes up to 30% of cases acyclovir, famciclovir, and valacyclovir
Among obstetric, gynecological personnel Causes most cases through contact with birth conal acyclovir, famciclovir, and valacycclovir

23. Varicella-Zoster Virus (Herpesvirus)
This Herpesvirus causes both varicella (commonly known as chickenpox) and a recurrent infection called herpes zoster (known as shingles).

24. Varicella AKA Chickenpox
Respiratory tract is chief portal of entry and site of replication.
communicable through respiratory droplets or active skin lesion fluids
incubation period is days; first symptoms are fever and rash most contagious 1 to 2 days prior to the development of the rash
Skin lesions appear, and progress to scabs, sometimes leaving a scar.
virus enters neurons and remain latent; may later reactivate in the form of shingles

25. Herpes zoster (known as shingles).
As with other herpes viruses, most cases of varicella result in the entry of the varicella into skin sensory nerves, especially thoracic and trigeminal nerves, where the virus goes dormant.
may either remain dormant indefinately or later reemerge in the form of shingles with its character asymmetrical distribution on the skin of the trunk or head or occasionally the neck or limbs.
Some possible causes may be stress or a weakened immune system.
Anyone who has ever had chickenpox is at risk for the development of shingles, although it occurs most commonly in people over the age of 60.

27. Cytomegalovirus Group (CMV) Herpesvirus
Most often seen virus in humans
Most prevalent fetal infection
More common among drug abusers and homosexual population
Transmitted through saliva, respiratory mucus, milk, urine, semen and cervical secretions
Usually through sexual contact, vaginal birth, transplacental infection, blood transfusion or organ transplantation
Newborns infected with CMV often show neurological sequelae, including visual and hearing problems [perinatal CMV, which occurs after exposure to mother's infected birth canal, is usually asymptomatic]
Newborns tend to develop a more virulent for of cytomegalovirus more than any other age group

29. Epstein-Barr Virus
Lymphatic disease, can transform lymphocytes to malignant cells through expression of its genes
Direct oral contact is most common mode of transmission, but transfer through blood transfusions or organ transplantation is possible (can be asymptomatic).
The niche for Epstein-Barr virus in humans are the lymphoid tissues and salivary glands
In less-developed areas of the world, EBV occurs more in younger childhood. In industrialized nations, exposure usually doesn't occur until adolescence
By midlife, 90-95% of population shows serological evidence of infection
Sore throat, high fever and swollen lymph glands in the neck are the most common symptoms. Blood tests show infected B cells and later infected T cells

30. HHV-6 Causes roseola, an acute febrile disease in babies
Characteristics are similar to CMV
Virus enters and replicates in T lymphocytes, macrophages, and salivary gland tissues
Immunosuppressed patients with renal or bone marrow transplants often acquire HHV-6 infections
Known for causing encephalitis and neurological disease, which is known to lead to Multiple Sclerosis (MS) [Over 70% of patients with MS show evidence of being infected with HHV-6]
Link between HHV-6 and several types of cancer (Hodgkin lympoma, oral carcinoma, T-cell leukemias)

31. Hepadnaviruses
Hepatitis A-E Viruses -Enveloped viruses that have never been grown in tissue culture and have a genome containing both double- and single-stranded DNA

32. Hepatitis Hepatitis is caused when certain viruses infect the liver
Signs include Jaundice, liver inflammation and liver cell death
HAV (Hepatitis A Virus)
Hep Virus exceptions, Non-enveloped, single-stranded RNA (reverse transcriptase) enterovirus transmitted through contaminated food.
Causes less-severe form of hepatitis that is milder and shorter-term

34. (HBV) Hepatitis B Virus
Hepatitis B multiplies ONLY in the liver, continually supplying blood with infection
Uses reverse Transcriptase to replicate – RNA class
Incidence and risk is highest among:
Those in crowded living conditions
Drug abuse (needle-sharing)
Sexually promiscuous
Certain medical occupations involving contact with blood or blood serum
Homosexual males
Can also be transmitted via mosquitoes, birth canal, and heterosexual intercourse
Is introduced to body through break in skin or mucous membrane, or direct injection into bloodstream
A majority of infected persons do not exhibit symptoms, and eventually develop immunity
Other symptoms include malaise, fever, chills, anorexia, abdominal pain, diarrhea, fever, jaundice, rash, and

35. Adenovirus Non-enveloped, dsDNA 30 types associated with human disease
infect lymphoid tissue, respiratory and intestinal epithelia and conjuctiva
oncogenic in animals, not humans
spread by respiratory and ocular secretions
causes colds, pharyngitis, conjunctivitis, keroatoconjuctivis, acute hemorrahagic cystitis
inactivated polyvalent vaccine

36. Papillomavirus
papilloma-benign, squamous epithelial growth, wart or verruca
caused by 40 different strains of HPV
common seed warts-on fingers, etc.
plantar wart-soles of feet
genital warts-prevalent STD
transmissible through direct contact or contaminated fomites
Incubation-2 weeks to more than a year