Transcript Viral diseases - Austin Community College

Viral Diseases
Parvoviridae
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Erythrovirus is human pathogen.
Causes lace like rash that lasts a few days.
Children 4-10 yrs. old most affected.
Transmission occurs during incubation
period.
• No longer infectious by appearance of
rash.
Papovaviridae
• Papilloma virus
– Skin warts and genital warts
– Various strains of Human Papilloma Virus (HPV).
Each have preference for different body sites.
– Grouped into 2 main categories:
• 1)
• 2)
cutaneous
mucosal
– Incubation can be up to 2 years before signs or
symptoms are detected.
– Genome can persist in cells for years without outward
signs.
– Early genes stimulate proliferation of basal cells
which causes the protruding papilloma (visible tissue
or wart).
• Cutaneous (plain old warts)
– Transmission through skin abrasions
• Commonly picked up from wet floors of public
swimming pools and bathrooms
• Subsequent spreading through scratching, picking,
digging of wart.
– Rx
• Wart regresses spontaneously.
• Cryotherapy (freezing with liquid Nitrogen) or
injectible anti-cancer drugs are occasionally
effective.
• Mucosal
– Transmission through abrasions during sexual
intercourse
• Can cause cancer by inactivation tumor suppressor gene
products. The tumor suppress gene prevents the uncontrolled
growth of cells. When it’s function is compromised
uncontrolled cell growth is allowed causing tumors.
• Cervical carcinomas may develop 20-50 years post infection
because the genome of the virus persists in the infected cells.
– Rx
• Laser
• Surgery
– Vaccination: currently testing vaccine against mucosal
strains
– “On average, there are 9,710 new cases and 3,700
deaths from cervical cancer in the United States each
year.
– HPV is the most common sexually transmitted
infection in the United States, More than 20 million
men and women in the United States are currently
infected with HPV and there are 6.2 million new
infections each year. HPV is most common in young
women and men who are in their late teens and early
20s. By age 50, at least 80 percent of women will have
acquired HPV infection.
– “Although an effective vaccine is a major advance in
the prevention of genital HPV and cervical cancer, it
will not replace other prevention strategies, such as
cervical cancer screening for women or protective
sexual behaviors,” said Dr. Schuchat “Women should
continue to get pap tests as a safeguard against
cervical cancer.”’ www.cdc.gov
Herpesviridae
– 2 types of Herpes Simplex Virus
• 1) Herpes Simplex Virus 1 (HSV-1): cold sores,
shed in saliva, contaminated hands, eating utensils,
etc.
• 2) HSV-2: sexual intercourse, through infected
birth canal to infants
– Varicella Zoster, Chickenpox/Shingles: to be
covered in the group presentations.
• Signs and Symptoms
– infection causes groups of
small, painful blisters. The
fluid in the blisters may be
clear or cloudy. The area
under the blisters will be
red. The blisters break
open so easily that they
quickly become open
sores.
– It may hurt to urinate. You
may run a fever and have
other flu-like symptoms.
Transmission
– Spread by close person to person contact w/ lesions or
mucosal secretions
– Infects sensory neurons and remains for in the sensory
neurons life, causing recurrent infections.
– Initial infection is usually more severe w/ subsequent
infections decreasing in frequency, duration, and
severity.
• Prevention and Rx
– Avoid contact when lesions are present.
– Use condoms during sexual intercourse whether or not
lesions are present.
– Acyclovir
• Inhibits DNA polymerase
• Helps to further decrease the frequency and duration of
subsequent outbreaks.
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Caliciviridae
• Norwalk virus
– Responsible for most gastroenteritis cases
– Signs and symptoms:
• mild fever, nausea, vomiting, malaise, myalgia
(muscle aches)
– Transmission: Contact with infected body
fluids, fomites.
– Prevention: wash your hands frequently.
Picornaviridae
• Poliovirus: Will be discussed at a later time.
• Enteroviruses
– Commonly infect children, produce life long
immunity
– Can cause meningitis, carditis, rashes (very common),
sometimes colds or sore throats during summer, as
well as other types of disease.
– Transmitted mainly by close contact via fecal-oral
route, droplet spread can also occur.
• Rhinoviruses
– Over 100 different rhinoviruses, which cause 50% of
all colds
– No possibility for vaccine yet
– 3 or 4 rhinovirus types circulate among community
simultaneously.
– Virus shed in nasal secretions for 2-3 days.
• Transmission
– Spread through sneezing, coughing, contamination of
hands, handkerchiefs, any other fomites, to nose or
eye.
– Because generally acquire cold during cold weather,
has generated myth that if exposed to cold weather
will get a cold. Remember that it is the organism that
causes the cold, not the weather or how little clothing
one is wearing. However, the weather and clothing
can be predisposing factors for acquiring an illness.
• Hepatitis A
– Similar symptoms to Hepatitis B
• Preicteric phase: malaise, anorexia, nausea, and lethargy
aren’t as bad, don’t last as long
• Icteric phase: Hepatomegaly may produce pain in the right
upper abdominal quadrant, followed by bilirubinuria, then
pale feces and jaundice.
• Convalescent phase: signs and symptoms decrease, virus is
eliminated from body.
– Transmission
• Oral-Fecal route. Virused passed in the feces of an infected
person. It is transmitted when an infected individual fails to
wash his hands after going to the bathroom, etc.
• Multiplies in intestinal cells before entering blood stream and
infecting liver
• Incubation period is about 4 weeks
• Most infections occur in children (usually
subclinical)
• Illness usually last 4 weeks
– Rx and prevention
• Good public and personal hygiene
• Vaccine for children, especially those exposed to
other children on a daily basis such as in daycare
Orthomyxoviridae
• Influenza
– Signs and symptoms
• Fever, sore throat, nonproductive cough, myalgia,
headache, and malaise
• Lasts 3-7 days
• Complications depend on age of patient
– Possible pneumonia, middle ear infection, croup
– Susceptible to secondary bacterial infections
• Transmission
– Droplet (sneezing and coughing)
– Short incubation period (1-4 days)
– Antigens frequently mutate causing new strains, this is
called an antigenic shift.
– Influenza Type A undergoes an antigenic shift every
10-40 years.
– Flu season is generally Oct. to Mar each year.
– Note: The vaccine given to infants called
Hemophilus influenzae is not the same as the flu
vaccine. The bacteria mentioned above causes
meningitis, not influenza.
• Vaccine
– Develop according to prevalent strain in other part
of world
– Recommend that elderly and under 2 receive vaccine
as well as those more likely to be exposed such as
care givers of young children.
– The vaccine is made according to the strains that
affect the other side of the world when it is not our
flu season. The most prevalent strains are then used
to manufacture the virus for our flu season.
– If the strain mutates or if a new strain is introduced
into the population after the virus has been
manufactured, the vaccine probably won’t provide
adequate protection against all strains of the virus.
– Each year a new flu vaccine is recommended
because the strains change from year to year.
Paramyxoviridae
• Measles
– highly contagious, characterized by a fever, cough, conjunctivitis
(redness and irritation in membranes of the eyes), and spreading
rash.
– Symptoms
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tiny white spots inside the mouth (called Koplik's spots)
photophobia (light sensitivity)
Rash, appears around the fifth day of the disease
Rash may last 4 to 7 days
The rash usually starts on the head and spreads to other areas,
progressing downward
Koplik’s spots
• Transmission
– The infection is spread by contact with droplets from the
nose, mouth, or throat of an infected person.
– The incubation period is 8 to 12 days before symptoms
generally appear.
• Common Complications
– Croup, bronchitis, bronchopneumonia (bacterial pneumonia
most common cause of death in malnourished children)
• Treatment
– There is no specific treatment of measles, though
some children may require supplementation with
Vitamin A.
– Symptomatic relief may be achieved with bed rest,
acetaminophen, and humidified air
– Prevent through vaccination
• Mumps
– Signs and Symptoms
 Swollen, painful salivary glands on one or both sides of
the face
 Pain with chewing or swallowing, especially sour foods
or beverages that promote saliva production
 Fever
 Weakness and fatigue
 Tenderness and swelling of a testicle (orchitis)
• Transmission
– saliva and respiratory secretions
• Treatment
– Like most viral illnesses, mumps infection
must simply run its course. Fortunately, most
children and adults recover from an
uncomplicated case of mumps within 2 weeks'
time.
• Prevention
– vaccination
• RSV (Respiratory Syncytial Virus)
– Transmission
• Highly contagious
• Shed in respiratory secretions for several days, sometimes
weeks
• Incubation period is 4-5 days
• Very severe in young infants, can cause death.
– Signs and Symptoms
• Most common manifestation is febrile rhinitis and/or
pharyngitis
• Virus multiplies in mucous membranes of the nose and throat
• Fatal cases show extensive bronchiolitis and pneumonitis
– Can cause impaired lung function for years
and recurrent bouts of asthma
– Infants can die due to difficulty breathing.
– Vaccine is available but it only helps in
recovery, not in avoiding disease.
Coronaviridae
• SARS
– “According to the World Health Organization
(WHO), a total of 8,098 people worldwide
became sick with SARS during the 2003
outbreak. Of these, 774 died. In the United
States, only eight people had laboratory
evidence of SARS-CoV infection. All of these
people had traveled to other parts of the world
with SARS. SARS did not spread more widely
in the community in the United States.”
• www.cdc.gov
– Symptoms: “In general, SARS begins with a
high fever (temperature greater than 100.4°F
[>38.0°C]). Other symptoms may include
headache, an overall feeling of discomfort, and
body aches. Some people also have mild
respiratory symptoms at the outset. About 10
percent to 20 percent of patients have diarrhea.
After 2 to 7 days, SARS patients may develop
a dry cough. Most patients develop
pneumonia.”
• www.cdc.gov
– Transmission: “The virus that causes SARS is
thought to be transmitted most readily by respiratory
droplets (droplet spread) produced when an infected
person coughs or sneezes. Droplet spread can happen
when droplets from the cough or sneeze of an infected
person are propelled a short distance (generally up to 3
feet) through the air and deposited on the mucous
membranes of the mouth, nose, or eyes of persons
who are nearby. The virus also can spread when a
person touches a surface or object contaminated with
infectious droplets and then touches his or her mouth,
nose, or eye(s). In addition, it is possible that the
SARS virus might spread more broadly through the air
(airborne spread) or by other ways that are not now
known.”
• www.cdc.gov
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“SARS is clearly spread by droplet contact. When someone with SARS
coughs or sneezes, infected droplets are sprayed into the air. Like other
coronaviruses, the SARS virus may live on hands, tissues, and other surfaces
for up to 6 hours in these droplets and up to 3 hours after the droplets have
dried.
While droplet transmission through close contact was responsible for most of
the early cases of SARS, evidence began to mount that SARS might also
spread by hands and other objects the droplets had touched. Airborne
transmission was a real possibility in some cases. Live virus had even been
found in the stool of people with SARS, where it has been shown to live for
up to four days. And the virus may be able to live for months or years when
the temperature is below freezing.
With other coronaviruses, re-infection is common. Preliminary reports
suggest that this may also be the case with SARS.
Preliminary estimates are that the incubation period is usually between 2 and
10 days, although there have been documented cases where the onset of
illness was considerably faster or slower. People with active symptoms of
illness are clearly contagious, but it is not known how long contagiousness
may begin before symptoms appear or how long contagiousness might linger
after the symptoms have disappeared.
Reports of possible relapse in patients who have been treated and released
from the hospital raise concerns about the length of time individuals can
harbor the virus.”
– www.nlm.nih.gov/medlineplus
• Treatment: People suspected of having SARS
should be evaluated immediately by a physician
and hospitalized under isolation if they meet the
definition of a suspected or probable case.
• Antibiotics are sometimes given in an attempt to
treat bacterial causes of atypical pneumonia.
Antiviral medications have also been used. High
doses of steroids have been employed to reduce
lung inflammation. In some serious cases, serum
from people who have already gotten well from
SARS (convalescent serum) has been given.
Evidence of general benefit of these treatments
has been inconclusive.
• Other supportive care such as supplemental
oxygen, chest physiotherapy, or mechanical
ventilation is sometimes needed.
• Prevention: Minimizing contact with people with SARS minimizes
the risk of the disease. This might include minimizing travel to
locations where there is an uncontrolled outbreak. Where possible,
direct contact with people with SARS should be avoided until at least
10 days after the fever and other symptoms are gone.
• The CDC has identified hand hygiene as the cornerstone of SARS
prevention. This might include hand washing or cleaning hands with
an alcohol-based instant hand sanitizer.
• People should be taught to cover the mouth and nose when sneezing
or coughing. Respiratory secretions should be considered to be
infectious, which means no sharing of food, drink, or utensils.
Commonly touched surfaces can be cleaned with an EPA approved
disinfectant.
• In some situations, appropriate masks and goggles may be useful for
preventing airborne or droplet spread. Gloves might be used in
handling potentially infectious secretions.
Flaviviridae
• West Nile Encephalitis
– “West Nile virus is transmitted by mosquitos
and causes an illness that ranges from mild to
severe. Mild, flu-like illness is often called
West Nile fever. More severe forms of disease,
which can be life-threatening, may be called
West Nile encephalitis or West Nile
meningitis, depending on where it spreads.”
• www.nlm.nih.gov/medlineplus
• “West Nile virus was first identified in 1937 in the West
Nile region of Uganda, in eastern Africa. It was first
identified in the US in the summer of 1999 in the Queens
borough of New York, NY. It caused 62 cases of
encephalitis and 7 deaths that summer. Since 1999 the
virus has spread throughout the continental US and as of
July 2004 has been identified in 46 states.
• Mosquitos carry the highest amounts of virus in the early
fall, thus there is a peak of disease in late August-early
September. The risk of disease then decreases as the
weather becomes colder and mosquitos die off.
• Although many people are bitten by mosquitos that carry
West Nile virus, most do not know they've been exposed.
Few people develop severe disease or even notice any
symptoms at all.”
– www.nlm.nih.gov/medlineplus
• Symptoms:
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Fever
Headache
Back pain
Muscle aches
Lack of appetite
Sore throat
Nausea
Vomiting
Abdominal pain
Diarrhea
These symptoms usually last for 3 to 6 days.
With more severe disease, the following symptoms can also be
seen and require prompt attention:
Muscle weakness
Stiff neck
Confusion or change in clarity of thinking
Loss of consciousness
• www.nlm.nih.gov/medlineplus
• Diagnosis: “The most accurate way to diagnose this
infection is serology, a test to detect the presence of
antibodies against West Nile virus in CSF or serum (a
blood component). This is considered the gold standard
for diagnosis.” www.nlm.nih.gov/medlineplus
• Treatment: “Because this illness is not caused by
bacteria, antibiotics do not help treat West Nile virus
infection. Standard hospital care may help decrease the
risk of complications in severe illness. There is no human
vaccine available at present, and it is likely there will not
be one for several years.
• Research trials are under way to determine whether
ribavirin, an antiviral drug used to treat hepatitis C, may
be helpful.”
– www.nlm.nih.gov/medlineplus
• Prevention: “The best way to prevent West Nile
virus infection is to avoid mosquito bites. Using
mosquito-repellant products containing DEET
and wearing long sleeves and pants are the most
effective way to avoid bites. Community
spraying for mosquitos may also prevent
mosquito breeding.
• Mosquitos breed in stagnant water. If you notice
pools of standing water -- even in small areas
such as trash bins and plant saucers -- drain them
promptly.
• Testing of donated blood and organs is currently
being evaluated. There are no guidelines at
present.”
– www.nlm.nih.gov/medlineplus
Rabdoviridae
• Rabies-addressed a later time.
Retroviridae
• HIV/AIDS
• See Fig. 20.21 for the viral replication strategy.
– The most important thing to understand about HIV is
that it can hide out in the host cell chromosomes for
extended periods of time. When the conditions are
right, the virus will begin the viral replication cycle,
make and release virions.
• HIV is not AIDS
• AIDS is when the provirus becomes an active
virus, destroying T-helper cells of the immune
system, thus compromising the immune system.
• Transmission:
• “HIV is spread by sexual contact with an infected person,
by sharing needles and/or syringes (primarily for drug
injection) with someone who is infected, or, less
commonly (and now very rarely in countries where blood
is screened for HIV antibodies), through transfusions of
infected blood or blood clotting factors. Babies born to
HIV-infected women may become infected before or
during birth or through breast-feeding after birth.
• In the health care setting, workers have been infected
with HIV after being stuck with needles containing HIVinfected blood or, less frequently, after infected blood gets
into a worker’s open cut or a mucous membrane (for
example, the eyes or inside of the nose). There has been
only one instance of patients being infected by a health
care worker in the United States; this involved HIV
transmission from one infected dentist to six patients.”
– www.cdc.gov
• Prevention:
• “Gloves should be worn during contact with blood or
other body fluids that could possibly contain visible
blood, such as urine, feces, or vomit.
• Cuts, sores, or breaks on both the care giver’s and
patient’s exposed skin should be covered with bandages.
• Hands and other parts of the body should be washed
immediately after contact with blood or other body fluids,
and surfaces soiled with blood should be disinfected
appropriately.
• Practices that increase the likelihood of blood contact,
such as sharing of razors and toothbrushes, should be
avoided.
• Needles and other sharp instruments should be used only
when medically necessary and handled according to
recommendations for health-care settings. (Do not put
caps back on needles by hand or remove needles from
syringes. Dispose of needles in puncture-proof containers
out of the reach of children and visitors.)”
– www.cdc.gov
• “Condoms are classified as medical devices and
are regulated by the Food and Drug
Administration (FDA). Condom manufacturers in
the United States test each latex condom for
defects, including holes, before it is packaged.
The proper and consistent use of latex or
polyurethane (a type of plastic) condoms when
engaging in sexual intercourse--vaginal, anal, or
oral--can greatly reduce a person’s risk of
acquiring or transmitting sexually transmitted
diseases, including HIV infection.”
– www.cdc.gov
• Perinatal HIV Transmission
– “Accounts for nearly all pediatric AIDS cases. HIV
transmission from mother to child during pregnancy, labor and
delivery or by breast feeding accounted for approximately 91%
of all AIDS cases reported among U.S. children between 1985
and 2004 (1).
– Can be prevented. Data indicate that when appropriate
antiretroviral medications are given during pregnancy, labor and
delivery and after birth, the risk of transmission can be reduced to
less than 2% (2) compared with approximately 25% when no
interventions are given (3).”
– www.cdc.gov
• Vaccine: a vaccine is still years away. It is difficult to
develop a vaccine for HIV because it is constantly
mutating.
• Be sure to read more about HIV and AIDS in your
textbook, pgs. 636-645,
• Treatment:
– Reverse Transcriptase Inhibitors-block the action of
reverse transcriptase preventing the production of viral
DNA and insertion into the host chromosomes.
– Protease Inhibitors-inhibit the final assembly and
maturation of viral particles.
– Fusion Inhibitors-block the virus from fusing the with
the host cell membrane.
– Integrase Inhibitors-block the integration of the viral
DNA into the host cell chromosome.
– Usually one or more of these types of drugs are used
at the same time.
• Drug treatments seem to be more effective in combination
with each other.
Prions and Viroids
• Creutzfeldt-Jakob: prion disease
– Prions are infectious proteins. It is not well understood where
these proteins come from however there is some evidence that
some prions begin as normal proteins made by the body, that
mutate into an infectious form.
– The most common form of classic CJD is believed to occur
sporadically, caused by the spontaneous transformation of normal
prion proteins into abnormal prions. This sporadic disease occurs
worldwide, including the United States, at a rate of
approximately one case per 1 million population per year,
although rates of up to two cases per million are not unusual. The
risk of CJD increases with age, and in persons aged over 50 years
of age, the annual rate is approximately 3.4 cases per million. In
recent years, the United States has reported fewer than 300 cases
of CJD a year.
• New variant Creutzfeldt-Jakob disease (vCJD) is
an infectious form of CJD that is related to "mad
cow disease" (bovine spongiform encephalitis
). The agent responsible for mad cow disease is
believed to be the same agent responsible for
vCJD in humans. This type of CJD was first
described in 1996 in the United Kingdom.
• New variant Creutzfeldt-Jacob disease accounts
for less than 1% of cases, and tends to affect
younger people. New variant CJD can result
when someone is exposed to contaminated
products.
• Once symptoms appear, the disorder progresses
rapidly and may be confused with other types of
dementia -- like Alzheimer's disease. Both forms
of CJD, however, are distinguished by extremely
rapid progression from onset of symptoms to
disability and death. Early symptoms include
personality changes and difficulty with
coordination.
• Creutzfeldt-Jakob disease may be related to
several other diseases also thought to be caused
by prions, including kuru (seen in New Guinea
women who ate the brains of deceased relatives
as part of a funerary ritual), scrapie (found in
sheep), and other rare human diseases, such as
Gerstmann-Straussler-Scheinker disease and fatal
familial insomnia.
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Personality changes
Hallucinations
Muscle twitching
Muscle stiffness
Nervous, jumpy feelings
Changes in gait (walking, locomotion)
Lack of coordination -- stumbling, falls
Speech impairment
Poor enunciation (hard-to-understand speech or mumbling)
Sleepiness
Delirium or dementia develops rapidly
• Deterioration in all aspects of brain function
• Profound confusion, disorientation
– Additional symptoms that may be associated with this
disease:
– Memory loss
– Anxiety, stress, and tension
• Treatment: There is no known cure for Creutzfeldt-Jakob disease.
Custodial care may be required early in the course of the disease.
Medications may be needed to control aggressive behaviors. These
include sedatives, antipsychotics, and others.
• The need to provide a safe environment, control aggressive or
agitated behavior, and meet physiologic needs may require
monitoring and assistance in the home or in an institutionalized
setting. Family counseling may help in coping with the changes
required for home care.
• Visiting nurses or aides, volunteer services, homemakers, adult
protective services, and other community resources may be helpful in
caring for the person with Creutzfeldt-Jakob disease.
• Behavior modification may be helpful, in some cases, for controlling
unacceptable or dangerous behaviors. This consists of rewarding
appropriate or positive behaviors and ignoring inappropriate
behaviors (within the bounds of safety). Reality orientation, with
repeated reinforcement of environmental and other cues, may help
reduce disorientation.
• Legal advice may be appropriate early in the course of the
disorder, to form advance directives, power of attorney,
and other legal actions that may make it easier to make
ethical decisions regarding the care of an individual with
Creutzfeldt-Jakob disease.
• Expectations (prognosis)
• The outcome is usually very poor. Complete dementia
commonly occurs within 6 months or less of the onset of
symptoms, with the person becoming totally incapable of
self-care.
• The disorder is fatal in a short time, usually within 7
months, but a few people survive as long as 1 or 2 years
after diagnosis of the disorder. The cause of death is
usually infection, heart failure, or respiratory failure.
Sources
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http://www.cdc.gov
http://www.nlm.nih.gov/medlineplus/
Fenner, F.J. and White, O.J., eds. (1994).
“Medical Virology” 4th Ed. Academic Press,
Inc., San Diego, California.
Case, C.L., Funke, B.R. andTortora, G. J., eds.
(2001). “Microbiology: An Introduction” 7th
Ed. Benjamin Cummings.