POX VIRUS
Introduction
Pox
viruses are largest sized complex DNA viruses belonging the family pox
viridiae, that replicate entirely in the cytoplasm of vertebrate or
invertebrate cells. Clinically important pox viruses include Variolla
vaccinia and varicella. Variola is distinguished from varicella in causing
the infection, variolla causes small pox, which is characterized by the fever
develops before the appearance rash while varicella causing chicken
pox developed with fever and rash
simultaneously, vaccine is also called cowpox virus which is
closely related to variola, it cause the mild eruptive disease in cows
nevertheless it produces immunity to the small pox infection when it is
transmitted to healthy humans, The word vaccinia is sometimes used
interchangeably with cowpox to refer to the human from of the disease,
sometimes to refer only to the artificially induced human from of cowpox.
Moreover the members of
General characters:
Usually
it is a double – stranded DNA orthopox virus. It causes highly contagious
disease called small pox. Approximately more than 500 million people
were killed in the 20th century due to this infection. In United
States, 300 million people were affected. Transmission occurs mainly through
the inhalation of respiratory droplets ( formed by coughing and sneezing )from
infected individuals. Moreover it can be spread through fomites, which are scab
contaminated materials such as bedding and clothing, smallpox only infects
human and cannot survive for more than a few months outside its host under the
most optimal conditions. As it exponentially spreading the disease, it seems to
be an effective bioweapon, it can be stable for hours as an aerosol (
over 24 hours in optimal environmental conditions )and can be produced and
stored in large quantities .The soviet union produced tons of weaponized
variola major per year during cold war, in violation of the 1975 Biological
Weapons Convention.
Morphology :
It is an enveloped
virus. Inner, core is present. The core of the virus is dumbbell- shaped;
meaning the middle of the core is narrower than the ends. The core contains the viral double- stranded
DNA and proteins needed to help uncoat the virus core and replicate the virus.
The specific structure of the smallpox virus will vary based on whether it is
inside the cell, outside the cell, or attached to the cell’s surface.
Virulent Factors:
Virulence factors make an organism
dangerous. This organism has two virulence factors namely SPICE ( Smallpox Inhibitor of Complement Enzymes ), CKBP-II ( secreted chemokine-
binding protein, type 2.)
Spice:
It enables the virus evade
mechanism, it proteins the virus from the attack of human immune cells. It
inactivates machinery of host immune system.
CKBP-II :
The second known
virulence factor, CKBP-II ( secreted Chemokine-Binding
Protein, type 2),blocks signals that cell for more immune cells and promote
inflammation at the site of infection.
Pathogenesis
:-
Source
·
Patient
·
Nasal
secretions
·
Infected
droplets, scabs
Symptoms:
Symptoms, including
headache, high fever, malaise and fatigue, begin approximately 12 days after
exposure to infection.
Enantham rash :
It is an
important features of infection that appears on the infected individual’s mucus
membranes (the inside of the mouth, nose
and throat )initially. Later, it appears all over the body, with higher
concentrations of lesions on the face, arms and legs, this classic pox lesions
are firm umbilicated ( indented in the
center ),and progress together through the stage of lesion development (
maculopapular rash , vesicles, pustules, scabs, scars, ). After 8-9days of the
rash, the smallpox pustules start to develop scab over and fall off.
Individuals are less contagious at this stage nevertheless continue to be
contagious until the last scab has fallen off. Hence permanent scars,
blindness, and arthritis can be resulted. However, the lesions are hemorrhagic,
characterized by bleeding sores, or flat, where the lesions are soft and flat.
The mortality rates for these types of infections are over 95%.
Treatment:
Treatment remains largely experimental. Injection
with Vaccinia Immunoglobulin (VIG), antibodies produced against the vaccinia
virus, may help alleviate some symptoms. The antiviral medication cidofovir may
be used in emergency situations, and ST-246, a new and promising smallpox
antiviral , is currently undergoing phase I clinical trials. In the addition to
other supportive care, antibiotics are given to reduce potential secondary
bacterial infections. Vaccination after exposure to smallpox is protective if given
sufficiently early.
Prevention :
In 1796,
Edward Jenner developed the first
vaccine against smallpox using material that contained the cowpox virus. The
modern smallpox vaccine contains Vaccinia virus, (unrelated to the cowpox
virus) is administered chickenpox is a highly contagious disease caused by the
varicella-zoster virus (VZV ). It is a DNA virus and is belonging to the family
her-pes virus. Primary infections with VZV result in chickenpox. The virus is
believed to have a short survival time in the environment. However chickenpox
can be serious in babies, adults and people with weakened immune system.
Varicella is a relative of the herpes
virus and is present through out the world. Its highly infectious.
Pathogenesis
Mode of
transmission: Touching the skin of someone with an active rash or Sneezing or coughing
touching by touching the infected person it spreads from one person to
another person.
Sneezing
or coughing: While
sneezing or coughing the droplet comes out, that spreads in the air and initiating
to develop the infection.
Reinfection:
Moreover, this virus responsible for causing
reinfection following the primary infection; it is occurring in 10-20% of the
individuals. In this, virus remains latent in the cerebral or posterior root
ganglia for several decades even after recovery. Then the virus is reactivated
in the ganglion and tracks down the sensory nerve to the area of the skin
innervated by the nerve, producing a varicella from rash in the distribution of
a dermatome. The failure of the host defense mechanisms to contain the
virus in the ganglia after such prolonged periods of times is not understood
however, in immune competent individuals, it is probably due to the decline
effectiveness of previously acquired immunity with advancing age. Herpes zoster
also appears in increasing frequency in immunocompromised individuals such as
those with Hodgkin’s disease and AIDS, who have effective CMI. Also
disseminated herpes zoster is more likely to occur in such people.
Chickenpox
is a highly contagious infection characterized by an itchy rash made up of red,
fluid-filled blisters (pox) and flu like symptoms. Both the rash and the other
symptoms usually can be effectively treated with over- the counter medication
and home remedies, through an antiviral drug may be prescribed. Once regarded as an inevitable disease of
childhood, chickenpox has become less common since the advent of the chickenpox
vaccine. Through an initial bout of chickenpox usually resolves in a few days
or weeks, the virus that causes chickenpox never leaves the body and can
re-emerge after decades to trigger a painful illness that are called shingles in order adults.
Symptoms:
The most distinctive
is the telltale rash, which is occurs about 14days from exposure. Made up hundreds
of red, fluid-filled blisters, the chickenpox rash first shows up the face,
scalp, and torso, and then spreads to the arms and legs. Because chickenpox is
a viral infection, it also causes a cluster of symptoms similar to the flu,
including mild fever, headache, abdominal pain, fatigue, swollen glands, and
overall malaise. Adults who come down with chickenpox tend to experience these
symptoms first and then rash would develop. Children often get the spots first.
“Breakthrough cases,” those that occur despite vaccination against chickenpox,
are usually milder and, in particular, have fewer rashes.
Complications
from the chickenpox infections aren’t common, and are more likely to occur in
adults than children, but they can be serious. Some possible secondary problems
caused by chickenpox include skin infection, and Reye’s syndrome (related to
aspirin use in children).
Lab diagnosis:
It can be diagnosed based on the history of viral symptoms
and the characteristic appearance of the rash, because, sometimes the
chickenpox rash can be confused with herpes simples, impetigo, insect bites or
scabies. If there’s any question that rash is the result of chickenpox, a viral
culture can be taken. However, it can take longer to get the results than for
the illness to resolve.
Treatment:
A non-steroidal anti-inflammatory drug (NSAID) such as
ibuprofen or acetaminophen can help bring down a fever and ease headaches and
general discomfort.
Dealing with the rash can be more challenging, especially
when it comes to a small child who has a hard time not scratching their skin.
Fortunately, there are lots of options, including: Soaking in a tube of warm
water mixed with colloidal.
Applying calamine lotion directly to bother-some blisters.
Oral antihistamines such as Benadry1 (diphenhydramine).
It’s also vital to keep kids’ fingernails short and very
clean.
Sometimes it’s necessary to treat people who are at risk of
becoming seriously ill from chickenpox, such as those with compromised immune
systems. For example, an antiviral medication called VariZIG ( varicella zoster immune globulin ) may be
used.
Prevention:
Stay away and keep the children away from anyone who has
chickenpox. Varicella vaccine can be given with the exception of certain
individuals such as pregnant women, however kids also usually advised to get
the varicella vaccine.
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