common human diseases
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COMMON HUMAN DISEASES
A disease is an abnormal condition of an organism thatimpairs bodily functions, associated with specific symptoms and
effects. It may be caused by external factors, such as infectious
disease , or it may be of autoimmune type.
In human beings, "disease" is often used more broadly to
refer to any condition that causes pain, dysfunction, distress,
social problems, and/or death to the person afflicted, or similar
problems for those in contact with the person. In this broader
sense, it sometimes includes injuries, disabilities, disorders,
syndromes, infections, isolated symptoms.
Classification:
Classification of diseases is often done based on the mode
of transmission,symptoms and disorders caused by it.Infectious
diseases are those which are clinically evident and result from
the presence of pathogenic microbial agents, includingviruses,bacteria, fungi, protozoa, multicellular parasites, and aberrant
proteins known as
prions.Non-infectious diseases are all other
diseases, including most forms of heart diseases, genetic diseases
and sexually transmitted disesae.The non-infectious diseases are
often caused because of the impairements in the human body such
as obesity,over-weightness and abnormal gene combination
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DISEASE
Infectious disease Non-infectiousdisease
Bacteria Fungi Virus Microbes
EPIDEMIC ENDEMIC PANDEMIC
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Human diseases which are found to be deadliest worldwide are
1) Swine influenza 2) SAARS 3) POLIOMYELITIS 4)
tuberculosis.
Swineinfluenza is an infection caused in humans from
pigs. As of 2009, the known SIV strains include influenza C and
the subtypes ofinfluenza A known asH1N1
,H1N2,H3N1,H3N2,
andH2N3.
Transmission of the virus from pigs to humans is not common and
does not always lead to human influenza, often resulting only in
the production ofantibodies in the blood. If transmission does
cause human influenza, it is called zoonotic swine flu. People with
regular exposure to pigs are at increased risk of swine flu
infectionSymptoms of zoonotic swine flu in humans are similar to
those of influenza and of influenza-like illness in general, namely
chillness, fever, sore throat ,muscle pains, severe headache,coughing, weakness and general discomfort.
Classification:
Of the three genera of influenza
viruses that cause human flu,influenza a is common in pigs andInfluenza c being rare.Influenza B has not been reported in pigs.
Within influenza A and influenza C, the strains found in pigs and
humans are largelydistinct
, although because of reassortment
there have been transfers of genes among strains crossing swine,
avian, and human species boundaries.
Influenza C viruses infect both humans
and pigs, but do not infect birds.Swine influenza is known to be
caused by influenza A type. Subtypes are H1N1
,H1N2,H2N3,H3N1, andH3N2. In pigs, three influenza A virus subtypes (H1N1,
H1N2, and H3N2) are the most common strains worldwide
Transmission:
Transmission between pigs
Influenza is quite common in pigs, with
about half of breeding pigs having been exposed to the virus
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worldwide.The main route of transmission is through direct
contact between infected and uninfected animals. These close
contacts are particularly common during animal transport.
Intensive farming may also increase therisk of transmission
, as the pigs are raised in very close proximity
to each other. The direct transfer of the virus probably occurs
either by pigs touching noses, or through dried mucus. Airborne
transmission through the aerosols produced by pigs coughing or
sneezing are also an important means of infection.This happens
within days of infection.
Transmission to humans People who work with poultry and
swine, especially people with intense exposures, are at increased
risk of zoonotic infection with influenza virus endemic in these
animals, and constitute a population of human hosts in which
zoonosis and reassortment can co-occur. Vaccination of these
persons is therfore an essentiality.
Interaction with avian H5N1 in pigs
Pigs are unusual as they can be infected with influenza
strains that usually infect three different species: pigs, birds and
humans. This makes pigs a host where influenza viruses might
exchange genes, producing new and dangerous strains
Main symptoms of swine flu :
In humans
Direct transmission of a swine flu virus from pigs to humans
is occasionally possible (called zoonotic swine flu). Generally this
disease occurs when agent is less immune or occurs along as
secondary infection.
In swine
In pigs influenza infection producesfever, lethargy, difficulty
in breathingand decreased appetite.In some cases the infection
can cause abortion. Although mortality is usually low (around 1
4%), the virus can produce weight loss and poor growth, causing
economic loss to farmers. Infected pigs can lose up to 12 pounds
of body weight over a 3 to 4 week period.
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Prevention:
Prevention of swine influenza has three components:prevention in swine, prevention of transmission to humans,
and prevention of its spread among humans.
In swine
Methods of preventing the spread of influenza among swine
include facility management, herd management, and vaccination.
Because much of the illness and death associated with swine flu
involves secondary infection.Facility management includes usingdisinfectants and ambient temperature to control virus in the
environment. The virus is unlikely to survive outside living cells for
more than two weeks, except in cold (but above freezing)
conditions, and it is readily inactivated by disinfectants.Herd
management includes not adding pigs carrying influenza to herds
that have not been exposed to the virus. The virus survives in
healthy carrier pigs for up to 3 months.Prevention mainly involves
culling of infected animals and isolation of infected humans.
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In humans
Prevention of pig to human transmission Although strains of swine influenza are usually not able to
infect humans, farmers and veterinarians areencouraged to use a face mask when dealing with
infected animals. The use of vaccines on swine to
prevent their infection is a major method of
limitingswine to human transmission.
Prevention of human to human transmission
Influenza spreads between humans through coughing or
sneezing and people touching something with the virus on it andthen touching their own nose or mouth. virus is not transmitted
through food.Thermal imaging, camera & screen, photography
are used for detecting pateints . Thermal imaging can detect
elevated body temperature, one of the signs of the virusN1H1
(Swine influenza )in airports.Social distancingis another tactic.
Severe Acute Respiratory Syndrome (SAARS)is arespiratory disease in humans which is caused by the SARS
coronavirus (SARS-CoV).But, SAARS is claimed tobe eradicated
as vaccine isHowever, SARS is not claimed to have been
eradicated (unlikesmallpox
), as it may still be present in itsnatural host reservoirs (animal populations) and may potentially
return into the human population in the future.
. SARS CORONAVIRUS:
Coronaviruses arepositive-strand
, envelopedRNA viruses
that are importantpathogens of mammals and birds. This group of
viruses cause enteric or respiratory tract infections in a variety ofanimals including humans, livestock and pets.
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Signs and symptoms
Initial symptoms are flu-like and may include:fever
,
myalgia, lethargy,gastrointestinalsymptoms, cough,sore throat
and other non-specific symptoms. The only symptom that is
common to all patients appears to be a fever above 38 C(100.4
F). Shortness of breath may occur later.
DIAGNOSIS:
A chest x-ray showing increased opacity in both lungs,
indicative of pneumonia, in a patient with SARS.
SARS may be suspected in a patient who has:
1)Any of the symptoms, including a fever of 38 C (100.4 F) or
higher, and
2) Contact with someone with a diagnosis of SARS within the last
10 days and travel to region where SAARS is in abundance.
Treatment
Antibiotics are ineffective as SARS is a viral disease.
Treatment of SARS so far has been largely supportive with
antipyretics, supplemental oxygen and ventilatory support as
needed.Suspected cases of SARS must be isolated, preferably in
negative pressure rooms, with complete barrier nursing
precautions taken for any necessary contact with these patients...
Currently , Corticosteroids and Ribavirin are the most common
drugs used for treatment of SARS
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Poliomyelitis, often called polio orinfantile paralysis, is an
acute viral infectious disease spread from person to person,
primarily via the fecal-oral route. Although around 90% of polio
infections cause no symptoms at all, affected individuals can
exhibit a range of symptoms if the virus enters the blood stream.
Different types of paralysis may occur, depending on the nerves
involved. Spinal polio is the most common form, characterized by
asymmetric paralysis that most often involves the legs. Bulbar
polio leads to weakness of muscles innervated by cranial nerves.
Bulbospinal polio is a combination of bulbar and spinal paralysis.
Poliovirus was identified in 1908 by Karl Landsteiner.By
1910, much of the world experienced a dramatic increase in polio
cases .This led to discover of a new vaccine for polio.
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POLIO LIFE CYCLE
Cause
Poliomyelitis is caused by infection with a member of the
genusEnterovirus known aspoliovirus (PV). This group ofRNA
viruses prefers to inhabit thegastrointestinal tract. There are three
types of serotypes and PV causes disease in humans
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alone..Individuals who are exposed to the virus, either through
infection or by immunization with polio vaccine, develop
immunity. Infection or vaccination with one serotype of poliovirus
does not provide immunity against the other serotypes, and full
immunity requires exposure to each serotype.
Transmission:
Poliomyelitis is highly contagious and spreads easily by
human-to-human contact. In endemic areas, wild polioviruses can
infect virtually the entire human population. Virus particles are
excreted in the faeces for several weeks following initial infectionin the host. The disease is transmitted primarily via the fecal-oral
route, by ingesting contaminated food or water. It is occasionally
transmitted via the oral-oral route, a mode especially visible in
areas with good sanitation and hygiene. . Although the virus can
cross the placenta during pregnancy, the fetus does not appear to
be affected by either maternal infection or polio vaccination.
Paralytic polio: Paralysis generally develops one to ten daysafter early symptoms begin, progresses for two to three days,
and is usually complete by the time the fever breaks.
Spinal polio: Spinal polio is the most common form ofparalytic poliomyelitis; it results from viral invasion of the
motor neurons. With the destruction of nerve cells, themuscles no longer receive signals from the brain or spinal
cord and finally completely paralyzed.Progression to
maximum paralysis is rapid (two to four days), and is
usually associated with fever and muscle pain.
Bulbar polio: Making up about 2% of cases of paralytic polio,bulbar polio occurs when poliovirus invades and destroys
nerves within the bulbar region of the brain stem. Thebulbar region is a white matter pathway that connects the
cerebral cortex to the brain stem producing symptoms of
encephalitis, and causes difficulty breathing, speaking and
swallowing
Bulbospinal Polio: Approximately 19% of all paralytic poliocases have both bulbar and spinal symptoms; this subtype is called
respiratory polio or bulbospinal polio. It can lead to paralysis of
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the arms and legs and may also affect swallowing and heart
functions.
Diagnosis
Paralytic poliomyelitis may be clinically suspected inindividuals experiencing acute onset of flaccid paralysis in one or
more limbs with decreased or absent tendon reflexes in the
affected limbs
PREVENTIONPassive immunization
In 1950, William Hammon purified the gamma globulincomponent of the blood plasma of polio survivors. He proposed
that the gamma globulin, which contained antibodies to poliovirus,
could be used to halt poliovirus infection, prevent disease, and
reduce the severity of disease in other patients who had contracted
polio..
Vaccine
Two types of vaccines are used throughout the world tocombat polio. Both types induce immunity to polio, efficiently
blocking person-to-person transmission of wild poliovirus, thereby
protecting both individual vaccine recipientsand the wider
community (so-called herd immunity).
The Salk vaccine, or inactivated poliovirus vaccine (IPV), is
based on poliovirus grown in a type of monkey kidney tissue
culture, which is chemically inactivated with formalin. After twodoses of IPV (given by injection), 90% or more of individuals
develop protective antibody to all three serotypes of poliovirus,
and at least 99% are immune to poliovirus following three doses .
Vaccine produces excellent immunity in the intestine (which helps
prevent infection with wild virus in areas where it is endemic.
Tuberculosis orTB (short for TubercleBacillus
) is a
common and often deadly infectious disease caused by
mycobacteria
, usually Mycobacterium tuberculosis in humans.
Tuberculosis usually attacks the lungs but can also affect other
parts of the body. It is spread through the air, when people who
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have the disease cough, sneeze, or spit. If left untreated, kills more
than 50% of its victims.
SIGNS AND SYMPTOMS
The classic symptoms are a chronic cough with blood-tinged
sputum,
fever
, night sweats
, andweight loss. Infection of other
organs causes a wide range of symptoms.Diagnosis: relies onradiology (commonly chest X-rays), a tuberculin skin test, blood
tests, as well as microscopic examination and microbiological
culture of bodily fluids.
TransmissionWhen people suffering from active pulmonary TB cough,
sneeze, speak, or spit, they expel infectious aerosol droplets 0.5 to
5 m in diameter.A single sneeze can release up to 40,000
droplets. Each one of these droplets may transmit the disease,
since the infectious dose of tuberculosis is very low and inhaling
less than ten bacteria may cause an infection. People with
prolonged, frequent, or intense contact are at particularly high
risk of becoming infected, with an estimated 22% infection rate. Aperson with active but untreated tuberculosis can infect 1015
other people per year. Transmission can only occur from people
with active TB.The probability of transmission from one person to
another depends upon the number of infectious droplets.If
someone does become infected, then it will take at least 21 days, or
three to four weeks, before the newly infected person can transmit
the disease to others. TB can also be transmitted by eating meat
infected with TB. Mycobacterium bovis causes TB in cattle.
Causes
The primary cause of TB, Mycobacterium tuberculosis, is
a small aerobic non-motile bacillus. High lipid content of this
pathogen accounts for many of its unique clinical characteristics.
It divides every 16 to 20 hours, an extremely slow rate compared
with other bacteria, which usually divide in less than an hour. In
nature, the bacterium can grow only within the cells of a host
organism, but M. tuberculosis can be culturedin vitro.Other
known pathogenic mycobacteria include Mycobacterium leprae
,
Mycobacterium avium and M. kansasii. The last two are part of
the nontuberculous mycobacteria (NTM) group.
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Prevention
TB prevention and control takes two parallel approaches.
In the first, people with TB and their contacts are identified and
then treated. Identification of infections often involves testing high-risk groups for TB. In the second approach, children are
vaccinated to protect them from TB. No vaccine is available that
provides reliable protection for adults. However, in tropical areas
where the levels of other species of mycobacteria are high,
exposure to nontuberculous mycobacteriagives some protection
against TB.
VaccinesSeveral new vaccines to prevent TB infection are being
developed. The first recombinant tuberculosis vaccine rBCG30
which can accelerate the disappearance of bacteria as well as
protect against re-infection in mice. A very promising TB vaccine,
MVA85A
, is currently inphase II trials and is based on a
genetically modifiedvaccinia virus.
Treatment
Treatment for TB uses antibiotics to kill the bacteria.
Effective TB treatment is difficult, due to the unusual structure and
chemical composition of the mycobacterial cell wall, which makes
many antibiotics ineffective and hinders the entry of drugs. TB
requires much longer periods of treatment (around 6 to 24
months) to entirely eliminate mycobacteria from the body. Latent
TB treatment usually uses a single antibiotic, while active TBdisease is best treated with combinations of several .
The above mentioned
diseases are controlled by the discovery of vaccines but the
second phase of these diseases is possible and it will be in a larger
epidemic scale.Therefore, there is a need for a healthy
environment for a healthy life.
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