HUMAN DISEASES CAUSED BY VIRUSES

• When a cell is infected with a virus several effects may be seen.

• Many viruses cause no harm or disease but some may attack certain cells and multiply within them.

• Once mature the daughter viruses break the cell and spread elsewhere.

• If the host immunity operates effectively the virus infected cell may be killed by the host.

• Spread of virus occurs through different routes:-Skin contact- HPV (warts)Animal bite – rabiesSexually – herpes 1 & 2 , hepatitis B

• A viral disease occurs when an organism’s body is invaded by pathogenic viruses and infectious viral particles (virions) attach to and enter susceptible cells.

• Common viral diseases include :-

ChickenpoxFlu (influenza )HerpesHIV/AIDSInfectious mononucleosisMumps , measles and rubella Rabies

ACQUIRED IMMUNO DEFICIENCY SYNDROME• AIDS is a spectrum of conditions caused by infection

with the human immunodeficiency virus.

• Following initial infection , a person may experience a brief period of influenza like illness.

• This is followed by a prolonged period without symptoms.

• As infection progresses , it interfere more and more with the immune system.

• SYMPTOMS

a) Acute infection oInitial period.oIndividuals develop an influenza like illness or a

mononucleosis like illness 2-4 weeks post exposure.

oSymptoms include fever , large tender lymph nodes , throat inflammation , rash , head ache , sores of mouth.

b) Clinical latency

oAsymptomatic / chronic HIVoNear the end of this stage people experience fever , weight

loss , gastrointestinal problems and muscle pain.

c) Acquired immunodeficiency syndrome

o It is defined in terms of either a CD4+ T cell count below 200μL or occurrence of specific diseases in association with HIV infection.

oThe most common initial conditions that alert the presence are pnemocystic pneumonia ,oesophageal candidiasis .

•VIROLOGY

oHIV is a retrovirus that primarily infects components of human immune system such as CD4+ T cells , macrophages and dendritic cells.

oIt directly and indirectly destroys CD4+ T cells.

• TRANSMISSION

Unprotected sexual intercourseContaminated blood transfusions Hypodermic needlesFrom mother to child during pregnancy ,

delivery or breast feeding.Body fluids like saliva tears do not transmit HIV.

• TREATMENT

There is currently no cure or effective HIV vaccine.Treatment consists of highly active antiretroviral

therapy (HAART) which slows down the progression.

HAART:-• Combinations of at least 3 medications.• A Non-nucleoside reverse transcriptase inhibitor

(NNRTI)and two nucleoside analogue reverse transcriptase inibitor (NRTIs).

SMALLPOX

• Infectious disease caused by either of two virus variants ,Variola major and Variola minor.

• Infection is focused in small blood vessels of the skin and in the mouth and throat.

• In the skin it results in a characteristic maculopapular rash and later raised fluid- filled blisters.

• SIGNS AND SYMPTOMS

a) Ordinary• Macules(rash) raised papules fluid filled

vesicles pustules Mature fluid leaks deflate & dry up depigmented scars.

b) Modified • Less severe• Lesions fewer and evolve more quickly and may

not show typical characteristics of smallpox.

c) Malignant• Lesions remains almost flush with the skin.• Rash on tongue and palate is extensive.• Vesicles contain little fluid.

d) Hemorrhagic• Severe form.• Extensive bleeding into skin , mucous membrane

and gastrointestinal tracts.• Occurrence is mostly in adults.

•VIROLOGY

oIt is caused by the infection with variola virus.

oVirus infects only humans in nature.

• TRANSMISSIONoInhalation of airborne variola virus.oFace-to-face contact with infected person.oDirect contact with infected bodily fluids and

contaminated objects.

• TREATMENToVaccination within 3 days of exposure prevent or

lessen severity.oWound care , infection control , fluid-therapy.oAnti-viral drugcidofovir (therapeutic agent).

RABIES

• A viral disease that causes acute inflammation of brain in humans and warm-blooded animals.

• Caused by lyssaviruses including rabies virus and Australian bat lyssavirus.

• The virus travels to the brain following peripheral nerves.

• The disease can only be diagnosed after the start of symptoms.

• SYMPTOMS

oViolent movementsoUncontrolled excitementoFear of wateroInability to move body partsoConfusionoLoss of consciousness

• HYDROPHOBIA

oSet of symptoms in the later stages of disease.oThe person has difficulty swallowing , shows

panic when presented with liquids to drink and can not quench thirst.

oSalivary production is greatly increased.oAttempts to drink causes painful spasms of the

muscles in throat and larynx.

• TRANSMISSION

oMost animals can be infected by the virus and can transmit it to humans.

oInfected bats, monkeys, foxes, cattle, dogs and cats present the greatest risk to humans.

oThe route of infection is usually by a bite.oTransmission between humans is rare.

• TREATMENT

oThoroughly washing the wound as soon as possible with soap and water for 5 minutes reduce the number of viral particles.

oPovidone-iodine or alcohol is recommended further.

oOne dose of human rabies immunoglobulin(HRIG) and four doses of rabies vaccine over a 14-day period.

MEASLES

• Also known as morbilli, rubeola , red measles .

• Highly contagious disease caused by measles virus.

• It is an airborne disease which spreads through coughs and sneezes.

• It may also be spread through contact with saliva or nasal secretions.

• SYMPTOMS

oInitial symptoms include fever, cough, runny nose and red eyes.

oAfter 2-3 days small white spots may form inside the mouth known as Koplik’s spots.

oRed flat rashes starts on the face and then spreads to rest of the body.

oComplications include diarrhea, blindness, inflammation of the brain and pneumonia.

4 day measles rash

• TREATMENT

oAntibiotics for pneumonia, sinusitis and bronchitis.oIbuprofen or paracetamol for fever and pain.oFast acting medications to dilate airways for

coughing.oUse of vit A during treatment to decrease the risk

of blindness.

SWINE FLU

• Swine influenza, also called pig influenza, swine flu, hog flu and pig flu, is an infection caused by any one of several types of swine influenza viruses.

• SIV strains include influenza C and the subtypes of influenza A known as H1N1, H1N2, H2N1, H3N1, H3N2, and H2N3.

• Swine influenza virus is common throughout pig populations worldwide.

H1N1 influenza virus

• SYMPTOMS

oSymptoms include fever, sore throat, watery eyes, body aches, shortness of breath, headache, weight loss, sneezing, abdominal pain, lack of appetite and fatigue.

oThe most common cause of death is respiratory failure.

oOther causes of death are pneumonia high fever, dehydration, electrolyte imbalance and kidney failure.

• TREATMENToAntiviral drugs can make the illness milder and

make the patient feel better faster.

oBeside antivirals, supportive care at home or in a hospital focuses on controlling fevers, relieving pain and maintaining fluid balance, as well as identifying and treating any secondary infections or other medical problems.

BIRD FLU• Bird flu, or avian influenza, is a viral infection spread

from bird to bird.

• H5N1 is a highly pathogenic avian influenza (HPAI) virus.

• It is deadly to humans and to other mammals that catch the virus from birds.

• People catch bird flu by close contact with birds or bird droppings.

• SYMPTOMSofever (above 38 C or 100.4 F),ocough sore throat,omuscle achesonauseaovomitingodiarrheaoheadacheojoint painoinsomniaoeye infections.

• TREATMENTorestingodrinking plenty of fluids and eating healthily.otaking medication to help treat fever and pain,

such as aspirin and paracetamol.oOseltamivir , Zanamivir and Peramivir help reduce

the severity of the condition, prevent complications and improve the chances of survival.

SEVERE ACUTE RESPIRATORY SYNDROME (SARS)

• Viral respiratory disease caused by corona virus.• Infection causes acute

respiratory distress.• Lead to pneumonia.• Transmission is through infected

droplets spraying to air by coughing or sneezing. SARS corona virus

• TREATMENT

oAntibiotics to treat bacteria that cause pneumonia.oHigh doses of steroids to reduce swelling in lungs.oOxygen , breathing support or chest therapy.