2. 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 – rabies
Sexually – herpes 1 & 2 , hepatitis B, AIDS.
• 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.
4. 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.
HIV 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.
SYMPTOMS
a) Acute infection : Individuals develop an influenza like
illness or a mononucleosis like illness 2-4 weeks post
exposure.
b) Symptoms include fever , large tender lymph nodes , throat
inflammation , rash , head ache , sores of mouth.
ACQUIRED IMMUNO DEFICIENCY SYNDROME (AIDS)
5. TRANSMISSION
Unprotected sexual intercourse
Contaminated blood transfusions
Hypodermic needles
From 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).
6. 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.
SMALLPOX
7. A viral disease that causes acute inflammation of brain in
humans and warm-blooded animals.
Caused by rabies virus
The virus travels to the brain following peripheral
nerves.
The disease can only be diagnosed after the start of
symptoms.
SYMPTOMS
Violent movements Of Uncontrolled excitement
Fear of water
Inability to move body parts
Confusion
Loss of consciousness
RABIES
8. 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
Initial symptoms include fever, cough, runny nose and red
eyes.
After 2-3 days small white spots may form inside the
mouth known as Koplik’s spots.
Red flat rashes starts on the face and then spreads to rest of
the body.
Complications include diarrhea, blindness, inflammation of
the brain and pneumonia.
MEASLES
9. 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.
SYMPTOMS
Symptoms include fever, sore throat, watery eyes, body aches,
shortness of breath, headache, weight loss, sneezing, abdominal
pain, lack of appetite and fatigue.
The most common cause of death is respiratory failure.
Other causes of death are pneumonia high fever, dehydration,
electrolyte imbalance and kidney failure.
SWINE FLU
10. 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
SEVERE ACUTE RESPIRATORY SYNDROME
(SARS)
12. Distribution
Apple mosaic virus is one of the oldest known and most
widespread apple viruses. Occur in Bangladesh, Japan, Turkey,
Africa, North and South America and many European countries.
Host Range
65 woody and herbaceous species in 19 families Apple mosaic
Virus (Chestnut mosaic)
Symptoms
• Infected trees develop pale to bright
cream spots, bandings or patterns on leaves.
These spots may become necrotic after
exposure to summer sun and heat.
• Premature defoliation may occur when infection is severe.
• Except in severe cases, infected trees can still produce a crop,
with yield reductions from no reduction to 50%.
Apple mosaic virus
13. Distribution This disease has been known in New Zealand in
1935.
Host Range: Malus pumila, Chenopodium quinoa (Seed)
Symptoms :
• Small yellow spots, sometimes chlorotic rings on the leaves
• Darker green spots or irregular rings on the fruits
• The skin around the lesions light green
or yellow color
• In ripening fruit, the surface of the spots
become rough and rusty.
• No internal fruit symptoms.
• Flavor and storage properties of the
fruits are not affected.
• The spots decrease their marketability
Apple Ring spot Virus
14. Distribution : Widely distributed and best known of virus disease
in India, North and South America and many Pacific and Atlantic
islands.
Host range : Its host range is very wide. Sugarcane, Maize,
Sorghum, elephant grass etc. Mosaic of Sugarcane
Symptoms : First symptom appear about 6 weeks after planting
• Primary and critical symptom is appearance
of pale patches
or blotches in green tissue of leaves
• Patches are oval or elongated lying
parallel to midrib
• Tillers become erect, stiff and crinkled
• Mottling of stem also occur lead to death
of cells
Mosaic Of Sugarcane
15. Distribution
This disease has been known in Spain, New York, America, Eastern
Washington and Hood River Oregon.
Host Range
Malus pumila and Cherry
Symptoms
• This may cause cell death at the graft union
• The resulting symptoms are those of decline, collapse, or tree
breakage.
• Fruits are smaller, flatter, and show a tendency for the calyx end to
be open. Management
•Plant virus-indexed trees.
•If replanting in virus-infected areas of the orchard, use both
rootstocks and scions that are tolerant of the virus.
Apple flat virus
16. Distribution
CTV is one of the well known and most widespread citrus
virus. Occur in Spain, France, Japan, Florida, Australia and
US
Host Range
CTV infects several species of the plant genus, Citrus,
orange ,sweet orange, grapefruit, lime and Seville.
Symptoms
• CTV symptoms are associated with viral disruption of
phloem and its function.
• There are three distinct syndromes of CTV infection:
quick decline, stem pitting, and seedling yellows.
• Affects the cambium layer below the bud union and
prevents the normal development of cambium cells
• In severe case, leaving fruit shriveled on the tree and
leaves brown and dehydrated.
Citrus Tristeza Virus
17. Distribution
Occur in India, Congo, Kerala State, Irian Jaya, Indonesia,
Host Range
BBTV infects several species of the plant genus, Citrus, orange
,sweet orange,
grapefruit, lime and Seville.
Symptoms
• Symptoms appear in the second
• leaf to emerge after inoculation
• Few dark-green streaks or dots on
• the minor veins on the lower portion of the lamina.
•The leaf display whitish streaks along the secondary veins.
•These streaks become dark green.
• Leaves become smaller, both in length and in width of the lamina
• Abnormal shape of fruit produced.
Banana Bunchy Top
18. Distribution
reported in India, Canada, Russia, South Africa and all over the
world. • it causes 16 to 64% losses in tuber yield
Host range
Potato and also attack on tomato.
Symptoms
The leaflets of infected plant roll up along margin
• In infected seed tubers, Rolling of leaves starts in the lower
leaves and progresses upward
• Rolled leaflets become stiff, rigid, thick and leathery.
• Internodes are shorts resulting in dwarfing or stunting of entire
plant,
• Necrosis occur in primary phloem
Leaf roll of Potato
19. Distribution
This virus is spread worldwide, particularly in Europe
Host range
Its host range is very wide. • Bean, melon, cucumber, tulip
Symptoms
• Brown necrotic spots appear near the veins, they may be
coalescing.
• Occasionally young seedlings die.
• dark sunken lesions formed on
• On mature plants, the symptoms are mainly located on the
lower leaves.
Tobacco Necrosis Virus
