What is a disease?
A deviation from the normal healthy state of an organism to an unhealthy or abnormal state can be described as a disease.
What is epidemiology of plant disease?
Epidemiology focuses on the occurrence and transmission of diseases within population. The study of outbreak of a disease and its spread is necessary for the control of disease.
Some of the definitions are as follows:
According to William H. Foege (Epidemiologist and Pathologist):
"Epidemiology is the science of understanding the distribution and determinants of disease in populations, aiming to prevent illness and promote health. For pathologists, it bridges the microscopic world of cellular changes with the macroscopic patterns of disease in society.
According to John Snow
Epidemiology provides the framework for understanding the underlying pathological mechanisms behind disease transmission and distribution, using empirical data to inform interventions.
An Epidemic disease can be:
1.Cyclic: When a disease occurs periodically after certain time interval then it is said to be Cyclic. Examples:
Bunchy Top of Banana (Banana Bunchy Top Virus):
Found in specific tropical and subtropical regions, where the virus and its aphid vector are endemic.
Citrus Canker (Xanthomonas axonopodis):
Prevalent in areas with warm and wet climates, like parts of Asia and the Americas.
2.Endemic: When a disease spread to a particular area or state it is said to be pandemic.
Downy Mildew (Peronospora and Plasmopara species):
Affects crops like grapes and leafy vegetables in wet and cool conditions, appearing cyclically.
Apple Scab (Venturia inaequalis)
In temperate climates during spring and summer due to optimal conditions for fungal growth.
3.Pandemic: When a disease occurs and spread in most of continent or all over the world it is called as Pandemic.
Late Blight of Potato (Phytophthora infestans):
A 19th-century pandemic disease that devastated potato crops across Europe.
Wheat Stem Rust (Puccinia graminis sp. tritici):
Threatening global wheat production.
Watch out the complete explanation video:
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