Question

Why are Infectious Diseases very common?

Answer 1

Hint: Infectious diseases are a type of diseases, which are caused by microorganisms. Microbes move from one person into another in numerous ways. Since the diseases are communicated from person to person, they are also called communicable diseases. Micro-organisms like fungi, parasites, bacteria and viruses are the causal agents for infectious diseases.

Complete answer:
Infectious diseases are caused by pathogenic organisms. Humans, insects and animals are responsible for the transmission of infectious diseases. Infectious agents are ubiquitous. Single celled organisms like bacteria, fungi and multicelled organisms like worms are also known to cause these diseases.
Infectious diseases can be spread via the following modes:
When a new person touches the area, which was already infected, there is transmission of infection from old person to new person and disease is caused. This is air transmission.
When an infected person or infected person’s body fluids like urine, sweat, saliva, blood are touched by a healthy person, the healthy person will get infected. E.g., measles, chickenpox. This is fluid transmission.
When an already infected person coughs or sneezes, the droplets, which contain the pathogens, will spread in the air and infect healthy persons in neighboring areas. This is surface transmission.
AIDS and syphilis are examples for sexual transmission.
They also spread faecal contacts. Lice and mites stick to healthy people's skin and transfer the infection.
Since these diseases spread speedily, easily communicative and affecting in larger numbers, they are very common.

Note:
These are some of the examples of infectious diseases. Worms cause elephantiasis. Virus causes dengue, influenza, AIDS and common cold. Bacteria can cause fever, cholera and typhoid. Trypanosoma causes sleeping sickness. Further, polio, mumps, plague, malaria, meningitis, diphtheria, hepatitis A, hepatitis C, hepatitis B, tuberculosis, yellow fever, anthrax, covid-\[19\] and whooping cough are other infectious diseases.