Nonlinear Dynamics And Simulation of Infectious Diseases In Humans

An infectious disease is a disease due to a specific infectious agent or its toxic prod-

ucts that arise through the transmission of that agent or its products from an infected person

animal or reservoir to a susceptible host either directly or indirectly through an intermediate

plant or animal host vector or the inanimate environment. Various microbes or pathogens

cause infectious diseases. Most of them are generally microor- ganisms and few of

them are observable by naked eyes. The most commonly known pathogens are different types

of viruses and bacteria. Fungi and Proto: toa are also known

as pathogens that are responsible for many diseases. Diseases caused by these pathogens are termed as "infectious" as these pathogens can be transmitted from one infected per-

son to another non-infected person. The most common and well-known example of such diseases is

intluen'.a or tlu caused by some kinds of viruses. Pathogens can be transmit- ted either

directly or indirectly. Direct transmission involves the spread of pathogens by direct

body-to-body contact, such as mother to child as exemplified with HIV, Zika, and syphilis, touching

(MRSA), kissing (herpes simplex virus), and sexual contact (hu- man papillomavirus or HPV).

Indirect contact transmission occurs when pathogens are transferred between individuals via a

contaminated intermediate person, object, or en- vironmental surface 53J. Many infectious

diseases (for example, HIV, mumps, measles, rubella, smallpox, malaria) are still prevalent at

local or global scales and threaten public health. An outbreak of an infectious disease affecting

a disproportionately large number of individuals in a population, community, or region within a

short period is known as an epidemic.

Infectious diseases can spread in various ways, and pathogens cause infections by dif-

ferent modes of transmission. Contact is one of the most critical and frequent methods of

transmission of infectious diseases. It can be either direct or indirect. Direct contact involves

the physical transfer of microorganisms to a susceptible host from an infected or coloni'.ed

person. Direct contact includes a large droplet spread of infectious agents. Other direct contact

transmission examples are kissing, shaking hands or other skin con- tacts, sexual contact, and soil

contact. Indirect contact occurs when organisms from an infected host or other reservoir are

transmitted to a susceptible host via a contaminated intermediate object. Indirect contact

transmission may be airborne, vector-borne, or vehicle-borne. Many diseases, e.g.,

infiuen'.a, SARS, are airborne and can be transmitted through the air. The airborne infection

spreads from an infected person to an uninfected person through snee'.ing, cough, and even

laughter. The microbes that are discharged from an infected person may remain on the dust particles or any other medium.