Infections a common term used for variety of group of symptoms or signs shown by a person. It is a very common term used by everyone in their life at some point of time. The current scenario of pandemic has given more popularity to the word 'INFECTION'. The whole world is currently fighting a pandemic which has not only caused health damage but also has devastated economies. hence, it is very important in this period to understand what exactly it means by infection and what could be the potential causes and effective treatments. After all the covid19 pandemic is nothing but infection caused by pathogens.

According to WHO definition of infectious diseases

Infectious diseases are caused by pathogenic microorganisms, such as bacteria, viruses, parasites or fungi; the diseases can be spread, directly or indirectly, from one person to another. Zoonotic diseases are infectious diseases of animals that can cause disease when transmitted to humans.

But, we are more interested on knowing about infections per say ;

Infection to describe is invasion of microorganisms in the body of the person and grow and multiply their causing release of certain toxins and agents which cause damage to healthy tissues and cells and ultimately affecting the health of the individual.

There could be several ways by which infections can spread and cause more damage to the individual.

  • Through direct contact with the infected person

  • Contaminated food

  • Insect bite

But there are several different ways by which the infection can be transmitted from one person to other. Not all infections spread the same way and can cause the same damage.

Depending upon the type in infection the signs and symptoms may vary and treatment too.

Infections are acquired by various microorganisms which infect the individual by various methods. Here is the list of microorganisms which can cause infections.

  • Bacteria

  • Virus

  • Fungi

  • Parasites

These are the microorganisms which are responsible for causing infections; the name given to the infections caused by these organisms are as follows;

  • Bacterial infection

  • Viral Infection

  • Fungal Infections

  • Parasite


There is a general chain of events that applies to infections. The chain of events involves several steps – which include the infectious agent, reservoir, entering a susceptible host, exit and transmission to new hosts. Each of the links must be present in a chronological order for an infection to develop.


Infection begins when an organism successfully enters the body, grows and multiplies. This is referred to as colonization. Most humans are not easily infected. Those with compromised or weakened immune systems have an increased susceptibility to chronic or persistent infections.

Individuals who have a suppressed immune system are particularly susceptible to opportunistic infections. Entrance of microorganisms in the human body generally occurs through the mucosa in orifices like the oral cavity, nose, eyes, genitalia, anus, or the microbe can enter through open wounds.

While a few organisms can grow at the initial site of entry, many migrate and cause systemic infection in different organs. Some pathogens grow within the host cells (intracellular) whereas others grow freely in bodily fluids.


Disease can be caused when host's protective mechanism is affected and the microorganism has caused damage to the host cells. The damage is usually caused by the release of the toxic enzymes by the microbes. Not all infectious agents cause infections in all hosts. Some of the agents are really virulent and harmful. Persistent infections occur as a result of body unable to release the initial organism from the body and hence the agent tries to attack the host cells again and again. Persistent infections cause deaths all over the world every year.


Transmission occurs when the infected organism passes from one reservoir to other and there several ways of transmission of the infection from one host to another. The potential routes of transmission are as follows;

  • Droplet contact, also known as the respiratory route, and the resultant infection can be termed airborne disease. If an infected person coughs or sneezes on another person the microorganisms, suspended in warm, moist droplets, may enter the body through the nose, mouth or eye surfaces.

  • Fecal-oral transmission, wherein foodstuffs or water become contaminated (by people not washing their hands before preparing food, or untreated sewage being released into a drinking water supply) and the people who eat and drink them become infected.

  • Sexual transmission, with the resulting disease being called sexually transmitted disease

  • Oral transmission, Diseases that are transmitted primarily by oral means may be caught through direct oral contact such as kissing, or by indirect contact such as by sharing a drinking glass or a cigarette.

  • Transmission by direct contact, Some diseases that are transmissible by direct contact include athlete's foot, impetigo and warts

  • Vehicle transmission, transmission by an inanimate reservoir (food, water, soil)

Vertical transmission, directly from the mother to an embryo, fetus or baby during pregnancy or childbirth. It can occur as a result of a pre-existing infection or one acquired during pregnancy.

  • Iatrogenic transmission, due to medical procedures such as injection or transplantation of infected material.

  • Vector-borne transmission, transmitted by a vector, which is an organism that does not cause disease itself but that transmits infection by conveying pathogens from one host to another.

To understand the infections lets go on to the individual infection types and understand their scope , spread and treatments.

understand infection

Bacterial Infections

Bacteria are microscopic single cell, organisms that live on almost everything. Bacteria's are not always harmful, some of the bacteria's are essential for the body, especially for the bacteria's that are present in the human gastrointestinal system which are essential for the gastrointestinal system.

However, sometimes bacteria can enter our body and cause infections.

  • Strep throat

  • Gonorrhea

  • Chlyamdia

  • Tuberculosis

  • Whooping Cough

  • Tetanus

  • Bacterial Meningitis

  • Syphilis

  • Pneumonia

  • Cellulitis

  • Urinary tract infection

These are the commonly noted conditions associated with bacterial infection that are found .


Direct contact with the bacteria occurs when a person comes in contact with the infected food, beverages, animal carrying the bacteria, bitten by the insect or by inhalation of the bacteria emitted by cough or sneeze of an infected person.

Signs and Symptoms

Symptoms of bacterial infections vary depending upon the area that has been affected by the bacteria, however, there are some generalized signs and symptoms noted;

  • Fever

  • Pain in the affected region

  • Redness or swelling , which may also be noted in lymph nodes

  • Cough

  • Fatigue or feeling tired

  • Abdominal Pain

  • Burning sensation while urinating.

  • Shortness of breath

  • Chills or sweating.

  • Headache

As mentioned earlier , these are generalized symptoms which may vary upon the type of bacteria and the area where it has affected the body.

Bacterial infection may cause acute or chronic conditions and can show , mild , moderate or severe symptoms



Antibiotics is usually the first line of treatment preferred in bacterial infections.

In Greek Anti means oppose and bio means life, so specifically , antibiotics are the medicines which is anti microbial substance against bacteria, which help in treatment of bacterial infections. They treat infections by killing or by inhibiting the action of bacteria.

Viral Infection

Virus is a tiny microorganism smaller than bacteria. Virus is composed of genetic material which is surrounded by protein materials. Virus can multiply only when they are present in the host cell.

Viral infection is caused by proliferation of the virus within the body of the person. Viruses also have property of copying themselves and can kill the host cells, causing increase in number of new virus. The common examples of viral infections are as follows :

  • Influenza ( Flu)

  • Common Cold

  • Measles

  • Rubella

  • Polio

  • Human Immunodeficiency Virus ( HIV)

  • Human papillomavirus ( HPV)

  • Rabies

  • Ebola

  • Corona virus ( Covid 19)

  • Viral Meningitis.


Viruses can spread through saliva, touch or even by air. Some viruses can be transmitted through contaminated needles, sexual contact or even mosquito bites of mosquitoes carrying vector or ticks of that virus.

Contaminated food and water can also be one route of spread of virus in few cases .Some viruses may stay in your body till your lifetime, they can lie dormant in your body and reactivate examples being HPV OR HIV. Precautions are very important to avoid the spread of viral infections.

Signs and Symptoms

The viral infections may lead to symptoms as per the system that it has affected but the generalized signs and symptoms of viral infections are as follows;

  • Fever ( could be low grade or high grade depending upon the type and severity of infection)

  • Cough and Cold

  • Generalized feeling of unwell or weakness

  • Body aches or joint pain

  • Skin rashes

  • Redness

  • Congestion and runny nose

  • Diarrhea or bowel changes

  • Breathlessness


Management of viral infection includes treatment of symptoms mainly antibiotic treatment as mentioned earlier is not effective in treating viral infection. Immunity is very vital in clearing the viral infections from the body.

Antiviral medicines could be prescribed. Antiviral drugs are the medicines used in treating viral infections, most antivirals target specific viruses, while broad spectrum viruses are effective against wide range of viruses. These medications act by inhibiting the action or growth of the virus .

Symptomatic treatment may include treating the specific symptoms . Some of the viruses have preventive vaccines to avoid the viral infections.

Fungal Infections

Fungi can live in air, soil, water. There are different types of fungi that are present , but harmful fungi can invade and pose damage to human body. Fungi are diverse group of organisms that include things like yeast, molds. The commonly seen fungal infections are as follows:

  • Athlete's foot

  • Skin fungal infections

  • Aspergillosis

  • Vaginal yeast infections

  • Fungal meningitis

  • Ringworm


Fungal infections can spread from one part of body to other. They can pass from one person to other by skin to skin contact or by using contaminated clothes of the infected person. The infection can also spread by skin to skin contact of infected person to non infected person.

Signs and Symptoms

The fungal infections may show signs and symptoms in the area where the fungus as invaded. So, there could be local signs and symptoms. General signs and symptoms of fungal infection are as follows;

  • Redness or blisters

  • Skin itching or peeling

  • Pain around the infected area

  • Swelling and redness

  • Increase in local temperature or general body temperature.

  • Discharge from the infected site.

  • Cracking of skin.

  • Weakness

These are the generalized signs and symptoms of the fungal infections as mentioned earlier site of infection can change or the infection may spread . The symptoms may vary according to level of infection.


Anti fungal medications are prescribed in the cases of fungal infections. Anti fungal medications can be in the form of topical creams, lotions or even oral medications.

In few cases intravenous drugs could also be given to the infected patient. There are various classes of anti fungal medicines and their mechanism of action is inhibiting the growth of fungus and reducing the infection.

As always said, Prevention is better than cure , avoiding contact is best way to prevent the spread of fungal infection.

Parasitic Infection

Parasites are the organisms that live on the other organisms called as 'Host'. Parasites can be microscopic or large enough to be seen by naked eyes. They survive by feeding on the host. There are 3 types of parasites that can infect the human body;

  • Protozoa

  • Helminth

  • Ectoparasites

Protozoa are small one celled organisms. Helminth are worm like organisms and ectoparasites are the large, visible organisms like fleas, lice, ticks.

The commonly known parasitic infections are as follows;

  • Malaria

  • Toxoplasmosis

  • Trichomoniasis

  • Tapeworm infection

  • Head lice

  • Scabies.


Parasitic infection can spread by many ways; It can spread from contaminated food, soil, water and blood. Some of the infections can spread by sexual contact.

While some infections are caused by insects that act as carrier. Few parasites can invade human body by coming in contact with infected animal or animal carrying the parasite which then invades the human body.

However there are certain risk factors for spread of parasitic infections , they are as follows;

  • Immunity- People having compromised immunity may be more prone to get infected.

  • Climate- Tropical or sub tropical country people are at risk of developing the infection due the climatic conditions.

  • Environmental Factors - Working environment or living conditions can make a person at risk, like working in mud, unclean water or living conditions.

Signs and Symptoms

Signs and symptoms depend upon the area and the type of parasite that has invaded the human body. The general signs and symptoms of parasitic infections are as follows;

1) Swelling at the site of infection

2) Redness or pain

3) Low grade fever

4) Fatigue

5) Headache

6) Nausea, vomiting, Diarrhea.


Anti- parasitic medicines are usually prescribed for the parasitic infections. Many a times a mild infection can go by itself without need for taking medicines.

The anti-parasitic medicines are prescribed as per the severity of infections and also according to the type of parasite that has invaded the body.

Along with these medicines, sometimes, even symptomatic treatment may also be given to reduce the severity of symptoms. The ant- parasitic medications act by reducing the number of parasite and their effect or eliminating the parasites completely from the body.

Diagnosis of the infection

Diagnosis of the infection involves identifying the agent that has caused the infection in the human body.

General medical history and assessment of the individual would give an indication of presence of the infectious agent and severity of its presence.

Detail diagnosis can be done by assessing the culture taken from the human body and testing it at the cellular level to understand the presence of the agents.

Symptomatic Diagnosis

It is usually done by assessment of history and signs and symptoms shown by the person based on the specific signs and symptoms diagnosis can be made and presence of infection can be confirmed.

Microscopic Testing

The signs and symptoms may give an idea of infection , but confirmation may sometimes require testing the microbial culture from the host body. The microbial culture is collected from the body fluids or infected site and then assessed and the presence of infectious agents is confirmed. This test would also help us in getting information of type of agent and the severity of multiplication of the that agent.

Biochemical Tests

These tests are performed to identify the structure of the microorganism at the cellular level. these tests tell us about the structure of the microorganism like, whether the constituent of the cells within the microorganism is protein, carbohydrate etc. This test is essential to understand the structure of the microorganism and the way it would be progressed in the human body.

PCR Based Tests :

This test are usually considered the gold standard which gives a confirmation of the presence of microbial activity and helps in confirming the diagnosis. PCR stands for polymerase chain reaction . these are the blood tests that give an confirmation of the activity of infectious agent.


Techniques like hand washing, wearing gowns, and wearing face masks can help prevent infections from being passed from one person to another.

Aseptic method was introduced in medicine and surgery in the late 19th century and greatly reduced the incidence of infections caused by surgery. Frequent washing of hands remains the most important defense against the spread of unwanted organisms.

There are other forms of prevention such as avoiding the use of illicit drugs, using a condom, wearing gloves, and having a healthy lifestyle with a balanced diet and regular exercise.

Cooking foods well and avoiding foods that have been left outside for a long time is also important.

Antimicrobial substances used to prevent transmission of infections include:

  • antiseptics, which are applied to living tissue/skin

  • disinfectants, which destroy microorganisms found on non-living objects.

One of the ways to prevent or slow down the transmission of infectious diseases is to recognize the different characteristics of various diseases.

Some critical disease characteristics that should be evaluated include severity of virus, distance traveled by victims, and level of contagiousness. The human strains of Ebola virus, for example, incapacitate their victims extremely quickly and kill them soon after.

As a result, the victims of this disease do not have the opportunity to travel very far from the initial infection zone.

Also, this virus must spread through skin lesions or permeable membranes such as the eye. Thus, the initial stage of Ebola is not very contagious since its victims experience only internal hemorrhaging.

As a result of the above features, the spread of Ebola is very rapid and usually stays within a relatively confined geographical area. In contrast, the HIV kills its victims very slowly by attacking their immune system.

As a result, many of its victims transmit the virus to other individuals before even realizing that they are carrying the disease. Also, the relatively low virulence allows its victims to travel long distances, increasing the likelihood of the epidemic.

Another effective way to decrease the transmission, In epidemics, there are often extensive interactions within hubs or groups of infected individuals and other interactions within discrete hubs of susceptible individuals.

Despite the low interaction between discrete hubs, the disease can jump to and spread in a susceptible hub via a single or few interactions with an infected hub.

Thus, infection rates in small-world networks can be reduced somewhat if interactions between individuals within infected hubs are eliminated.

However, infection rates can be drastically reduced if the main focus is on the prevention of transmission jumps between hubs.

The use of needle exchange programs in areas with a high density of drug users with HIV is an example of the successful implementation of this treatment method.

Another example is the use of ring culling or vaccination of potentially susceptible livestock in adjacent farms to prevent the spread of the foot and mouth virus in 2001.

A general method to prevent transmission of vector-borne pathogens is pest control.

In cases where infection is merely suspected, individuals may be quarantined until the incubation period has passed and the disease manifests itself or the person remains healthy.

Groups may undergo quarantine, or in the case of community spread may be imposed to prevent infection from spreading beyond the community. Public health authorities may implement other forms of social distancing , such as school closings, to control an epidemic.


Immunity plays very important role in understanding the spread and also preventing the transmission of disease from one individual to other.

Improving immune system could one of the best way to prevent the transmission of the disease and remain healthy. immunity can be improves by following a healthy diet regime, exercises and remaining stress free.

Vitamin and other vital nutrients also help in maintaining the immunity and help in improving the health and general wellbeing of the individual , which in turn would improve the health and reduce the chances of getting the specific infection.

Boost immunity and remain healthy also avoid infections in the body.

These are the commonly found infections in the body, the conditions mentioned above are examples and there can be variety or combinations present according to type and invasion of the microorganism.

In the current era, Infection is a bigger entity or disease that has cause damage across globe and hence, it is very important to have an overview of the different types and causes of infection and also to understand their spread.


The infections would remain on the earth, as the presence of mankind is eternal so is of microorganism. Hence, it is very important to understand the different types and causes and treatments of these infections. Most of all as said, PREVENTION IS BETTER THAN CURE, taking proper precautions and avoiding the things that would contact or spread disease is very important.

Take all necessary precautions, remain healthy by regular exercise and healthy diet and keep the infections away from your body. And even if you get contracted with the infection, stay calm and visit the doctor and get assessed as early as possible and follow the medical treatment as advised and live healthy.