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Infectious Diseases: Causes, Symptoms and Treatment

April 14, 2018

Viral infection

Shalby Team

General Medicine, Infectious Diseases


Infectious diseases are the health disorders that are caused by infection causing organisms that use human body for surviving, reproducing and colonizing. These organisms are known as pathogens. The commonly known pathogens include virus, bacteria, fungi or parasites.

Some of the infectious diseases are very mild and cause no harm. However, certain infectious diseases are very severe and can even be life-threatening.

These diseases can even be transmitted from one person to other through various means. Some get transferred via insect or animal bite while some are usually acquired when you ingest contaminated food or water. As there are various pathogens that cause infectious diseases, the signs and symptoms also vary based on the pathogen type that has infected you.

Let us here understand the symptoms of infectious diseases, what all types of pathogens cause infectious diseases and how these diseases can be prevented and treated.

Symptoms of Infectious Diseases

As stated, symptoms of any infection will vary based on the organism type that’s responsible for the infection; the site of infection will also have an impact on the symptoms, an infected person will show.

Among the different pathogen types, viruses are known to target precise cells. These mostly include your genitals or the upper respiratory tract. For instance, rabies virus will affect your nervous system, warts caused by viruses target your skin, virus that causes flu will make you suffer from runny nose, upset stomach or pain in muscles.

If you have encountered a bacterial infection, then you are likely to suffer from swelling, fever, redness and pain at the place of infection.

Rashes on the skin are often the sign of fungal infection.

Diseases caused by prions will cause symptoms as memory loss, brain damage and cognitive difficulties. Sometimes, prions can even trigger plaque buildup in your brain, which can lead to the brain gradually losing its functionality.

Infection Causing Pathogens

The most commonly known pathogens that cause infections include bacteria, fungi, viruses, protozoa, prions, and parasites. These pathogens differ from one another in terms of shape, size, genetic content and function.

As compared to bacteria, viruses tend to be much smaller. This helps them to enter the host body with ease and allows them to overpower the cells. Bacteria on the other hand can survive without any host.

If you have encountered an infectious disease, the treatment type will depend on the pathogen type that has caused the disease.

Let us have a look at the infections as caused by the different pathogens:

Viral Infections

Infectious Diseases: Viral Infection Causes  

There are over millions of viruses in existence but only 5,000 virus types have been classified. They are small particles with a genetic code and a coating of fat and protein. Viruses can’t reproduce themselves; they need a host body for this purpose.

As viruses enter the host body, they release their genetic material into the host body’s cells and take control of the cells internal machinery. These viruses multiply by making the cells to replicate. Eventually, the healthy cells are destroyed by the viruses while the latter continues to grow.

Certain viruses don’t destroy the host cell, they rather change the cell functioning. For instance, Human Papillomavirus (HPV) or Epstein - Barr virus (EBV) forces the cells to multiply in an unchecked manner that leads to cancer in most cases.

Viruses can even target specific age groups as infants or young children. Sometimes the virus can stay dormant for a certain period before it multiplies again. During the time the virus is dormant, the infected person may seem to have recovered but the condition recurs as soon as the viruses become active.

For example, viruses that cause cold and chicken pox remain inactive post the initial infection. The virus will remain in an inactive state but as soon as it gets triggered by conditions like stress or sunlight, the infection symptoms start to resurface.

Some of the commonly occurring viral infections:

  • common cold, it is caused by the rhinovirus, adenovirus and coronavirus
  • warts and skin infections, caused by the human papillomaviruses (HPV) and herpes by simplex virus (HSV)
  • encephalitis and meningitis, caused by enteroviruses and the herpes viruses
  • gastroenteritis, caused by the novavirus

Other known viral infections:

    • Zika Virus
    • HIV
    • Hepatitis C
    • Influenza
    • Dengue Fever
  • H1N1 Swine Flu
  • Polio
  • Ebola
  • Middle East Respiratory Syndrome (MERS-Cov)

To treat conditions infected by virus, antiviral medications are mostly preferred. Antiviral mediations help by either preventing the virus from multiplying or by boosting the immune system of the host body. Antibiotics are not favoured in the case of viral infections because they are not effective in destroying the virus. Antibiotics pose a risk of increasing antibiotic resistance.

Bacterial Infections

Bacterial Infections  

Compared to viruses, bacteria happen to be quite complex, single-celled microorganisms. They contain a stiff wall, with a thin and rubbery membrane that surrounds the fluid present in the cell.

Unlike viruses, bacteria can survive on their own, even in the extreme environmental conditions like severe cold or heat. Most of the bacteria are harmless and help human body in different ways like destroying the microbes that cause diseases, fighting the cancer causing cells and giving essential nutrients. Only a small percentage of bacteria actually cause diseases in human beings. Bacteria majorly take three shapes, which include:

Spherical: Bacteria that are spherical in shape can be treated easily and are commonly known by the name, cocci.

Rod-shaped: Known as bacilli, this bacteria type is known to cause disease related to the intestine, urinary tract and meningitis.

Spiral: They are coiled and are known as spirilla. And when the coil is quite tight, they are called spirochetes.

Some of the diseases caused by bacteria include:

  • Diphtheria
  • Dysentery
  • Cholera
  • Bubonic plague
  • Pneumonia
  • Typhoid
  • Typhus
  • Tuberculosis

Some of the commonly known bacterial infections include:

  • bacterial meningitis
  • pneumonia
  • skin infections
  • tuberculosis
  • otitis media
  • upper respiratory tract infection
  • food poisoning
  • eye infections
  • gastritis
  • sinusitis
  • urinary tract infections
  • sexually transmitted diseases

In most cases, bacterial infections are treated with antibiotics, however; some bacteria become defiant and can withstand the treatment.

Fungal Infection

Human body has a store house of good bacteria that help in maintaining the balance of microorganisms in your mouth, vagina, intestines and other body parts. When a certain amount of good bacteria get destroyed then it paves way for the fungus to develop and cause different health issues.

Fungus is a multi-cellular parasite that decomposes and then absorbs organic matter with the help of an enzyme. Fungi reproduce by single-celled spores which spread in the host body. Fungi’s structure is usually long and cylindrical and has small filaments that branch from the main body. This structure is called the hypha. There are around 51 million fungus species.

Generally fungal infections occur in skin’s upper layers but some fungus can even pass on to the deeper skin layers. When the fungal spores are inhaled they can cause systemic fungal infections like thrush, or candidiasis. Systemic diseases are known to hamper the functioning of entire body.

Some people stand at a higher risk of developing fungal infections, which include people who have been using strong antibiotics for a long time, weak immune system due to diabetes, chemotherapy or HIV, undergone a transplant and take medications for preventing the body from rejecting the new transplanted organ

Commonly known fungal infections include:

  • valley fever, or coccidioidomycosis,
  • ringworm
  • some eye infections
  • athlete's foot
  • rash on skin


A prion is defined as a small proteinaceous agent that causes infectious disease. It has no genetic material and is neither categorized as bacterial, fungal nor viral. Though it is usually harmless, things can become troublesome if prions take an abnormal shape.

Unlike virus, prios don’t replicate or feed on the host body but they can trigger abnormal behavior in host body's cells and proteins.

Prions are known for affecting the brain and various other parts of the nervous system. They can lead to degenerative brain diseases, like the mad cow disease, fatal familial insomnia, and a type of hereditary dementia called Gertsmann-Straeussler-Scheinker disease.

The diseases caused by prions are rare, but they tend to progress rapidly, and prove fatal.

Other infections

Other than the above-mentioned infection types, there are other pathogens also that can infect the body.

Among such is the protozoa, which is a single-celled organism and has a nucleus. It is known to cause protozoan infection. A protozoa usually exhibits features like that of animals like mobility and can easily survive outside human body. Protozoa commonly gets transferred when in contact with feces.

When in the human body, protozoa can lead to infections like amebic dysentery.

Other infection causing pathogens are the helminths which are larger and multicellular organisms for example, flatworms and roundworms.

Then there are ectoparasites like ticks, mites, lice, and fleas that cause infection by either attaching or burrowing into the host skin.

How Does Infectious Diseases Spread?

In general, infectious diseases spread from one person to other either by direct or indirect contact. Some of the infectious diseases caused by different bacteria, viruses, fungi and parasites include measles, malaria and illness of the respiratory organ.

Let us here understand how the transmission of infectious disease happens.

Direct Contact

Mostly, infectious diseases get spread via direct contact. Some of the common types include:

1. Person-to-person

Transmission of infectious diseases occurs from one person to other when the infected person happens to touch or exchange his or her body fluids with someone who is not infected. Most sexually transmitted diseases are spread in this manner. Pregnant women can also transfer infectious diseases to the unborn child through the placenta.

2. Droplet spread

Another type through which infectious diseases get spread is the droplet spray when an infected person coughs or sneezes. Infection can even be spread through droplets while speaking. However, given the fact that droplets usually fall on the ground , over a few feet, the droplet spread happens only in close proximity.

Indirect Contact

In case of indirect contact, infectious diseases get spread via air and other mechanisms. Some of which include:

1. Transmission through air

Certain infectious agents travel long distances and stay suspended in the air for a longer period of time and can be transferred when the infected air is inhaled.

2. Contaminated objects

Some infectious disease causing organisms live on the objects for a short time. When you touch an object like a doorknob, right after it is touched by an infected person, you stand at a higher risk of catching the infection. Transmission of such organisms can even occur when you touch your eyes, nose or mouth after touching a contaminated object. Germs can even be spread via contaminated blood products as well as medical supplies.

3. Animal-to-person contact

Certain infectious diseases get transmitted from an animal to a person. This usually happens when you get bitten or scratched by an infected animal. Handling animal waste can even make you prone to catching the infection. For example, Toxoplasma gondii parasite is said to be found in cat feces. People with a weak immune system must ensure to take proper precaution when handling animal waste or dealing with animals.

4. Food and drinking water

Food and drinking water also serve as the ideal choice for the transmission of infectious diseases. E. coli is usually transmitted via clumsily handled food product or undercooked meat.

5. Animal reservoirs

Diseases that are usually transmitted from animal-to-animal can also be transferred to humans. Zoonosis is the term used for the diseases transferred from animals to people. Some of the Zoonotic diseases include:

  • Anthrax, transferred from sheep
  • Rabies, transferred from rodents and other mammals
  • West Nile virus, transferred from birds
  • Plague, transferred from rodents

6. Insect Bites

Insect bites, mosquitoes and ticks

Certain zoonotic infectious agents get transmitted through insects, particularly the ones that suck blood such as the fleas, mosquitoes and ticks. The insects get infected as they feed on the infected hosts like humans, animals and birds. The disease then further gets transmitted when the infected insect bites a new host. Diseases like malaria, Lyme disease and West Nile virus are spread in this manner.

How Infectious Diseases Can Be Prevented?

Infectious diseases can subject you to various health problems, many of which can even be fatal. This is why, it is very important that you take proper care so as to prevent the infectious disease.

It can be prevented easily if you take good care of your personal hygiene and be mindful about certain things. Some of the ways that can help prevent infectious diseases include:

Washing hands frequently

Washing hands frequently

Your hands can serve as the perfect hideout for different bacteria types. And as you touch your face, mouth eyes or nose, you tend to transmit those disease causing bacteria. Touching contaminated objects can also make your hands at risk of infection from parasites, viruses and other microorganisms. To ensure that you stay safe from any microbe attack, you should make it a habit to wash your hands frequently with soap and water. If at times you can’t reach out to clean water and soap, make sure to use a hand sanitizer.

Cough and sneeze by covering your mouth

Droplets that come when you cough and sneeze are the primary source of spreading infection. Even if you are not sick, you should make it a point to cover your mouth when sneezing or coughing. And never use your bare hands, always use a handkerchief, or cover the mouth with your arms, sleeve or the crook of the elbow.

Maintain hygiene when cooking food

Many of the infectious diseases are spread through the food you eat. To prevent that you should make it a point to follow strict hygiene when cooking food. Keep the cooking area clean, wash all fruits and vegetables thoroughly and don’t keep food stocked in the refrigerator for longer duration.

Get vaccinated

Get vaccinated  

Human immune system is designed in a way that it retains the memory of past infections. If you encounter an infection, which had occurred in the past also, your body will automatically increase the production of white blood cells and antibodies for preventing the infection from recurring. When you get vaccinated for a disease, it tricks the body into believing that it has been infected by a disease and the immune system starts forming the defend mechanism.

Practice safe sex

There are various sexually transmitted diseases that can have an adverse effect on your overall health. To prevent such diseases, you should make it a point to practice safe sex.

Don’t share personal items

Sharing is good but not at the expense of your health, or for that matter the health of people around you. It is advisable that to prevent infectious diseases, you should abstain from sharing your personal items like razors, toothbrushes, towels, nail clippers and handkerchiefs.

Diagnosing Infectious Diseases

Laboratory Tests

Laboratory tests, blood tests, urine test  

Most of the infectious diseases tend to have common signs and symptoms. To make sure which infectious disease you are suffering from, sample of body fluids are needed. Some of the tests are:

Blood tests: A sample of your blood will be taken from the arm to check the precise type and cause of the infectious disease.

Urine tests: You will be asked to collect your urine sample in a container, which is then tested for the presence of infection.

Throat swabs: A sterile swab is used to take sample from the throat, or other moist areas of the body.

Stool sample: For checking the presence of parasites and other disease causing organisms, your doctor will even instruct you to collect your stool sample.

Spinal tap (lumbar puncture): In this process, a sample of cerebrospinal fluid is taken via a needle that’s inserted between the bones of lower spine.

Imaging Scans

Different imaging procedures like X-rays, magnetic resonance imaging (MRI) and computerized tomography helps in precisely diagnosing the cause of your disease and ruling out the possibility of any other disease that has been causing the symptoms.


In some cases, if the result needs more precision, your doctor will recommend a biopsy. In this process, a small sample of tissue will be taken from an internal organ.

Treating Infectious Diseases

Based on the diagnosis, which helps in knowing the microorganism type causing the disease, your doctor will decide the treatment plan.

Some of the common treatment methods used in treating infectious diseases include:

Antibiotics: Antibiotics are normally prescribed in the cases of bacterial infections as these antibiotics have no effect on the diseases as caused by viruses. When antibiotics are overused, bacteria form a resistance to them and in such cases, treating the bacterial infection becomes very difficult.


Antivirals: There are certain drugs that can treat some of the viral infections but not all. Such viruses include:

  • Hepatitis B
  • Hepatitis C
  • Herpes
  • Influenza

Antifungals: To cure the fungal infections, topical antifungal medications are highly recommended. These medications can be used in treating the skin and nail infections as caused by fungi. Some of the fungal infections, like the ones that affect your lungs or the mucous membranes, can also be treated with oral antifungal. If the fungal infection is very severe, or the immune system is very weak, then in such cases doctors usually recommend intravenous antifungal medications.

Anti-parasitics: Diseases like malaria are often caused by tiny parasites. Though there exist medications to treat diseases caused by parasites, certain parasites have become resistant to the drugs.


Infectious diseases can be controlled and prevented easily if the basic hygiene measures are taken care of. Moreover, timely diagnosis of infectious diseases is very important for timely treatment which will offer effective results.

At Shalby Hospitals, we have a team of highly skilled and proficient doctors who specialize in treating a range of infectious disease using the latest treatment approach. Our team of experts not only help with proper diagnosis but even assist in planning the right treatment program that can cure the problem and help prevent its recurrence.


Shalby Team

Shalby Hospitals (Shalby Limited) is recognised as a multispecialty hospital chain in the Indian healthcare industry. Dr Vikram I. Shah established the first hospital in 1994 in Ahmedabad, Gujarat. Dr. Shah has been felicitated by Ethicon India for the development…


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