Infectious Diseases: Symptoms, Causes, Risk Factors, Complications, Prevention and Treatment

They are disorders caused by organisms such as bacteria, viruses, fungi, or parasites. Many organisms live in and on our bodies.

Some infectious diseases can be transmitted from person to person. Some are transmitted by insect or animal bites. And others are acquired by eating contaminated food or water or by exposing themselves to organisms in the environment.

Signs and symptoms vary depending on the organism that causes the infection but often include fever and fatigue. Mild conditions can respond to rest and home remedies, while some life-threatening diseases may require hospitalization.

Many infectious diseases, such as measles and chickenpox, can be prevented with vaccines. Frequent and complete hand washing also protects you from most infectious diseases.

Symptoms of infectious diseases

Each infectious disease has its specific signs and symptoms. The general signs and symptoms common to several contagious diseases include:

  • Fever.
  • Diarrhea.
  • Fatigue.
  • Muscle pains.
  • Tos.
  • When to see a doctor

Seek medical attention if you:

  • An animal has bitten it.
  • They are having trouble breathing.
  • They have been coughing for more than a week.
  • You have a severe headache with a fever.
  • You experience a rash or swelling.
  • You have an unexplained or prolonged fever.
  • You have sudden vision problems.


Infectious diseases can be caused by:


Bacteria: these unicellular organisms are responsible for diseases such as streptococcal pharyngitis, urinary tract infections, and Tuberculosis.

Viruses: even smaller than bacteria, viruses cause many diseases, from the common cold to AIDS.

Fungi: many skin diseases, such as ringworm and athlete’s foot, are caused by fungi. Other types of fungi can infect your lungs or nervous system.

ParasitesMalaria is caused by a tiny parasite transmitted by the bite of a mosquito. Other parasites can be sent to humans from animal feces.

Direct contact

An easy way to detect most infectious diseases is to contact a person or animal with the infection. Three ways in which infectious diseases can spread through direct contact are:

Person to person: a common way of spreading infectious diseases is by directly transferring bacteria, viruses, or other germs from one person to another. This can happen when an individual with the bacteria or virus touches, kisses or coughs, or sneezes on someone who is not infected.

These germs can also be spread through the exchange of bodily fluids through sexual contact. The person who passes the embryo may not have symptoms of the disease but may simply be a carrier.

Being bitten or scratched by an infected animal, even a pet, can make you sick, and, in extreme circumstances, it can be fatal. The handling of animal waste can also be dangerous. For example, you can get a toxoplasmosis infection by removing your cat’s litter box.

Mother to the unborn child: a pregnant woman can transmit germs that cause infectious diseases to her unborn baby. Some germs can pass through the placenta. The germs in the vagina can be passed on to the baby during birth.

Indirect Contact

Disease-causing organisms can also be transmitted through indirect contact. Many germs can remain in an inanimate object, such as a table handle, door handle, or faucet.

When you touch a door handle handled by someone sick with the flu or a cold, you can pick up the germs left behind. If you then touch your eyes, mouth, or nose before washing your hands, you may become infected.

Insect bites

Some germs depend on insect carriers, such as mosquitoes, fleas, lice, or ticks, to pass from one host to another. These carriers are known as vectors.

Mosquitoes can carry the malaria parasite or West Nile virus, and deer ticks can transmit the bacteria that causes Lyme disease.

Food contamination

Another way disease-causing germs can infect it is through contaminated food and water.

This transmission mechanism allows germs to spread to many people through a single source. E. coli, for example, is a bacterium present in or in certain foods, such as undercooked hamburgers or unpasteurized fruit juices.

Risk factor’s

While anyone can get infectious diseases, they are more likely to get sick if their immune systems do not work correctly. This can happen if:

You take steroids or other medications that inhibit your immune system, such as anti-rejection medications for a transplanted organ.

  • You have HIV or AIDS.
  • You have specific cancer or other disorders that affect your immune system.

In addition, certain other medical conditions may predispose you to infection, including implanted medical devices, malnutrition, and extremes of age, among others.


Most infectious diseases have only minor complications. But some infections, such as pneumonia, AIDS, and meningitis, can be life-threatening.

Some types of infections have been linked to an increased risk of cancer in the long term:

  • The human papillomavirus is related to cervical cancer.
  • Helicobacter pylori are related to stomach cancer and peptic ulcers.
  • Hepatitis B and C have been linked to liver cancer.

In addition, some infectious diseases can be silenced and reappear in the future, sometimes even decades later. For example, someone who has had a varicella infection can develop herpes zoster much later.

Prevention of infectious diseases

Infectious agents can enter your body through:

  • Contact with skin or injuries.
  • Inhalation of germs in the air.
  • Ingestion of contaminated food or water.
  • Stings of ticks or mosquitoes.
  • Sexual contact

Follow these tips to decrease the risk of becoming infected yourself or others:

Wash your hands: this is especially important before and after preparing food, before eating, and after going to the bathroom. And try not to touch your eyes, nose, or mouth with your hands, as it is a common way for germs to enter the body.

Vaccinate: Immunization can drastically reduce the chances of getting many diseases. Be sure to keep up with your recommended immunizations and your children’s.

Stay home: when you are sick, do not go to work if you are vomiting, have diarrhea or have a fever. Do not send your child to school if they have these signs and symptoms.

Prepare food safely: keep countertops and other kitchen surfaces clean when preparing meals. Cook foods at the proper temperature with a food thermometer to verify they are cooked.

Also, refrigerate leftovers quickly: do not let cooked foods stay at room temperature for long periods.

Practice safe sex: always use condoms if you or your partner have a history of sexually transmitted infections or high-risk behavior.

Do not share personal items: use your toothbrush, comb, and razor. Avoid sharing glasses or utensils to eat.

Travel wisely: if you are traveling outside the country, talk to your DoctorDoctor about any special vaccinations, such as yellow fever, cholera, hepatitis A or B, or typhoid fever, that you may need.


Your DoctorDoctor may order laboratory tests or image scans to help determine what is causing your symptoms.

Lab tests

Many infectious diseases have similar signs and symptoms. Samples of your bodily fluids can sometimes reveal evidence of the particular microbe causing your infection. This helps your DoctorDoctor adapt your treatment.

Blood test: a technician obtains a blood sample by inserting a needle into a vein, usually in your arm.

Urine tests: this painless test requires you to urinate inside a container. To avoid possible contamination of the sample, you may be instructed to clean your genital area with an antiseptic pad and collect the urine in the middle of the stream.

Throat smear: samples from your throat or other moist areas of your body can be obtained with a sterile swab.

Stool sample: You may be instructed to collect a stool sample so that a laboratory can verify the model for parasites and other organisms.

Lumbar puncture (lumbar puncture): This procedure obtains a sample of your cerebrospinal fluid through a needle carefully inserted between the bones of the lower spine. Usually, you will be asked to lie on your side with your knees raised toward your chest.

Image Scans

Imaging procedures, such as x-rays, CT scans, and magnetic resonance imaging can help identify diagnoses and rule out other conditions causing your symptoms.


A small tissue sample is taken from an internal organ for analysis during a biopsy. For example, a lung tissue biopsy can be checked to detect a variety of fungi that can cause a type of pneumonia.

Treatment of infectious diseases

Knowing what type of germ is causing your disease makes it easier for your DoctorDoctor to choose the proper treatment.


Antibiotics are grouped into “families” of similar types. The bacteria also come together in groups of similar types, such as streptococcus or E. coli.

Certain types of bacteria are especially susceptible to particular classes of antibiotics. The treatment can be more specific if your DoctorDoctor knows what kind of bacteria is fighting.

Antibiotics are usually reserved for bacterial infections because these medications do not affect diseases caused by viruses. But sometimes, it’s hard to know what kind of germ is working.

For example, some types of pneumonia are caused by viruses, while bacteria cause others.

The excessive use of antibiotics has caused several types of bacteria to develop resistance to one or more varieties of antibiotics. This makes these bacteria much harder to treat.


Medications have been developed to treat some, but not all, viruses. Examples include the viruses that cause:

  • VIH / SIDA.
  • Herpes.
  • Hepatitis B.
  • Hepatitis C.
  • Influenza.


Topical antifungal medications can be used to treat infections of the skin or nails caused by fungi. Some fungal infections, such as those that affect the lungs or mucous membranes, can be treated with an oral antifungal.

Fungal infections of more severe internal organs may require intravenous antifungal medications, especially in people with weakened immune systems.


Some diseases, including Malaria, are caused by tiny parasites. Although there are medications to treat these diseases, some varieties of parasites have developed resistance to drugs.

Lifestyle and Home Remedies

Many infectious diseases, such as colds, will resolve on their own. Drink plenty of fluids and get plenty of rest.

Alternative medicine

It has been claimed that several products help to defend against common diseases, such as the cold or the flu. While some of these substances appear promising in the initial trials, the follow-up studies may have had negative or inconclusive results. More research is needed.

Some of the substances that have been studied to prevent or shorten the duration of infection include:

  • Blueberry.
  • Echinacea.
  • It.
  • Ginseng.
  • Goldenseal.
  • Vitamin C.
  • Vitamin D.
  • Zinc.

Check with your DoctorDoctor before trying any product that promises to boost your immune system or scare off colds and other diseases.

Some of these products may cause allergic reactions or interact adversely with other medications you are taking.

Preparing for your Appointment

You may see your primary care doctor first. Depending on the severity of your infection and which of your organ systems is affected by the disease, your DoctorDoctor can refer you to a specialist.

For example, a dermatologist specializes in skin conditions, and a pulmonologist treats lung disorders.

You may want to write a list that includes:

  • Detailed descriptions of your symptoms.
  • Information about medical problems you have had.
  • Information about the medical issues of their parents or siblings.
  • All the medications and dietary supplements you take.
  • Questions you want to ask the DoctorDoctor.

Preparing a list of questions for your DoctorDoctor will help you make the most of your time together. For infectious diseases, some basic questions for your DoctorDoctor include:

  • What is the most likely cause of my symptoms?
  • Are there other possible causes for my symptoms?
  • What kind of tests do I need?
  • Is my condition probably temporary or long-lasting?
  • What treatment do you recommend?
  • I have these other health conditions. How can I better manage these conditions together?
  • Is there a generic alternative to the medication you are prescribing?
  • Are there brochures or other printed material that I can take home? What websites do you recommend?

What to expect from your doctor doctor

Your DoctorDoctor may ask you a series of questions, including:

  • When did your symptoms start?
  • Do your symptoms appear and disappear, or do you have symptoms all the time?
  • How severe are your symptoms?
  • Have you recently had contact with someone who is sick?
  • Have you been bitten or scratched by an animal or come into contact with animal feces?
  • Do you have insect bites?
  • Have you eaten undercooked meat or unwashed vegetables?
  • Have you been out of the country recently?

Infections that Changed the World

Along with natural disasters, infectious diseases are among the leading unintentional causes of death and human suffering worldwide. Some disorders have left their mark on the human race, distorting the course of human history in its path.

In some instances, such as the Bubonic Plague, population levels were drastically reduced for centuries afterward. In other cases, such as Poliomyelitis, the infection of a recognized individual led to greater recognition of a disease and the need for a cure.

Over Bubonic

The Bubonic Plague (also known as the ” Black Death “) spread through Europe from east to west during the 14th century. The Yersinia pestis bacterium was responsible for the epidemic and used oriental rat fleas as intermediaries to reach the human population.

The rats, which carried infected fleas, traveled west along the Silk Road and on boats across the Mediterranean. The Bubonic Plague demonstrated from the beginning how human advances in trade and commerce could fatally spread a pathogen.

The name of the plague comes from the Latin word bubo, which refers to a boil or abscess. The symptoms were horrible. They started with a fever and sweating but progressed to a blue-black boil in the groin.

If boils were not cut, they would grow, and people would die from toxic buildup. In the same way, the puncture of the bulls was often as deadly and could lead the pathogen to fly.

The mortality rate for this disease was more than 70 percent, killing up to 200 million throughout Europe and reducing the continent’s population by half. Historians believe that the spread of the Bubonic Plague contributed to the fall of the feudal economic system and caused irreparable damage to the church.

Many priests became infected after performing the last rites and funeral services. He even retired from his parishes, fearful of contracting the plague.

The Bubonic Plague is among the most horrible diseases in history, even when the development of antibiotics has limited the contemporary occurrences of the Black Death.


When Europeans first arrived in the New World in the late 15th and early 16th centuries, they used advanced military techniques to conquer North America and South America in a hurry.

But they also brought smallpox, which played an instrumental role in killing Native Americans. Old World Europeans had a long history of living in enclosed places with domesticated animals and eating and drinking from similar sources.

This led to the spread of many diseases. But those who survived developed an impressive immunity to pathogens that would otherwise be deadly.

These individuals were among the first settlers in America who brought smallpox to the continents in 1520. In conjunction with other diseases of the Old World, such as influenza and measles, smallpox killed almost 90 percent of the indigenous population, overcoming the damage done by the late medieval war.

Smallpox was also an agent of vicious deformation, leaving infected people with visible sores on their bodies.

Moving forward several centuries, smallpox is one of two diseases (the other is rinderpest) that must be eradicated from the human population due to vaccination efforts. Today, smallpox can only be found in overly protected laboratory environments.

Spanish Influenza

The 1918 flu pandemic was caused by one of the most lethal pathogens of the 20th century, infecting 500 million people worldwide. Outbreaks in the United States and Europe soon spread throughout the world.

Although this deadly flu strain devastated population centers indiscriminately, it quickly earned the nickname ” Spanish influenza ” as Spain was hit especially by the virus. Even King Alfonso XIII of Spain contracted it.

Spanish influenza had a remarkable effect on the battlefields of World War I as it infected many young, otherwise healthy individuals. Records suggest that more Americans died from the 1918 flu than the fighting on the front lines.

Fifty percent of the US Navy’s military. UU contracted the flu. Almost as many in the US Army. UU

They were also affected. The effects of the flu were felt throughout the economy and the army, and many believe that the outbreak influenced the direction of World War I by infecting the militias and destroying the medical infrastructure.


Today, Polio is extremely rare, with relatively few cases in the industrialized world since Jonas Salk developed a vaccine against Polio. Before creating a vaccine, Polio was easily transmitted in the feces of an infected individual or by droplets when sneezing.

Polio is usually asymptomatic. However, when symptoms do occur, they can be debilitating. The disease is notorious for paralyzing its victims, which requires them to live the rest of their lives in iron lungs.

The paralysis caused by Polio can not be reversed. Although mobile generators can help some afflicted, others still depend on the iron lungs that became famous in the 1940s.

The most well-known person who suffered paralysis from Polio was the former president of the United States, Franklin D. Roosevelt. His efforts to combat the stigma of the disease affected all aspects of the presidency in the years before and after the Second World War.

Ultimately, this changed how a man and a nation view the disease that causes paralysis and subsequent disability.


There are four stages of Syphilis, a sexually transmitted disease that first appears with a soft chancre at the site of infection. Secondary Syphilis occurs with a generalized rash and swelling of the lymph nodes.

Then, the bacteria enter a latent stage before appearing as tertiary Syphilis, which causes neuromuscular degeneration, blindness, and dementia. Historians are not sure how Syphilis managed to establish itself in European populations, but the leading hypothesis says that it was the importation from the colonization of the New World.

Syphilis has ruined many famous people, including several members of the medieval papacy. In 1508, Julius II could not be kissed by other Christians because he was covered in syphilitic sores.

Syphilis also had a long history of worthless medical remedies, such as the use of mercury, which often left the infected worse. Nowadays, Syphilis is still widespread, although it can often be cured with penicillin.


Few diseases have led to the stigma of the human immunodeficiency virus (HIV), which becomes the acquired immunodeficiency syndrome (AIDS). Scientists believe that the virus went from primates to humans in Africa at the beginning of the 20th century.

However, the disease did not gain traction in popular culture until the early 1980s, when several homosexual men in New York and California exhibited strange cases of pneumonia and cancer.

Their initial association with homosexual men gave rise to the initial name “related to homosexuals” immune deficiency “(GRID).

Paranoia spread throughout Europe and the United States as individuals were unsure how they were responsible for spreading the disease.

The association of HIV with the homosexual community led to the development of activist groups such as ACT UP, which helped boost the early defense of LGBT people and solidified the eventual rights for sexual minorities decades later.


Tuberculosis (TB) is a deadly respiratory infection that can take two forms: latent TB and active TB. Latent TB is not contagious, and one’s immune system can often fight against it.

One-third of the world’s population has latent TB. In weakened immune systems, active TB can take hold.

Symptoms include episodes of cough, severe chest pain, night sweats, and loss of appetite. The increase in HIV / AIDS is related to TB cases since weakened immune systems have an almost impossible time-fighting bacteria that would otherwise be dormant.

Tuberculosis left its mark on science in more than one way. In the 19th century, TB was often spread through milk. This led to discontinuous pasteurization, a method of low-temperature pasteurization that has its roots in eradicating Tuberculosis in dairy products.


Malaria is a mosquito-borne disease caused by parasites that leave people infected with flu-like symptoms. Malaria remains one of the most severe killers globally, infecting more than 200 million in 2016 and killing nearly 500,000.

The common claim of the fame of Malaria is its possible role in killing Alexander the Great. But did you know that Malaria and resistance to it helped in the brutal transatlantic slave trade? There is no evidence of Malaria in precolonial America, and therefore its introduction wreaked havoc on native populations.

This led the first European populations to search the plantations of South America for the people of Africa, who were resistant to Malaria if they survived the disease when they were children.

As Malaria spread like wildfire through the southern United States, killing Native Americans, Africans were forced into the slave trade.

From the medical point of view, Malaria provided scientists with a fundamental understanding of transmission vectors, including how disease-carrying animals can infect human populations and what can be done to stop them.


Few diseases have fueled hysteria, such as Ebola, only discovered in Africa in the late 1970s. Ebola, short for Ebola hemorrhagic fever (EHF), is a virus that leads to severe bleeding in humans and other primates.

The symptoms may take several days or weeks to develop. They include sore throat, muscle pain, vomiting, diarrhea, and possible internal and external bleeding. According to the strain, Ebola has a high mortality rate, killing almost half of those infected.

However, mortality rates can reach up to 90 percent. The most lethal Ebola outbreak spread from West Africa in March 2014. It killed five times more individuals than all previous outbreaks combined.

Cases were reported in the United States and Europe (including the United Kingdom, France, Germany, and Spain). The total containment of the virus did not occur until 2016. Its dissemination and sequelae proved the capacity of the World Health Organization drastically to respond to a modern pandemic.


In the worst case, cholera can go from asymptomatic to fatal in less than three hours. Cholera is a diarrheal disease caused by a bacterium that usually spreads through water or food systems that lack adequate sanitation.

Although the roots of the disease were in the Ganges delta in India, Cholera has spread throughout the planet. There have been pandemics in South Asia (1961), Africa (1971), and the Americas (1991).

There are up to four million cholera cases each year, with more than 100,000 deaths. As of July 28, 2010, the United Nations resolved to explicitly recognize drinking water as a human right, a development intrinsically related to the spread of waterborne bacteria.