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Infectious Diseases: Causes, Symptoms, Treatments & Prevention

Infectious Diseases (a.k.a: Transmissible or Communicable or Contagious Diseases) are common illnesses caused by pathogens. They can be mild infections that resolve without any treatment and severe infections that can even lead to death.

Infectious Diseases

They account for 15 million to 57million deaths per annum globally. Pathogens are highly adaptable in humans because of their replicative and mutational capacities making the treatment difficult for severe infections. However, many infections are preventable with vaccinations or other measures.

What are Infectious Diseases?

Infectious diseases occur due to various pathogens such as bacteria, virus, or fungi. Different pathogens and common infections caused by them are given below:

Type of Pathogen
Common Infectious Diseases
BacteriaTuberculosis, Staph infections, pneumonia, urinary tract infection
VirusCommon cold, flu, hepatitis viruses, HIV
FungiAthlete’s foot, Jock itch
ParasitesMalaria, pinworm infections

Initial infection occurring in a healthy person is called primary infection whereas new infection occurring in a patient with weak immunity (due to primary infection) is called secondary infection.

What Causes Infectious Diseases?

The pathogen can enter into the body through different modes such as penetration, inhalation, or through blood. After entering into the body, it attaches to the specific tissue (depends on type of pathogen) within the body. In the body, pathogen produces toxins, multiplies, and damages the host tissue leading to symptoms.

Infectious diseases can be divided into different stages based on the progression of the infection in the body:

  1. Incubation Period: It is the time period between initial contact of pathogen and the onset of signs and symptoms.
  2. Prodromal Period: In this phase, the patient may have mild to moderate symptoms.
  3. Invasive Period or the Period of Illness: In this phase, the symptoms worsen and toxicity levels are high.
  4. Convalescence Period: It is recovery or healing period from infection.

Infections can spread through different modes of transmission. Common modes of transmission are:

  • General Transmission: Air (spores), water (contamination), insects such as mosquitoes, flies, or animals such as rats can transmit the infection to human beings.
  • Human to Human Transmission: It can be of different types such as:
    • Direct Contact: Transmission from infected to healthy person through touching, kissing, and through sexual intercourse.
    • Indirect Contact: Transmission from coming in contact with contaminated surfaces, sharing needles, and touching open wound.
    • Droplet Transmission: Transmission by inhalation of air droplets released by the infected patient through coughing or sneezing.
    • Fecal-oral Transmission: Transmission of ingestion of contaminated food and water.
    • Mother to Fetus Transmission: Transmission of infection from pregnant women to unborn child.

Symptoms of Infectious Diseases:

Symptoms of infectious diseases depend on the pathogen causing the disease. However, there are few common symptoms that may occur due to the infection are:

  • Fever
  • Chills
  • Cough
  • Diarrhea
  • Rashes
  • Muscle weakness
  • Nausea or vomiting
  • Tiredness
  • Headache
  • Lack of appetite

Seek medical attention immediately, if symptoms persist for more than 10 days.

Infections can be acute or chronic depending on the duration of symptoms.  Symptoms of acute infections have rapid onset and last for  1 to 4 weeks. Symptoms of chronic infections develop slowly and last for more than 4 weeks.

Risk Factors of Infectious Diseases:

Persons with low immunity are highly susceptible to infectious diseases. Decrease in immunity occurs due to various factors such as:

  • Age
  • Immunosuppressive diseases such as HIV and cancer
  • Immunosuppressive medications such as steroids and anticancer agents
  • Not getting vaccinated
  • Stress
  • Surgical procedures

Genetic factors also act as a predisposing factor for infectious diseases. Consuming unbalanced diet and living in crowded areas due to poor socioeconomic status also increases the risk of infectious diseases.

Complications of Infectious Diseases:

Infections can be self-limiting and resolve with treatment. However, some of the infections are life-threatening such as HIV, pneumonia, dengue, and tuberculosis. Infectious diseases can also cause cancer. Human papillomavirus (HPV) can cause cervical cancer and hepatitis can cause liver cancer.

Diagnosis of Infectious Diseases:

The healthcare provider initially obtains the epidemiological data and evaluates the signs and symptoms. Epidemiological data include time and location of occurrence of infection and vector that transmitted the infection.

To evaluate the signs and symptoms, physical examination is performed. During physical examination, the healthcare provider observes for signs of redness or swelling, palpates to detect pain or tenderness, and measures vital signs (heart rate, blood pressure, respiratory and temperature).

Blood tests are performed to determine the complete blood count, especially lymphocytes (elevate in case of infection).

Pathogen can be identified through gram staining technique and culture test using a sample of urine, feces, sputum, pus, or cerebrospinal fluid depending on the type of infection. Sputum can be obtained using throat swab and cerebrospinal fluid can be obtained using lumbar puncture technique or spinal tap. Polymerase chain reaction (PCR) also helps in detecting the pathogen or antibodies against the pathogen.

Imaging tests such as X-ray and computed tomography (CT) scan can be performed if the infection is severe such as in tuberculosis and meningitis.

Endoscopy and biopsy can also be performed in few cases depending on the type of infection.

Treatments for Infectious Diseases:

Some infections such as sore throat and common cold are self-limiting whereas some infections require treatment. Treatment depends on the type of infection and causative organism. Treatment can be given to treat the symptoms and kill the pathogen. Infections can be treated by:

  • Antibiotics (for bacterial infections) & antitubercular (for tuberculosis)
  • Antiviral agents (for viral infections)
  • Antifungal agents (for fungal infections)
  • Antiparasitic drugs (for protozoal and helminthic infections)

These treatments are available in oral, topical, or injection form. Depending on the type and severity of infection, route of administration is determined.

Prevention of Infectious Diseases:

Preventive measures can decrease the incidence of infectious diseases. Therefore, following measures  can be taken:

  • Get vaccinated.
  • Maintain a healthy lifestyle.
  • Consume healthy diet rich in nutrition.
  • Maintain personal hygiene.
    • Cover your nose and mouth while coughing or sneezing.
    • Use a sanitizer or wash hands with antiseptic hand wash before and after eating, while preparing food, after using toilets, after coughing or sneezing, after handling pets, and after caring for a patient.
    • Use disinfectants for sanitation and hygiene.
  • Don’t share your belongings such as towel, brush, and razor with others.
  • Vaccinate your pets.
  • Be cautious with sick animals.
  • Practice safe sex. Use condoms and avoid sex with anonymous persons.
  • Stay at home if you are sick.
  • Be cautious while travelling to other states or country. Get any special vaccinations if necessary, by talking to your doctor.

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