Infections

Introduction – infections and infectious diseases

Infections are diseases that occur when harmful microorganisms (pathogens) enter the body from the environment, where they begin to reproduce and trigger a reaction. The most common causes of infection are viruses, bacteria, fungi, and parasites. Infectious diseases can be transmitted from person to person, through contaminated food, water, and insect bites. Some infectious diseases have mild symptoms, while others can be very serious, even life-threatening.

Infectious diseases are extremely common worldwide, although some occur more frequently than others. Common viral and bacterial infections include the common cold, influenza, gastroenteritis, gastritis, food poisoning, ear infections, pneumonia, sinusitis, and throat infections. Symptoms vary depending on the microorganism causing the infection, but high temperature and fatigue are most common. Mild infections can be managed with rest and over-the-counter medication, while more severe infections, especially those that are life-threatening, may require hospitalization.

Many infectious diseases, such as measles, mumps, and rubella, can be prevented through vaccination. Personal hygiene and maintaining cleanliness in workspaces and homes also play an important role in prevention. Bacterial infections are treated with antibiotics, while these drugs are never used to treat viral infections. The overuse of antibiotics leads to bacterial resistance to these drugs, making the treatment of infections more challenging.

What is an infection?

An infection is a disease caused by harmful microorganisms (pathogens) that enter the body from the outside, such as viruses, bacteria, fungi, parasites, and very rarely prions. Infection can be acquired from other people, insect bites, and contaminated food or water. Influenza, measles, HIV, strep throat, COVID-19, and salmonella are all examples of infectious diseases.

Difference between infectious and non-infectious diseases

Unlike infectious diseases, non-infectious diseases are not caused by organisms that come from the outside but rather by genetics, anatomical differences, aging, and the person’s living environment. This means that a person will not acquire a non-infectious disease through insect bites or consuming contaminated food. Examples of non-infectious diseases include cancer, diabetes, congestive heart failure, and Alzheimer’s disease.

Causes of infectious diseases

Infectious diseases can be caused by viral, bacterial, parasitic, or fungal infections. There is also a rare group of infectious diseases known as transmissible spongiform encephalopathies (TSE).

Viral infections

A virus consists of nucleic acid, either DNA or RNA, surrounded by a protein coat. It requires a living cell to replicate. Depending on the symptoms, viral infections can be asymptomatic (without visible symptoms), mild, or very severe.

Viral infections

A virus consists of nucleic acid, either DNA or RNA, surrounded by a protein coat. It requires a living cell to replicate. Depending on the symptoms, viral infections can be asymptomatic (without visible symptoms), mild, or very severe.

Fungal infections

Like bacteria, there are many different types of fungi. They can live within or outside the body. When fungi overgrow in the body or when harmful fungi enter the body through the mouth, nose, or a cut in the skin, they can cause a fungal infection.

Parasitic infections

Parasites use the bodies of other organisms to live and reproduce. Parasites include worms (helminths) and some single-celled organisms (protozoa).

Transmissible spongiform encephalopathies (TSE/prion diseases)

TSE is caused by prions, which are altered proteins that cause other proteins in the body, mainly in the brain, to become altered as well. The body is unable to utilize or eliminate these proteins, so they accumulate and lead to neurodegenerative disease. Prions are an extremely rare cause of infectious diseases.

Symptoms of infection

The symptoms of infectious diseases depend on the type of illness. Fungal infections usually cause symptoms in specific areas of the body, such as rash and itching. Viral and bacterial infections can present with similar symptoms, such as fever, chills, cough, fatigue, muscle aches, and headache. Gastrointestinal symptoms like diarrhea, nausea, and vomiting may also accompany these infections.

IMPORTANT: Visit a doctor if you have symptoms of an infection that do not go away or if they worsen over time.

Common symptoms associated with infections

Symptoms of bacterial infections

• Fever
• Chills
• Fatigue
• Headache
• Skin – Redness, blisters, ulcers, swollen or painful skin.
• Digestive tract – Diarrhea, abdominal pain, nausea, vomiting.
• Lungs – Cough, shortness of breath, chest pain, mucus (sputum).
• Meningitis (inflammation of the membranes surrounding the brain) – Neck stiffness, nausea or vomiting, sensitivity to light, confusion.
• Bloodstream and sepsis: High temperature, weakness, sweating, low blood pressure
• Heart (endocarditis) – High fever, chest pain, night sweats, shortness of breath, cough, muscle, joint pain.

Symptoms of viral infections

• Flu-like symptoms: fever, pain in the head and body, fatigue, sweating.
• Symptoms of the upper respiratory tract: sore throat, cough, sneezing.
• Lungs: headache, shortness of breath, muscle pain, severe cough.
• Digestive tract: nausea, vomiting, diarrhea.
• Heart (myocarditis): Pain and pressure in the chest, shortness of breath, difficulty breathing, palpitations, headache, fluid retention in the body.

Types of infections

Bacterial infections

-Campylobacter and Salmonella infections, common types of bacterial food poisoning.
-Cellulitis, abscesses, impetigo, skin infections.
-Streptococcus, including ear and sinus infections and some types of pneumonia.
-Lyme disease, a disease transmitted by ticks.
-Bacterial vaginosis, an overgrowth of bacteria in the vagina.
-Chlamydia and gonorrhea, sexually transmitted infections.
-Bacterial throat infection, common in children causing sore throat.
-C. difficile (Clostridium difficile), an intestinal infection.
-E. coli, a common cause of urinary tract infections (UTIs).

Viral infections

Respiratory infections

Examples:

• Common cold (usually caused by rhinovirus).
• Influenza (flu).
• COVID-19.
• Respiratory syncytial virus (RSV).
• Human metapneumovirus (hMPV).
• Parainfluenza.

Viral infections in the digestive system

These include:

• Norovirus, rotavirus and astrovirus can cause gastroenteritis, sometimes referred to as “stomach flu.”
• Hepatitis viruses cause liver disease. These infections often last for a long time (chronic).

Viral hemorrhagic fevers

Examples:

• Ebola.
• Hantavirus pulmonary syndrome.
• Dengue.
• Yellow fever.

Sexually transmitted viruses

Examples:

• Human immunodeficiency virus (HIV).
• Human papillomavirus (HPV)/genital warts.
• Genital herpes (HSV).
• Hepatitis B.

Exanthematous viral infections

Examples:

• Chickenpox.
• Measles.
• Rubella (German measles).
• Roseola.
• Fifth disease.
• Mumps.

Neurological infections

Examples:

• West Nile virus
• Polio
• Rabies

Congenital viral infections

Examples:

Cytomegalovirus (CMV). Cytomegalovirus (CMV) is a very common virus from the herpes virus family. Cytomegalovirus spreads from person to person through body fluids, such as blood, saliva, urine, sperm and breast milk. Congenital cytomegalovirus (CMV) infection occurs when the virus passes the placenta during pregnancy and infects the fetus. The highest risk of fetal infection is in mothers who have a primary infection during the first and second trimesters of pregnancy.

Rubella. Rubella virus (RV) is a virus of the genus Rubi virus, which is transmitted by droplets excreted from the respiratory secretions of infected individuals. Congenital rubella syndrome (CRS) is a disease in newborns that results from infection of the mother with rubella virus during pregnancy. When rubella infection occurs during early pregnancy, it can lead to serious consequences – such as miscarriages, stillbirth, and severe congenital defects in newborns.

The Zika virus. Zika virus (ZIKV) is a flavivirus (Flaviviridae family), an RNA virus primarily transmitted by aedes mosquitoes. The risk of a pregnant woman getting a primary infection is the same as in other adults. The symptoms of Zika infection are generally mild and last for two to seven days. Symptoms vary and may include rashes, low fever, conjunctivitis, muscle and joint pain, arthritis, fatigue, and headache. But at greatest risk are women who become infected during pregnancy, because it poses a risk of congenital Zika infection and possible birth defects in the fetus.

How do infections occur?

The mouth, nose, and cuts on the skin are common entry points for pathogens into the body. Diseases can spread:

– from person to person by coughing and sneezing. In some cases, droplets produced by coughing or sneezing can remain in the air
– by kissing, or sexual contact
– by sharing utensils or cups with other people
– over surfaces such as doorknobs, telephones, and worktops
– by contact with the feces of an infected person or animal
– by stings or bites of insects and animals
– through contaminated or improperly prepared food or water
– through contact with contaminated soil or sand (such as gardening)
– through infected blood, from blood transfusions, organ/tissue transplantation or other medical procedures.

Diagnosis of infections

To diagnose an infectious disease, a doctor may use one or more laboratory tests, as well as imaging techniques such as X-rays, magnetic resonance imaging (MRI), or CT scanner. Some test results, like a nasal swab or urine sample analysis, can be obtained quickly, while tests for suspected bacterial infections may take longer as the bacteria need to be cultured in the laboratory before obtaining test results (antibiogram).

Common tests that are performed include:

Nasal or throat swab: A nasal or throat swab can help the doctor diagnose the type of infection to determine the best treatment approach. After taking the swab, the sample is placed on culture media in the laboratory to check for the growth of microorganisms, the causative agents of inflammation.

Blood tests: They can detect whether the infection is viral or bacterial. A blood sample is taken from the finger or vein in the arm to analyze the white blood cell count, including lymphocytes, neutrophils, and monocytes, as well as red blood cells and platelets. Neutrophils are the most abundant type of white blood cells, and their count increases in the case of a bacterial infection. On the other hand, in a viral infection, the number of lymphocytes typically rises. In some cases, it may be important to measure the level of C-reactive protein (CRP), which indicates an inflammatory process in the body and often points to a bacterial infection.

Blood culture or Hemoculture is a test that checks for the presence of pathogens, bacteria, and fungi in blood samples. During this test, a blood sample is kept in special laboratory conditions to check if the bacteria are growing. Hemoculture testing is often used to diagnose infections and determine if pathogens have entered the bloodstream.

Urine tests: Urine sample analysis can detect urinary tract infections. Laboratory analysis determines the presence of white blood cells, red blood cells, or bacteria. A doctor may also request a urine culture, which involves culturing the urine sample on culture media in the laboratory to check for the growth of microorganisms causing urinary tract infections. It is commonly performed when a bacterial infection of the urinary tract is suspected.

Stool tests: Laboratory analysis to detect the presence of bacteria or parasites in the stool. The sample is tested in the laboratory on special culture media where, in the case of infection, microorganisms will grow.

Sputum test: A test that detects the presence of bacteria and fungi originating from the lower respiratory tract.

Skin or tissue samples: Some bacterial and fungal infections can be diagnosed by taking a sample from the affected area using a swab, which is then placed in a test tube and sent to the laboratory for analysis.

Cerebrospinal fluid (CSF) collection: Cerebrospinal fluid is the colorless, odorless fluid that surrounds the brain and spinal cord. A lumbar puncture is a procedure in which a sample of CSF is taken using a needle. It is performed when meningitis or encephalitis is suspected.

Cervical cells (Pap test): A swab is taken from the vagina and cervix for analysis to detect precancerous and cancerous changes, as well as HPV infections.

Imaging (X-ray, CT scan, or MRI) of affected body parts: Depending on the affected area of infection and the results of other analyses, as well as the physician’s assessment, X-rays, CT scans, or magnetic resonance imaging (MRI) may be performed to precisely visualize the location and extent of the infection.

 

Biopsy: During a biopsy, a small sample of tissue is taken from an internal organ for testing. For example, a lung tissue biopsy can be examined for various fungi that may cause a type of pneumonia.

Treatment of infections

The treatment depends on the type of microorganisms causing the infection. In some cases, the doctor may initially recommend monitoring the symptoms of the infection before deciding on the treatment approach.

Bacterial infections are treated with antibiotics, and the choice of antibiotic depends on the bacteria isolated in the laboratory. The problem in antibiotic treatment is the development of bacterial resistance to these drugs, which arises from the excessive use of antibiotics. Antibiotic resistance makes some bacterial infections very difficult to treat and therefore more life-threatening. It is important to take antibiotics only when prescribed by a doctor.

Most viral infections are treated with over-the-counter medications. For certain viral infections, specific medications are available, such as antiviral drugs for hepatitis B and C, herpes, or antiretroviral therapy for HIV.

Fungal infections are treated with antifungal medications. They can be taken orally or applied topically as creams to the affected area of the skin. Severe fungal infections of internal organs, especially in individuals with weakened immune systems, may require intravenous antifungal drugs.

Antiparasitic – Some diseases, such as malaria, are caused by tiny parasites. Although there are drugs to treat these diseases, some types of parasites have developed drug resistance.

There is no treatment for prion diseases.

Home treatment

During the treatment of infections, it is important to drink plenty of fluids and get rest. For respiratory infections, remedies such as cranberry tea, rosehip tea, and the intake of vitamin C and zinc can be helpful. Herbal supplements like echinacea and propolis may also provide relief.

 

Infection prevention

Preventing infections involves applying simple yet highly effective tips that can help reduce the risk of infections and sometimes even prevent their occurrence.

Immunization against infectious diseases: Vaccines reduce the risk of acquiring infectious diseases by stimulating the immune system to recognize and fight infections. Although people may still get sick from a disease even after receiving a vaccine, the symptoms are usually less severe compared to those who haven’t been vaccinated.

Wash and dry your hands well: Washing your hands thoroughly with water and soap is especially important before preparing a meal or eating, after using the bath, after contact with feces (animal or human) and after working in the garden or in the dirt.  

Take care of hygiene when preparing food: Wash your hands with soap and water before, during and after food preparation. Peel or thoroughly wash all fruits and vegetables. Cook the meat at an appropriate temperature before consuming. Wash surfaces and food preparation utensils with detergent and water after use. Do not eat thermally insufficiently processed foods. Drink only water from the water supply and bottled water. Do not drink unpasteurized milk.

Cover your nose and mouth when sneezing or coughing: If you don’t have a tissue, cough into your sleeve. Wash or disinfect your hands after sneezing or coughing.

Ventilate your home: Poor ventilation in rooms can increase the spread of viruses and bacteria. Regularly open windows to allow fresh air to circulate.

Disinfect surfaces that are frequently touched in your home and workplace: Regular cleaning of household and frequently touched surfaces will help reduce the spread of infections. Some of the frequently used surfaces are tables, benches, door handles, light switches, toys, and faucets.

Avoid close contact: Avoid contact with people who are sick with an infectious disease or those who share personal belongings with them. Also avoid contact with others while you are ill.

Be cautious with water: Do not drink or swim in water if there is suspicion of contamination.

Practice safe sex: Use condoms during any type of sexual activity.

Protect yourself from insects: To reduce the risk of ticks or mosquito bites, use repellent against these insects, cover as much exposed skin as possible with clothing and check for ticks after you have been in the forest or in areas with high grass.

 

Outlook / Prognosis

The duration of an infection depends on its cause, whether it is viral, fungal, or bacterial, and how severe it is. With treatment, most people improve and recover after being infected. A bacterial infection typically lasts three to five days with the use of antibiotics, but in more severe cases, it can last 10 to 14 days.

Viral infections usually last up to seven days. Sometimes infections lead to serious complications, especially in respiratory diseases. People with compromised immune systems are at higher risk of serious complications, but they can also occur in healthy people.

Some diseases, such as HIV and hepatitis B, cannot be cured, but medications can help prevent serious complications. Sexually transmitted infections can cause infertility or even lead to cancer, so it is important to take steps to protect yourself and others.

 

Complications of infections

Complications of infections can be life-threatening, so early diagnosis is key to their prevention. Infection can spread from one site through the bloodstream throughout the body.

Early diagnosis and treatment of infections can prevent complications such as bacteremia, sepsis, and septic shock. Viral infections can also cause sepsis. These are serious life-threatening conditions that require urgent treatment. The elderly, immunocompromised individuals, those with heart disease, diabetes, chronic obstructive pulmonary disease, patients after surgery, or those with catheters during treatment are at risk for these infections.

Complications of viral infections can include pneumonia, viral meningitis, encephalitis, cancer, and more. If fungal skin infections are left untreated, they can persist for a long time. They can also spread to other parts of the body, cause bacterial infections, or be transmitted to other people.

 

When to visit a doctor

If you have any symptoms of an infectious disease that do not go away or worsen, it is important to visit a doctor. In the case that, during the examination and analysis, the doctor determines that you have a bacterial infection, they may prescribe antibiotics. If you have a chronic infection, frequent check-ups with the doctor can help keep the condition under control. You may also need vaccines for travel to certain countries, which is another reason to consult with a doctor.

 

When to urgently visit a doctor

These symptoms are indications for an urgent visit to the doctor:

• High fever or very low body temperature accompanied by chills and severe shaking
• Swelling in the joints or legs
• Confusion, loss of consciousness, or seizures
• Rapid or irregular heartbeat
• Scanty urination or absence of urination
• Difficulty breathing
• Dizziness or weakness
• Rash or warm, red skin

 

Conclusion

We live surrounded by viruses, bacteria, fungi, and parasites daily. Some of these microorganisms we encounter can be harmful and cause infections. There are many ways to prevent infectious diseases, such as vaccination, maintaining personal hygiene, and keeping our homes and workspaces clean.

These measures are especially important due to the contact we have with other people who may struggle to fight off infections due to their health condition. If you have symptoms of an infection that doesn’t go away, worsens, or manifests with severe symptoms, seek medical attention. There are effective laboratory tests and modern diagnostic procedures, as well as efficient medications available to detect and treat various infections.