10 Types of infections: Viral, bacterial, fungal, and parasitic
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Summary: Infections are caused by four primary types of pathogens: viruses, bacteria, fungi, and parasites. Viral illnesses, such as influenza, are usually managed with rest or antiviral medications and cannot be treated with antibiotics. Dr Lau, registered GP in Australia mentions however, others (eg. Influenza, COVID-19, hepatitis C and HIV) often require targeted antiviral therapy or hospital care. Bacterial infections, such as strep throat, are typically treated with antibiotics; however, improper use can lead to the development of drug resistance. Fungal infections affect skin, nails, or lungs and require antifungal therapy. Parasitic infections, like malaria or tapeworms, are caused by organisms that live on or inside the body and are addressed with antiparasitic drugs. Understanding these types is crucial for effective prevention and treatment.
Infections are caused by microorganisms that invade the body and disrupts its regular functions. These infectious agents are generally divided into four main types: viral, bacterial, fungal, and parasitic. Each type originates from a distinct pathogen, presents unique signs and symptoms, and requires tailored approaches for detection and treatment. In 2022, more than 15,770 deaths in Australia were attributed to infectious diseases, highlighting the serious impact they can have on public health. Understanding these types is essential for the successful prevention, management, and control of diseases.
Brief overview of what infections are
Infections develop when harmful microorganisms such as viruses, bacteria, fungi, or parasites enter the body and grow, disrupting normal functions and causing illness. These germs may spread through air, contaminated water or food, physical contact, or insect transmission. While the immune system works to combat these intruders, medical treatment is sometimes necessary to clear the infection and avoid further health issues. Dr Lau mentions - It should be noted that humans also coexist with many non-pathogenic microbes that are essential for digestion, skin integrity and immune development.Importance of understanding different types
Recognising the differences between viral, bacterial, fungal, and parasitic infections is crucial for precise diagnosis and proper treatment. Each category responds to specific medications—antibiotics for bacterial infections, antivirals for viruses, antifungal agents for fungal conditions, and antiparasitic drugs for parasitic diseases—so misidentifying an infection can lead to improper care. Understanding these differences also aids in limiting disease transmission, promoting responsible medication use, and reducing the risk of drug resistance and serious health complications.What is a viral infection?
A viral infection is caused by a virus, a tiny infectious agent that require living host cells to reproduce. Once inside the body, the virus invades the healthy cells and exploits their internal systems to reproduce, often harming or destroying the cells in the process. Viral infections can target various parts of the body, including the respiratory system, digestive system, skin, liver, and immune system. Common examples include cold, influenza (flu), COVID-19, hepatitis and HIV. Unlike bacteria, viruses are unresponsive to antibiotics. Instead, treatment typically involves relieving symptoms, boosting the immune system, and sometimes using antiviral medications. Vaccines are one of the most powerful tools for preventing many viral infections. Also read: What are signs that your immune system is fighting a virus?Type of viral infections
Here are different types of viral infections:1. Respiratory viral infections:
They affect the nose, throat, and lungs. Examples include common cold, influenza (flu), COVID-19, and respiratory Syncytial Virus (RSV)2. Gastrointestinal viral infections:
They affect the stomach and intestines, often causing vomiting and diarrhoea. Examples include Norovirus, Rotavirus, and Adenovirus3. Liver viral infections:
They attack liver cells and may cause inflammation or chronic injury. Examples include Hepatitis A, B, and C.4. Nervous system viral infections:
They affect the brain and nerves, sometimes leading to serious complications. Examples include Poliovirus, Viral meningitis, and Encephalitis.5. Skin viral infections:
They cause rashes, sores, or warts on the skin. Examples include Measles, Chickenpox, Shingles, and Warts (caused by HPV)6. Sexually transmitted viral infections:
They spread through sexual contact and may affect various systems. Examples include HIV/AIDS, Human Papillomavirus (HPV), Herpes Simplex Virus (HSV), Hepatitis B7. Systemic viral infections:
They spread throughout the body and affect various organs. Examples include Dengue fever, Cytomegalovirus (CMV), and Ebola.What causes viral infections?
Viral infections are caused by viruses, which are tiny infectious agents consisting of nucleic acids (DNA or RNA) enclosed in a protective shell. These pathogens penetrate the body through various routes, such as the mouth, nose, eyes, skin, or bloodstream and infiltrate healthy cells to multiply. Common transmission routes include:- Airborne droplets from coughs or sneezes
- Direct contact with infected people or surfaces
- Contaminated food or water
- Sexual contact
- Insect bites
Viral infections symptoms
Viral infections can impact various parts of the body, so symptoms vary depending on the virus and the part it affects. However, many viralinfections exhibit similar signs. Typical symptoms include:- Fever
- Headache
- Cough and sore throat
- Fatigue
- Runny nose
- Nausea, vomiting, diarrhoea
- Skin rashes
- Swollen lymph nodes
- Body ache
How viral infections spread?
Viral illnesses are transmitted when viruses pass from an infected person, animal, or surface to another host. This transmission can happen in several ways:- Airborne transmission: Viruses can be spread through airborne droplets released when an infected person sneezes, coughs, or talks.
- Direct contact: Viruses can be transmitted through physical contact with an infected person’s blood, spit, or saliva.
- Contaminated food or water: Consuming food or water contaminated with viruses can lead to infections of the gastrointestinal tract.
- Contaminated surfaces: Some viruses can survive on surfaces. Touching such surfaces and then your mouth, nose, or eyes can spread the virus.
- Insect bite: Some viruses are transmitted by insects like ticks or mosquitoes.
- Sexual contact: Viruses can spread through unprotected sexual activity.
- Mother to baby (vertical transmission): Viruses may be transmitted from a pregnant woman to her baby during pregnancy, childbirth, or while nursing.
Viral infections treatment options
Treating viral infections depends on the specific virus, the severity of the symptoms, and the part of the body involved. Unlike bacterial illnesses, antibiotics are ineffective against viruses. Here are the main treatment options:- Supportive care: Rest, hydration, and over-the-counter medications relieve symptoms like fever or pain.
- Antiviral medications: Specific drugs help slow down or stop the virus.
- Vaccination: Helps protect against various viral infections, such as measles or hepatitis, by supporting the body’s natural immunity.
- Immune support: A balanced diet and sufficient hydration and sleep are beneficial. There is no evidence that over-the-counter ‘immune boosters’ speed recovery.
When to see a doctor or use an online GP service
You should consult a GP or utilise an online Doctor service for a viral infection if you are experiencing a persistent high fever, intense body aches, difficulty breathing, chest discomfort, or if your symptoms worsen after several days. Dial 000 or attend the nearest emergency department for severe breathlessness, chest pain, confusion or collapse. You should also reach out to a doctor if your symptoms persist beyond 10 days, if you are pregnant, elderly, have a compromised immune system, or suffer from a chronic condition such as asthma or diabetes. Online GP services are perfect for prompt assessments, prescribing antivirals (if needed), managing mild to moderate symptoms, and identifying potential complications. They can also offer advice on home care, signs to watch for, and guidance on when to seek in-person medical treatment.What are bacterial infections?
Bacterial infections occur when harmful bacteria invade the body, multiply, and provoke an immune response. These infections can affect various parts of the body, including the skin, lungs, intestines, or bloodstream. Common instances include strep throat, urinary tract infections, pneumonia, and tuberculosis. In contrast to viruses, bacterial infections are typically treated with medication. However, it is important to recognise that not all bacteria are harmful; many coexist peacefully in the body and assist with processes like digestion. Bacterial infections can range from mild to severe, making early diagnosis and intervention crucial to prevent complications.Type of bacterial infections
The types of bacterial infections can differ based on their location within the body. Here are the main categories:- Respiratory infections: These target the lungs and airways. Typical examples include pneumonia, sinusitis, and bronchitis.
- Skin infections: These arise when bacteria enter through cuts or injuries. Examples include cellulitis, impetigo, and boils.
- Urinary tract infections (UTIs): Mostly caused by E. coli, A UTI affects the bladder, kidneys, or urethra.
- Gastrointestinal infections: These occur in the stomach and intestines, often leading to diarrhoea, cramps, or vomiting. Examples include Salmonella, E. coli, and Shigella.
- Sexually transmitted infections (STIs): Infections such as chlamydia, gonorrhoea, and syphilis belong to this category.
- Blood infections (sepsis): A serious condition where bacteria invade the bloodstream, often necessitating urgent medical attention.
- Nervous system infections: Bacteria can lead to meningitis by infecting the membranes surrounding the brain or spinal cord.
What causes bacterial infections?
Bacterial infections occur when harmful bacteria infiltrate the body, multiply, and elicit an immune response. These bacteria can enter via cuts, contaminated food or water, insect bites, or close contact with infected individuals. Poor hygiene, a weakened immune system, chronic diseases (like diabetes), or recent surgical procedures heighten the risk. Some bacteria are naturally found in the body but can lead to infections if they proliferate excessively or migrate to inappropriate areas.Bacterial infections symptoms
Symptoms of bacterial infections can vary based on their type and location, but common indicators include:- Fever and chills
- Tiredness or weakness
- Redness, swelling, or warmth (especially in skin infections)
- Pain in the infected area
- Pus or discharge
- Cough or shortness of breath (in respiratory infections)
- Frequent or painful urination (in UTIs)
- Digestive disturbances such as nausea, vomiting, or diarrhoea (in gastrointestinal infections)
Bacterial infections treatment options
Treatment options for bacterial infections vary according to the type and severity of the condition, but primary approaches include:- Medication: Most bacterial infections are managed with medicines, which kill or inhibit bacterial growth. The choice of antibiotic depends on the infection and the involved bacteria.
- Supportive care: This includes rest, hydration, pain relievers, and fever reducers to help alleviate symptoms while the body recovers.
- Hospitalisation: Severe infections such as sepsis or bacterial meningitis may require intravenous antibiotics, fluids, or oxygen in a hospital environment.
- Drainage or surgery: In cases like abscesses, surgical intervention may be necessary to drain pus or remove infected tissue.
- Probiotics: These may be suggested during or after antibiotic treatment to help restore healthy gut bacteria.
When to consult an online doctor?
You should seek an online consultation for a bacterial infection when you observe mild to moderate symptoms such as fever, fatigue, skin redness, painful urination, or a sore throat that fails to improve after a few days. Telehealth doctors can evaluate your situation, provide advice on at-home care, a prescription for your infection or approve request a test referral for infections. This service is also beneficial for obtaining quick guidance, prescription renewals, or get a medical certificate online, without needing to visit a clinic. However, if you encounter severe symptoms like a high fever, chest pain, confusion, or difficulty breathing, seek immediate medical attention in person.What are fungal infections?
Fungal infections are illnesses caused by the invasion and multiplication of fungi in or on the body. These infections can impact the skin, nails, mouth, lungs, or internal organs. Common infections include athlete’s foot, ringworm, thrush, and yeast infections. Although many fungal infections are mild and can be treated with creams or oral medications, some may become serious, particularly in individuals with compromised immune systems. Fungi flourish in warm, moist environments and can be transmitted through direct contact, contaminated surfaces, or disrupted body flora.How fungal infections occur?
Fungal infections occur when fungi penetrate the body via the skin, mouth, lungs, or genital areas, particularly in warm, moist settings. They can proliferate on the surface or more deeply within tissues if the immune system is compromised. Frequent causes encompass poor hygiene, excessive sweating, tight clothing, sharing personal items, or prolonged use of antibiotics (which disrupts natural microbial balance). Individuals with diabetes, compromised immunity, or certain health issues are at increased risk for fungal infections.Type of fungal infections
Various fungal infections exist based on their location and the fungi involved. Notable types include:- Superficial fungal infections – Impacts the skin, hair, and nails. Examples include athlete’s foot, ringworm, and nail fungus.
- Mucosal fungal infections – Affect moist regions like the mouth, throat, or genitals. Common examples include thrush and yeast infections.
- Subcutaneous fungal infections – Occurs beneath the skin due to fungi entering through cuts or wounds.
- Systemic fungal infections – Impact internal organs like the lungs or bloodstream. These are serious conditions and mainly affect individuals with weakened immune systems, such as candidiasis or histoplasmosis.
Fungal infections symptoms
Symptoms of fungal infections differ based on type and location, but generally include:- Itching, redness, and skin irritation
- Scaling, peeling, or cracking of the skin
- Rash or circular patches (as seen in ringworm)
- Thick, discoloured, or brittle nails
- White patches or discomfort in the mouth or throat (oral thrush)
- Pain, burning, or discharge in the genital areas (yeast infections)
- Fatigue, fever, or cough if the infection spreads internally
Fungal infections treatment options
Treatment options for fungal infections depend on the type and severity of the infection. Common treatments include:- Topical antifungal creams or ointments for skin and nail infections.
- Oral antifungal drugs are used for more serious or widespread infections.
- Medicated shampoos or powders for fungal infections of the scalp or body.
- Practising good hygiene and keeping affected areas dry to inhibit fungal growth.
- In severe cases, particularly with systemic infections, hospitalisation for intravenous antifungals may be required.
When to consult a doctor online?
You should reach out to an online doctor regarding fungal infections if you notice persistent or worsening symptoms despite using over-the-counter treatments. This includes intense itching, an expanding rash, changes in nails, pain, or infection signs like swelling and pus. Online consultations are valuable for obtaining an accurate diagnosis, prescription of antifungal medication, and management advice for symptoms. If you have a compromised immune system, diabetes, or other health conditions, it is especially vital to seek medical advice promptly. For severe symptoms such as fever or indications of deep tissue infections, immediate in-person care is essential.What are parasitic infections?
Parasitic infections arise when parasites, which are organisms that reside on or inside a host, invade the body and lead to illness. These parasites can either be single-celled organisms, such as protozoa, or multi-celled worms known as helminths. Such infections often occur via contaminated food, water, insect bites, or direct contact with infected individuals or animals. Common instances include malaria, giardiasis, and tapeworm infections. Depending on the type and severity, parasitic infections can impact various body parts and result in diverse symptoms.How parasitic infections infect humans?
Parasitic infections manifest when parasites penetrate the human body through multiple pathways. They can be transmitted by ingesting contaminated food or water, being bitten by insects (like mosquitoes), or having direct contact with infected soil, animals, or individuals. Some parasites may penetrate through the skin, whereas others can infiltrate the digestive system or the bloodstream. Risk factors for infection include poor hygiene, unsanitary living conditions, and travelling to regions with a high prevalence of parasites. Once inside the body, parasites reproduce and can induce symptoms by damaging tissues or initiating immune responses.Common types of parasitic infections
Common categories of parasitic infections are:- Protozoal infections – caused by single-celled parasites like Giardia (giardiasis), Plasmodium (malaria), and Entamoeba histolytica (amoebiasis). These typically affect the intestines or bloodstream.
- Helminth infections – caused by parasitic worms, such as roundworms, tapeworms, and flukes. Examples include ascariasis, schistosomiasis, and hookworm infections.
- Ectoparasitic infections – caused by parasites that live on the skin, such as lice, scabies mites, and ticks.
How are they contracted?
Parasitic infections can be acquired through several typical means. Eating contaminated food or drinking impure water can introduce parasites like Giardia or tapeworms into the digestive system. Mosquito or tick bites may transfer parasites responsible for malaria. Direct interaction with contaminated soil, water, animals, or infected individuals can also trigger infections, particularly with parasites like hookworms or scabies mites. Lacking hygiene, living in unsanitary conditions, and visiting regions where parasites are prevalent elevate the risk of infection. Some parasites can even enter through the skin or mucous membranes.Parasitic infections symptoms
Parasitic infections can lead to a broad array of symptoms depending on the parasite type and the affected area of the body. Typical symptoms include stomach discomfort, diarrhoea, nausea, and vomiting. Fatigue, weight loss, and weakness are also common indications. Certain infections may lead to itching, skin rashes, or visible worms in faeces. Others might cause fever, muscle soreness, and swelling. In severe cases, parasites can affect organs such as the liver, lungs, or brain, resulting in more severe issues. Symptoms may develop gradually or emerge suddenly following exposure.Parasitic infections treatment options
Parasitic infections are typically managed with specific antiparasitic medications that target the responsible parasite. These medications assist in eliminating or expelling the parasites from the body. Treatment options may include antiparasitic pills, creams, or injections, depending on the nature of the infection. In addition to medication, supportive care like hydration, proper nutrition, and symptom management is vital. In some instances, multiple treatments or follow-ups may be necessary to fully eradicate the infection. Avoiding contamination and practising good hygiene to prevent re-infection is equally important. For serious infections, hospitalisation or specialised care may be necessary.When to see a doctor online
Consulting a doctor online is advisable if you experience ongoing symptoms such as diarrhoea, abdominal discomfort, fever, or unexplained weight loss that could indicate a parasitic infection. If symptoms deteriorate, do not improve with home care, or if you notice blood in your stool, seeking medical guidance promptly is crucial. Online healthcare professionals can offer timely diagnoses, suggest diagnostic tests, and prescribe suitable treatment without the need to visit a clinic. Early consultation aids in preventing complications and accelerates recovery. If you have recently travelled to high-risk areas for parasites or have a compromised immune system, it is prudent to consult a doctor even for mild symptoms.Comparison of Viral, Bacterial, Fungal & Parasitic Infections
| Category | Viral | Bacterial | Fungal | Parasitic |
|---|---|---|---|---|
| Cause | Viruses via droplets, contact, food, water, insects. | Bacteria via cuts, food, water, insect bites, close contact. | Fungi in warm, moist areas via skin, mucosa, or disrupted flora. | Parasites via contaminated food, water, insect bites, or skin contact. |
| Common Examples | Cold, Flu, COVID-19, Hepatitis, HIV. | Strep throat, UTI, Pneumonia, TB. | Athlete’s foot, Ringworm, Thrush, Yeast infection. | Malaria, Giardiasis, Tapeworm, Scabies. |
| How It Spreads | Airborne droplets, contact, contaminated surfaces/food, water, insects. | Cuts, contaminated food/water, insect bites, direct contact. | Direct contact, contaminated surfaces, disrupted body flora. | Contaminated food/water, insect bites, soil, person-to-person contact. |
| Symptoms | Fever, cough, fatigue, rashes, body aches, nausea, swollen glands. | Fever, chills, swelling, pus, pain, fatigue, digestive issues. | Itching, redness, rash, thick nails, mouth patches, fatigue. | Diarrhoea, stomach pain, fatigue, weight loss, fever, skin rashes. |
| Treatment | Supportive care, antivirals, vaccines. | Medication, supportive care, hospitalisation, drainage, probiotics. | Topical/oral antifungals, hygiene, possible hospitalisation. | Antiparasitic medication, supportive care, hygiene, possible hospitalisation. |
| When to See a Doctor | Persistent fever, breathing issues, chest pain, worsening symptoms. | Persistent or worsening fever, pain, chest pain, confusion. | Persistent rash, intense itching, nail changes, fever, or systemic symptoms. | Ongoing diarrhoea, blood in stool, abdominal pain, fever, travel history. |
Conclusion:
In summary, viral, bacterial, fungal, and parasitic infections differ in origin and management, but all represent significant health threats. Recognising these infections helps in early detection, effective treatment, and improved prevention through hygiene, vaccination, and responsible medication use.FAQs
Are viral infections contagious?
Yes, most viral infections are contagious and can spread through touch, air, fluids, or insect bites.How long does a viral infection last?
Most viral infections last from a few days to two weeks. Mild illnesses like influenza or cold generally improve within 7 - 10 days, while others like HIV or hepatitis can result in chronic or lifelong infections.Are bacterial infections contagious?
Yes, bacterial infections can be contagious, but it depends on the type. Some spread through touch, air, or body fluids, such as strep throat or tuberculosis, while others, like urinary tract infection, usually don’t spread between people.Is influenza a bacterial or viral infection?
Influenza is a viral infection. It is caused by the influenza virus, not bacteria, and can be transmitted easily through droplets when an infected individual coughs, sneezes, or talks.Is thrush a fungal infection?
Yes, thrush is a fungal infection caused by an overgrowth of the yeast Candida—generally Candida albicans—in the mouth or throat.Are fungal infections contagious?
Yes, some fungal infections can be contagious. They are often transmitted through direct contact with the skin or by touching contaminated surfaces. Conditions like ringworm and athlete’s foot are common examples. However, not all fungal infections spread easily between people.Are parasitic infections common in Australia?
Parasitic infections are uncommon in most parts of Australia due to good sanitation and healthcare. However, they occur more frequently in certain remote indigenous areas and among travellers coming back from regions with higher infection levels. Public health efforts aim to reduce these cases through improving sanitation and education.Can children and the elderly use telehealth to get treatment for infections?
Yes, children and the elderly use telehealth to get treatment for infections. Telehealth enables them to communicate with healthcare providers remotely, which is especially helpful for those with limited mobility, living far from clinics, or needing prompt medical guidance. During virtual appointments, doctors can evaluate symptoms, recommend tests or treatments, and prescribe medications. However, if the illness is serious or requires physical examination, in-person care may still be necessary.See a GP online within just 15 minutes.
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Disclaimer
This blog is for general informational purposes only and does not indicate that Hola Health provides all treatments or preventive measures mentioned. It is not intended to be a substitute for professional medical advice. Always seek the guidance of your doctor or other qualified health professional with any questions you may have regarding your health or a medical condition. For emergencies please immediately contact 000. Any medical topics discussed are intended to educate, not to imply availability through Hola Health.