“I have a fever, but it doesn’t feel like a typical cold.” “My child keeps vomiting and has diarrhea.” “Blistery rashes have appeared on my back.” — Symptoms like these may be caused by an infectious disease other than a cold or influenza.
There are many types of infectious diseases, each with different causative microorganisms, routes of transmission, and treatment approaches. Getting an accurate diagnosis is the quickest path to recovery. Keldsen Family Clinic is a family-oriented clinic offering both Psychosomatic Medicine and Internal Medicine, a 1-minute walk from ‘Oizumi Yubinkyoku’ bus stop, accessible by Seibu Bus from Oizumi-Gakuen Station. We are open on weekends, holidays, and during the year-end and New Year period, so we can see you promptly even when an infection strikes on a day off. Telemedicine is also available — please feel free to reach out. For information about colds and influenza specifically, please see our separate page (Colds & Influenza).
The Basics of Infectious Diseases
An infectious disease is a general term for illnesses caused when microorganisms such as bacteria, viruses, fungi (molds), or parasites enter the body and multiply. These are conditions that anyone can develop in the course of daily life, and they affect people of all ages — from children to older adults.
Understanding the difference between “bacteria” and “viruses” is key to understanding infectious diseases.
Bacteria are single-celled microorganisms that can reproduce on their own. Representative examples include streptococcus, mycoplasma, and E. coli. Antibiotics are effective against bacterial infections, and with appropriate use, improvement can generally be expected.
Viruses cannot reproduce on their own — they must enter human cells to multiply. Examples include norovirus, RS virus, and varicella-zoster virus. For most viral infections, treatment centers on symptomatic care (relieving symptoms). However, antiviral medications are effective against certain viral infections, and early administration may yield benefits in conditions such as shingles and COVID-19.
Understanding routes of transmission also helps make sense of how symptoms spread.
- Droplet transmission: Inhaling droplets expelled by coughing or sneezing (streptococcus, mycoplasma, COVID-19, etc.)
- Contact transmission: Touching the skin or belongings of an infected person and then touching your mouth or nose (norovirus, RS virus, etc.)
- Oral transmission: Consuming contaminated food or water (norovirus, rotavirus, etc.)
Knowing the route of transmission leads to appropriate preventive measures.
Common Types of Infectious Diseases and Their Features
Beyond colds and influenza, a wide variety of infectious diseases are commonly encountered in daily clinical practice. Organizing them by the area and nature of symptoms yields the following categories.
Upper respiratory infections (throat and airway infections)
- Streptococcal pharyngitis: A bacterial infection caused by group A beta-hemolytic streptococcus. Characterized by high fever, severe sore throat, and a red, bumpy tongue (strawberry tongue). Antibiotic treatment is effective; without proper treatment, complications such as rheumatic fever or nephritis may develop
- Acute pharyngitis and tonsillitis: Can be caused by either viruses or bacteria. Symptoms include sore throat, fever, and difficulty swallowing
- Mycoplasma pneumonia: A type of pneumonia caused by the bacterium mycoplasma. Characterized by a prolonged dry cough and fever. Because mycoplasma lacks a cell wall, penicillin-type and cephalosporin-type (beta-lactam) antibiotics are ineffective. Macrolide antibiotics are the first-line treatment, though macrolide-resistant strains have been increasing in recent years; in such cases, tetracyclines or fluoroquinolones may be used as determined by the physician based on the patient’s age and condition. More common in children and younger adults
Gastrointestinal infections (digestive system infections)
- Infectious gastroenteritis (norovirus): Causes sudden vomiting, diarrhea, and abdominal pain. Predominantly occurs in winter; because even a very small amount of virus can cause infection, secondary transmission within households is common
- Infectious gastroenteritis (rotavirus): A viral gastroenteritis most commonly seen in infants and young children. Characterized by whitish, watery diarrhea; dehydration requires careful attention. Vaccination has made it easier to prevent severe illness
Respiratory infections
- RS virus infection: A viral infection requiring particular attention in infants, young children, and older adults. Begins with a runny nose and fever; in infants, it may progress to bronchiolitis. In adults, the illness is usually mild
- COVID-19: With recent circulating strains, the main symptoms tend to include severe sore throat, fever, and fatigue. Antiviral medications may be indicated for patients at higher risk of severe illness
Skin and nerve infections
- Shingles (herpes zoster): Occurs when the varicella-zoster virus (the same virus that causes chickenpox), which remains dormant in the body, reactivates during periods of weakened immunity. Characterized by tingling pain and blisters that appear along one side of the body. Early administration of antiviral medication is effective. Vaccination can help reduce the risk of developing shingles
Urinary tract infections
- Urinary tract infections (cystitis and pyelonephritis): Occur when bacteria travel from the urethra into the bladder or kidneys. Main symptoms include pain during urination, frequent urination, a sense of incomplete emptying, and fever. More common in women; antibiotic treatment is the standard approach. In pyelonephritis, high fever and lower back pain may also be present
Characteristics and Symptoms of Infectious Diseases
The symptoms of infectious diseases vary widely depending on the causative microorganism and the site of infection. Organizing “where and what kind of symptoms are occurring” helps guide an accurate diagnosis.
Specific Symptom Examples
Systemic symptoms
- Fever (ranging from low-grade to high fever)
- Severe fatigue and malaise
- Chills and shivering
- Loss of appetite and weight loss
- Swollen lymph nodes
Throat and respiratory symptoms
- Severe sore throat and difficulty swallowing
- Prolonged dry cough (commonly associated with mycoplasma)
- Shortness of breath and abnormal breathing sounds
- Hoarseness and phlegm
Digestive symptoms
- Sudden vomiting and repeated diarrhea
- Abdominal pain and discomfort
- Whitish, watery diarrhea (commonly associated with rotavirus)
- Signs of dehydration (dry mouth, decreased urine output, dizziness)
Skin and nerve symptoms
- Severe pain or burning sensation along one side of the body (shingles)
- Red rashes and blisters (shingles, streptococcal skin infections, etc.)
- Strawberry tongue and redness inside the mouth (streptococcus)
Urinary symptoms
- Pain or stinging during urination
- Frequent urination and a sense of incomplete emptying
- Lower back pain and high fever (when progressing to pyelonephritis)
Seek medical attention promptly if you experience the following
- High fever lasting more than 3 days
- Difficulty breathing or rapid breathing
- Suspected dehydration from vomiting or diarrhea (unable to take fluids or no urine output)
- Severe pain and a rash on one side of the body
- Infection symptoms in older adults, infants, pregnant individuals, or immunocompromised individuals
Treatment and Management of Infectious Diseases
Treatment strategies for infectious diseases vary significantly based on whether the cause is bacterial or viral, the severity of symptoms, and the patient’s age and underlying health conditions. The basic approach is to “first identify the type of infection and then provide the appropriate treatment.”
At Keldsen Family Clinic, we carefully assess your symptoms and clinical course, combine testing as needed, and recommend the most appropriate treatment plan. For severe cases or those requiring hospitalization, we coordinate with specialized medical institutions for ongoing support.
Medication Therapy
Medications for infectious diseases are selected based on the causative agent.
Antibiotics (effective against bacterial infections)
- Penicillin-type and cephalosporin-type: Used for streptococcal pharyngitis, tonsillitis, cystitis, and other conditions
- Macrolide-type: Effective against mycoplasma pneumonia and certain skin infections. Can also address bacteria that are unresponsive to penicillin-type antibiotics
- Fluoroquinolone-type: Commonly used for urinary tract infections and respiratory infections
Antibiotics are not effective against viral infections. Using them “just in case” can lead to side effects and contribute to antibiotic resistance, so it is important to use them only as directed by a physician.
Antiviral medications (effective against certain viral infections)
- Shingles: Antiviral medications such as aciclovir and valaciclovir, administered early (ideally within 72 hours of the rash appearing), may help reduce symptoms and lower the risk of post-herpetic neuralgia
- COVID-19: Antiviral medications may be an option for patients at higher risk of severe illness (prescribed at the physician’s discretion)
Symptomatic relief medications
Antipyretics, probiotics, antiemetics, fluid replacement (for dehydration management), and other medications are used to ease uncomfortable symptoms while supporting the body’s natural recovery.
Psychosocial Support
When you have an infectious disease, worries such as “How will this affect my work or school?” and “What if I spread it to my family?” can weigh heavily. For those who need to isolate, feelings of loneliness and stress are not uncommon.
Keldsen Family Clinic has both Psychosomatic Medicine and Internal Medicine departments, allowing us to address anxiety and emotional distress alongside physical treatment. Even if your symptoms are mild but your mood has been low, please do not hesitate to talk with us.
Considerations for School and Work
Certain infectious diseases have established guidelines for school attendance suspension and home rest.
- Streptococcal pharyngitis: Once appropriate antibiotics have been started for at least 24 hours, the fever has subsided, and overall condition has improved, return to school or daycare may be considered under a physician’s guidance
- Norovirus and rotavirus: Rest at home until vomiting and diarrhea have resolved. Proper handling of stool and vomit is also important for preventing further spread
- Shingles: Shingles in adults is not subject to mandatory school attendance suspension under the School Health and Safety Act in Japan; however, if there is a possibility that the rash may come into contact with others, it is advisable to coordinate with your school or workplace in consultation with your physician
- COVID-19: Refrain from going out for a specified period after symptom onset, with return to activities approximately 24 hours after symptoms have improved (follow the latest public health guidelines)
We can also issue medical certificates or documentation when needed for your workplace or school.
Home Management
Many infectious diseases spread easily within the household, so it is important for the entire family — not just the patient — to take preventive measures.
- Thorough handwashing: Use soap and running water for at least 30 seconds. Always wash after returning home, before cooking, before meals, and after using the restroom
- Avoid sharing towels and dishes: Use separate items during the infectious period
- Handling vomit and stool: Viruses such as norovirus remain infectious even after drying, so wear disposable gloves and a mask when handling these. Disinfect vomit and stool with sodium hypochlorite solution (approximately 1,000 ppm chlorine concentration), then wipe with water. For routine surface cleaning, approximately 200 ppm is the standard (dilute according to product label instructions)
- Separate the patient’s room: Isolate to the extent possible and ensure regular ventilation
- Support with hydration: Actively provide fluids and electrolytes to infants, young children, and older adults who are particularly prone to dehydration
Extra caution is warranted when infants, young children, older adults, pregnant individuals, or family members with chronic conditions are in the household.
General Lifestyle Self-Care
Building healthy daily habits is essential for preventing infections and recovering quickly when you do get sick.
Vaccination
Keldsen Family Clinic offers a wide range of vaccinations, including influenza, COVID-19, shingles, rotavirus, hepatitis B, and pneumococcal vaccines. Because the right vaccines for you depend on your age, living environment, and underlying conditions, we recommend selecting them in consultation with your physician.
Basic infection prevention
- Make handwashing a habit after going outside, before cooking, and at other key times
- Wear a mask in crowded places during peak seasons
- Ventilate indoor spaces regularly; during dry seasons, use a humidifier to maintain appropriate moisture levels
- Handle raw foods carefully and cook food thoroughly
Habits that help maintain immune function
- Adequate sleep (aim for 7 to 8 hours)
- A balanced diet (with attention to protein, vitamins, and minerals)
- Regular moderate exercise to maintain physical fitness and immune function
- Avoid excessive stress and do not let fatigue build up
Early consultation and prompt action are key to preventing infectious diseases from becoming severe. If you feel that “this doesn’t seem like a regular cold,” “my symptoms are dragging on,” or “I’m worried about spreading it to my family,” please reach out to Keldsen Family Clinic. Seibu Bus from Oizumi-Gakuen Station, 1-min walk from ‘Oizumi Yubinkyoku’ bus stop, open on weekends, holidays, and during the year-end and New Year period, with telemedicine also available.