Infectious Diseases: Flu, Colds, UTI, Herpes and Others
Infections are the most common reason people see a doctor. Most resolve on their own and do not require antibiotics. But some are dangerous and need prompt treatment. The main challenge is not confusing the two. This article covers the most common infections — how to recognize them and when to seek medical care.
Flu or Cold: How to Tell in 2 Minutes
"I have the flu" — most people say this with any common cold. In reality, true influenza is a distinct illness caused by the influenza virus, and it is significantly more severe than most respiratory infections.
Common cold (URTI): gradual onset. Main symptoms — runny nose, nasal congestion, sore or scratchy throat, mild malaise. Fever is low or absent. Cough may develop later. The person is usually functional — able to work, if with some difficulty.
Flu (influenza): sudden onset — people often name the exact hour they "suddenly felt terrible." Temperature rises quickly, often to 39–40°C. Severe headache, pain in the eyes when moving them, aching throughout the body — especially in muscles and joints. A runny nose may occur but is secondary. Profound weakness — hard to get out of bed. Cough is dry and painful.
Why it matters: flu is dangerous due to complications — pneumonia, myocarditis, neurological injury. It is particularly severe in older adults, those with chronic conditions, pregnant women, and children under 5. For these groups, timely antiviral treatment (oseltamivir) and vaccination are critically important.
For both colds and flu: rest, plenty of fluids, fever reduction as needed (paracetamol, ibuprofen). Antibiotics do not work for viral infections — they kill bacteria, not viruses.
UTI: Symptoms and When Antibiotics Are Needed
A urinary tract infection (UTI) — inflammation of the bladder — is one of the most common infections in women. About half of all women have at least one UTI in their lifetime.
Classic symptoms: frequent and painful urge to urinate (every 10–20 minutes), sharp pain or burning during urination, a feeling of incomplete bladder emptying, cloudy or dark urine, sometimes with an odor. Blood in the urine can occur with UTIs — this is called hemorrhagic cystitis.
In most cases, UTIs are caused by E. coli and require antibiotics. Treating a UTI with herbal remedies or just drinking plenty of fluids may be tried only in very mild cases — and with caution.
When a UTI needs urgent care: back pain develops, especially on the sides of the spine — this signals the infection has spread to the kidneys (pyelonephritis). Fever above 38°C, chills, nausea combined with UTI symptoms — this requires immediate consultation. Pyelonephritis is treated more aggressively and sometimes requires hospitalization.
Recurrent UTIs (more than 2–3 episodes per year) are a reason to see a urologist or gynecologist. Sometimes the cause is incomplete treatment of a previous episode, anatomical factors, or other underlying conditions.
Herpes: Types and When to Treat
The herpes virus is among the most widespread on earth. An estimated 80% or more of people carry herpes simplex virus type 1. Most don't know it — the virus can "sleep" in nerve ganglia for years without any symptoms.
Herpes type 1 (oral herpes, "cold sore"): painful blisters on or around the lips. Triggered by stress, cold, UV exposure, immune suppression, or another infection (hence the name "cold sore"). Resolves on its own in 7–14 days. With frequent recurrences, antiviral medications (acyclovir, valacyclovir) speed healing and reduce outbreak frequency.
Herpes type 2 (genital herpes): blisters and sores in the genital area. Transmitted sexually. The first episode is the most painful and may be accompanied by fever. Subsequent episodes are usually milder. The virus remains in the body for life, but antiviral therapy controls the frequency and severity of outbreaks. With frequent episodes — suppressive therapy (continuous antiviral use).
Shingles (varicella-zoster virus): in people who have had chickenpox, the virus "sleeps" in nerve ganglia and may reactivate with age or immune suppression. It presents as pain and a rash along a nerve — typically on one side of the trunk. The characteristic pain often precedes the rash by 2–3 days. Antivirals for shingles should be started as early as possible — ideally within the first 72 hours.
Pneumonia: Signs You Cannot Miss
Pneumonia is inflammation of lung tissue. It is not simply "a bad bronchitis" — pneumonia can be life-threatening, particularly in older adults, young children, and those with weakened immune systems.
Symptoms of pneumonia: high fever (38–40°C), cough — initially dry, then producing sputum (sometimes rust-colored or yellow-green), shortness of breath, chest pain with breathing or coughing. Marked weakness and sweating. In older adults, pneumonia can present without high fever, with confusion and shortness of breath being more prominent.
Pneumonia requires confirmation by chest X-ray. Treatment depends on the type (bacterial, viral, fungal) and severity — from oral antibiotics at home to intensive care.
When to call emergency services: shortness of breath at rest, breathing rate above 30 per minute, blood pressure below normal, confusion, or blue discoloration of the lips. These are signs of severe pneumonia.
Getting Sick Often — What Does It Mean?
Getting 4–6 respiratory infections per year as an adult is normal, especially with children or a people-facing job. The immune system trains itself through exposure.
When to investigate: if colds are prolonged (more than 10–14 days), unusually severe, quickly complicated (sinusitis, bronchitis, pneumonia), or if a person gets sick more than 8–10 times per year — it's worth finding the cause.
Possible reasons for reduced immune function: chronic stress and poor sleep, vitamin D, iron, or zinc deficiency, diabetes, HIV infection, immunosuppressive medications, cancer treatment, or chronic lung or kidney disease.
Supplements "for immunity" without identifying the actual cause are a poor investment. Start with a basic workup: full blood count, vitamin D, ferritin, blood glucose.
Not sure who to see for recurring infections? Check your symptoms or use the doctor-matching tool.
Frequently Asked Questions
Do I need antibiotics if my temperature is 39°C?
High fever is not an indication for antibiotics. It shows your immune system is fighting the infection. Antibiotics are only needed for bacterial infections. Most respiratory infections and flu are viral — antibiotics won't help and can cause harm.
Can a UTI be treated without antibiotics?
Very mild episodes sometimes resolve on their own. But in most cases, without antibiotics the infection can spread to the kidneys. The decision is made by a doctor — after a urinalysis.
Is a cold sore contagious?
Yes. The virus is active during the blister phase and for a few days after healing. Avoid kissing and sharing utensils during this period. Asymptomatic viral shedding can also transmit the virus, though less frequently.
Do I need a flu shot every year?
Yes. The influenza virus mutates, so the vaccine is updated annually. Vaccination reduces the risk of severe illness and complications. It is especially important for older adults, pregnant women, those with chronic conditions, and healthcare workers.
How do I know if a cold has turned into sinusitis?
Signs of sinusitis: pain and pressure in the forehead, cheeks, or around the eyes (especially when bending forward), nasal congestion not improving after 10 days, green or yellow nasal discharge, and sometimes fever. Acute sinusitis is most often bacterial and may require antibiotics.
Symptomatica is an informational reference service. Not a medical service; does not diagnose or prescribe treatment. For any symptoms, please consult a doctor.