Cold vs Flu: Symptoms, Differences, Treatment and When to See a Doctor

Colds and flu both affect the nose, throat and lungs and can feel similar at first. But influenza (flu) is generally more severe and can cause serious complications, whereas colds are mild. Knowing the difference helps you decide how to care for yourself and when to get help. Many other illnesses, including dengue and COVID-19, also start with fever and aches, which is why a fever in Sri Lanka should never be assumed to be "just flu".

Cold vs flu at a glance

• Onset: cold is gradual over 1-2 days; flu is sudden, over hours.
• Fever: cold, rare or low-grade; flu, common, often 38-40 °C for 3-4 days.
• Aches and pains: cold, slight; flu, usual and often severe.
• Tiredness and weakness: cold, mild; flu, can be extreme and last 2-3 weeks.
• Headache: cold, uncommon; flu, common.
• Runny or stuffy nose and sneezing: cold, very common; flu, sometimes.
• Sore throat: cold, common; flu, sometimes.
• Cough: cold, mild to moderate; flu, often dry and can be intense.
• Chills: cold, uncommon; flu, common.
• Complications: cold, sinus or ear infection occasionally; flu, pneumonia, worsening of asthma, heart or diabetes problems, and hospitalisation.

Causes and spread

Colds are caused by more than 200 viruses, most commonly rhinoviruses. Flu is caused by influenza A and B viruses, which change each year. Both spread through droplets from coughs and sneezes, contaminated hands and surfaces. In tropical countries like Sri Lanka, influenza occurs through the year, often with peaks during the rainy seasons.

Home treatment for both

There is no cure for a cold, and antibiotics do not work against viruses. Treatment aims to ease symptoms:

• Rest and stay at home, to recover and prevent spreading illness.
• Drink plenty of fluids: water, soups, herbal tea, king coconut water, ORS if you have sweating or poor appetite.
• Paracetamol for fever and aches. Use ibuprofen only if your doctor agrees and you are certain it is not dengue. Do not give aspirin to children or teenagers. For children, use our paracetamol dose calculator and see cough and cold in children.
• Saline nasal spray or drops for a blocked nose, and steam from a warm shower.
• Throat comfort: warm salt-water gargles, lozenges for adults and older children, honey and lime in warm water (not for babies under 1 year).
• Cough: honey helps for older children and adults. Avoid cough syrups in children under 6.
• Decongestants and antihistamine combinations may help adults for a few days, but avoid them if you have high blood pressure, heart disease or glaucoma without medical advice.
• Avoid smoking and smoke exposure.
• Wash hands often and cover coughs.

Antiviral treatment for flu

Antiviral medicines such as oseltamivir can shorten flu by about a day and reduce complications if started within 48 hours of symptoms. Doctors prescribe them mainly to people at higher risk of complications:

• Adults over 65 and young children, especially under 2
• Pregnant women and those up to 2 weeks after delivery
• People with asthma, chronic lung, heart, kidney, liver or neurological disease
• People with diabetes or weakened immunity
• Severe or worsening illness

Ask for a test or doctor review early if you are in a high-risk group.

Is it dengue, COVID-19 or leptospirosis?

Fever with aches in Sri Lanka can be dengue, leptospirosis or other infections. Flu usually comes with cough and nasal symptoms. Dengue typically does not cause a runny nose, but often brings pain behind the eyes, rash and later warning signs. See dengue warning signs and leptospirosis. Do not take aspirin or ibuprofen for fever if dengue is possible. COVID-19 can mimic both, so test if you can.

When to see a doctor urgently

Seek medical care or go to hospital for:

• Difficulty breathing, fast breathing, chest pain or pressure
• Blue lips or face
• Persistent fever above 39 °C or fever lasting more than 3-4 days
• Confusion, severe drowsiness, stiff neck or seizures
• Severe or persistent vomiting, or signs of dehydration
• Symptoms that improve then return with a worse fever or cough (possible pneumonia)
• Worsening of a chronic condition such as asthma, diabetes or heart failure
• In babies: fever under 3 months, poor feeding, fast breathing, or limpness

Prevention

• Annual flu vaccine for high-risk groups, since viruses change each year. Ask your doctor about availability and timing.
• Hand-washing with soap for 20 seconds, and avoid touching your face.
• Cough etiquette: cover with a tissue or elbow, and dispose of tissues.
• Stay away from others when sick, and wear a mask in crowded or indoor places when ill.
• Ventilate rooms and clean frequently touched surfaces.
• Healthy lifestyle: sleep, balanced diet, exercise and no smoking.
• Vitamin C, zinc and herbal supplements have little proven benefit for preventing colds.

Return to normal activities

You can generally return to work or school when the fever has gone for 24 hours without medicine and you feel well enough. A mild cough can persist for weeks.

References

• World Health Organization: influenza (seasonal) fact sheet
• Centers for Disease Control and Prevention: flu symptoms and treatment guidance
• NICE: common cold and influenza management guidance
• Sri Lanka Ministry of Health, Epidemiology Unit: influenza surveillance