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The flu and the common cold are both respiratory illnesses. Common cold is acute viral infection of the upper respiratory tract.

The resulting inflammation involves the nasal passages, throat, sinuses, trachea, and bronchi. The common cold can be caused by one of many viruses. Colds usually do not result in serious health problems, such as pneumonia, bacterial infections, or hospitalizations. About half of all cases of common cold are caused by the rhinovirus group. Usually people call a severe common cold the flu, but they are quite different illnesses.  The flu and the common cold are caused by different viruses. Flu is an acute viral respiratory disease with clinical manifestations that often resemble a severe form of the common cold. Symptoms of flu usually start suddenly with a high fever and you may feel sick enough to go to bed.  All age groups are susceptible, but the prevalence is highest in school-age children. 

What is difference between cold and flu?

The flu is worse than the common cold.  Symptoms such as body aches, fever, headache, chills, extreme tiredness, and dry cough are severe. If you have common cold you are more likely to have a runny or stuffy nose. It is very difficult to tell the difference between common cold and flu. The flu causes the whole body ache. With the flu, you are sick all over your body.  The common cold usually affects the nose and throat only. The three most common symptoms of a cold are nasal stuffiness, sneezing, and runny nose. If you have common cold you should know that throat irritation is often involved, but not with a red throat. You should know that if you have flu is more likely that you have higher fever than if you have common cold. The flu begins abruptly, with a fever in the 102 to 106 degree range.  With flu you will probably have significant lack of energy. If you have flu you may have other systemic symptoms such as dizziness or vomiting. If you have flu you will probably have a sore red throat and a headache.

Disease process of common cold

The pathogenesis of colds is still sketchy. The virus is deposited in the nasopharynx, where it moves to the adenoids and a rich bed of viral receptors. An inflammatory reaction is evoked, resulting in vasodilation, mucus production, coughing, and sneezing about 16 hours after initial infection. Within one to three days, the nasal secretions usually become thicker and yellow or green.  This is a normal part of the common cold and not a reason for antibiotics. The virus spreads to the ciliated epithelial cells in the nasal passages, and symptoms continue for 4 to 10 days. The virus is active for about 3 weeks and may affect the trachea and bronchi, particularly in individuals with chronic respiratory disease. 

Disease Process of flu

After a 48-hour incubation period, the virus penetrates the surface of the upper respiratory tract mucosa, destroying the ciliated epithelium and reducing the viscosity of mucosal secretions. This facilitates the spread of virus-laden exudates to the lower respiratory tract, with resultant necrosis and desquamation of the bronchi and alveoli. The virus of flu affect the respiratory tract, and produce symptoms of a cold, croup, sore throat, bronchiolitis, ear infection, and/or pneumonia.  Between day 2 and day 4 of the infection, the whole body (aches) symptoms begin to subside, and respiratory symptoms begin to increase. The disease is generally self-limiting, with acute symptoms lasting 2 to 7 days and lingering symptoms lasting another week.

Symptoms of cold

The symptoms we have during a viral illness are often the body's attempt to get rid of the virus. Typical symptoms of common cold include nasal congestion and discharge, sore throat, sneezing, coughing, headache, and fatigue. Febrile reactions occur in infants and young children but are uncommon in older children and adults.

Symptoms of flu

The onset of influenza types A and B is sudden, marked by chills, fever, generalized aches and pains, headache, and photophobia. Respiratory symptoms begin with a scratchy, sore throat; substernal burning; and nonproductive cough. Later cough becomes severe and productive, and weakness, fatigue, and sweating persist. Influenza C produces milder symptoms.

Causes of flu and common cold

Spring and summer colds are often caused by picornaviruses, whereas fall colds are frequently caused by parainfluenza and winter colds by coronavirus strains. The mechanisms of spread are not clearly defined and may vary somewhat by viral type. Direct contact is implicated in rhinovirus colds; airborne infection by droplet is probably the mechanism in other viral strains.

Flu is caused by orthomyxovirus types A, B, and C, which are spread by direct person-to-person contact or by airborne droplet spray. Flu generally occurs in the late fall and early winter and can reach epidemic proportions when a modified form of the virus emerges for which the population has no immunity.

Complications of flu and common cold

The most common complications of common cold are the secondary overlay of a bacterial infection with purulent sinusitis or otitis media and the triggering of bronchospasms in persons with asthma.
The most common complication of flu is viral pneumonia or a secondary bacterial pneumonia. Individuals who have a compromised respiratory system and the elderly are most susceptible.

Diagnosis of flu and common cold

The diagnosis of common cold is made by clinical examination, while ruling out secondary bacterial sinusitis, otitis media, and streptococcal pharyngitis. Flu can be diagnosed if tissue culture of nasal secretions or fluorescent antibody staining of secretions is positive for virus.

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Treatments for common cold are medications. Usually acetaminophen analgesics if you have headache.  Nasal sprays are important for decongestion. Your doctor probably will recommend you saline gargle or topical anesthetics for sore throat. If you have common cold you shouldn’t use antibiotics. You should know that antibiotics won’t help a common cold or flu. Antibiotics are used to treat infections caused by bacteria and do not have any effect on viruses such as colds and flu. Using antibiotics when you don't need them may make them less effective when you do need them.  If your child has common colds you shouldn’t give him or her Aspirin. Rest for comfort and to minimize spread of common cold.  Good handwashing and careful handling of items in the environment are important to minimize viral contact by others. You should intake enough fluids for hydration. Drinking plenty of fluids is essential to prevent dehydration.
Treatment of flu usually includes some medications. Analgesics are given for headache, aches, pains.  Nasal sprays for congestion.   Antitussives are given for cough. Flu vaccine is important for prevention if zou have high risk, or you are older and chronic ill. Amantadine can also be used for prevention of or early intervention for influenza type A in high-risk groups. Consult your doctor for an annual flu injection. The vaccination dramatically lessens the severity of the flu, but has no effect on the common cold. Adequate hydration, rest, careful handling of items in the environment and good handwashing to reduce the spread of the virus is most important.

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