Most colds do not cause complications beyond minor inconveniences, such as missed days at school or work. Flu, however, can pose more serious complications, though most people recover within a week or two without problems.
Adults who have a cold sometimes develop bacterial co-infections, such as pneumonia, ear infections, sore throats and sinusitis (inflammation of the sinuses). Up to 2 percent of colds become sinusitis. Sinusitis is usually diagnosed based on the duration of symptoms. The key factor regarding sinusitis is how long the sinuses have been congested, allowing time for the bacteria to grow in the mucus. Additional symptoms are discolored mucus (green or brown, possibly bloody), a metallic taste in the mouth, loss of smell and taste, upper-teeth pain if the maxillary sinuses are involved, face pain and fever.
Most children with colds do not develop complications. If a child develops a fever after the third day of a cold, the child should see a doctor as it could be an infection in the ear or lungs. Up to 19 percent of children with a cold will develop either a bacterial or viral ear infection. If a child has a cough or any trouble breathing, pneumonia is a possibility. Children with asthma may wheeze more with a cold, although children without asthma may also wheeze with a cold. Lastly, if nasal congestion is not getting better after 10 days, the child may have a new cold virus, or sinusitis may be a consideration.
For the flu, complications can be more severe and the patient may need hospitalization. According to the World Health Organization, there are about 3 to 5 million cases of severe illness and about 250,000 to 500,000 deaths related to influenza per year.
Higher-risk patients tend to get experience greater complications. Higher-risk patients include people with any of the following:
• Asthma and other lung diseases
• Diabetes and obesity
• Heart disease, congestive heart failure and kidney and liver problems
• Certain blood disorders, such as leukemia and sickle cell disease
• People younger than 19 years of age on long-term aspirin therapy
• Weakened immune system due to disease or medication, such as cancer or HIV medications, or on chronic steroids or other immunosuppressive drugs
• Adults 65 years and older and kids younger than 5, but especially younger than 2 years of age
• Pregnant women and women up to two weeks after the end of pregnancy
• American Indians and Alaska Natives
Complications can range from viral pneumonia, bronchitis and bacterial pneumonia (which are the most common complications) to exacerbating preexisting heart and lung problems. In very rare cases, cold and flu complications can lead to diseases of the brain such as Guillain-Barré syndrome, transverse myelitis and Reye’s syndrome as well as inflammation of the membrane that surrounds the heart (pericarditis).
Not only do colds and flu cost money to treat, with doctor’s visits and medications, they are a burden to the economy of the country due to lost days from work. In the U.S., about 75 to 100 million people see their doctors with such symptoms per year, and about 150 million days are missed from work.