Ask the doctors: Knowing the difference between a cold and the flu

Dear Doctors: My husband and I both work in an office, and our three kids are in school. That's a lot of exposure to germs and bugs. When someone gets sick, how do you know if it's a cold or the flu — or worse? Do you always need to see a doctor?

Dear Reader: A variety of viruses, bacteria and even fungi can cause respiratory tract infections. Because they affect the same tissues, they often produce similar symptoms. That can make it difficult to know which illness someone has contracted.

The most common respiratory infections here in the United States are two that you're asking about, namely the flu, or influenza, and the common cold. Other possibilities include COVID-19, pneumonia and bronchitis. Unlike during the height of the pandemic, the flu is outpacing COVID-19 this year. Pneumonia, another possible respiratory infection, is not as common as the flu or a cold. (We are addressing COVID-19 and pneumonia in upcoming columns. Our recent column about bronchitis can be found in the archives.)

The common cold is caused by a virus, usually rhinovirus and sometimes coronavirus. An identifying characteristic of a plain old cold is that the symptoms it causes occur from the neck up. These include a sore throat, clogged sinuses, a runny nose, sneezing, the production of thick (and seemingly endless) mucus, ear congestion, watery eyes and sometimes a headache. Mild chest congestion and a mild fever are possible, but do not always occur.

Having a cold can be miserable, but it rarely needs medical intervention. One notable exception is if it generates an ear infection. This can occur if bacteria begin to grow in fluid that has built up in the middle ear. Symptoms of an ear infection include pain, muffled hearing, visible discharge and dizziness. If symptoms persist or become severe, it can become necessary to see a doctor for antibiotics to clear up the infection.

That brings us to the flu, which is caused by the influenza virus. Unlike a cold, which typically has a gradual onset, the flu hits hard and fast. Symptoms can be similar to those of the common cold, but are markedly more intense. People with the flu often have a high fever; chills, exhaustion and widespread body aches are common. The infection can also affect the respiratory tract, causing a persistent cough and mucus production.

For both a cold and the flu, recovery begins with rest and supportive care. The symptoms are caused by your immune system's fight against the viral invaders, so you want to help it along. That means drinking plenty of fluids, eating a healthy diet and -- yes, we're repeating ourselves here -- getting plenty of rest. Over-the-counter medications to address fever, cough, sore throat and congestion can be helpful. Most people will begin to recover in three to five days. For those with influenza, the antiviral medication Tamiflu is an option.

Many people ride out these illnesses at home. But if symptoms become severe, consider an office visit with your doctor for evaluation, diagnosis and further treatment.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.