Cold and flu are both viruses, neither treated with antibiotics
Q: What's the difference between a cold and the flu, and how do you know which one you've got? Why can't antibiotics help?
A: Whether it's a cold or the flu, the reason you are feeling awful is because you've been infected by a virus. More than 200 different types of viruses can cause a cold, and the most common is the rhinovirus, the culprit behind up to half of all colds. The flu, as its name suggests, is caused by the influenza virus. Of the four known types of influenza virus, labeled A, B, C and D, the seasonal epidemics we prepare for each winter are caused by influenzas A or B.
When the immune system senses that a cold or flu virus has entered the body, it goes to war. This includes using every weapon at its disposal to attack and destroy the intruders. Unfortunately, this causes the physical symptoms that make having a cold or the flu so miserable. These include sore throat, runny nose, chest congestion, coughing, sneezing, fever, headache, body aches and fatigue. Some people may also experience diarrhea or vomiting.
The symptoms of a cold and the flu are often similar, but the potential outcomes are different. A cold is a milder illness that rarely leads to serious health problems. The flu, by contrast, is more severe than a cold. It can also lead to serious complications, some of them life-threatening. These include viral or bacterial pneumonia, inflammation of the heart or the brain, and sepsis, a response to infection that is so extreme, it can lead to death. The flu can also worsen chronic medical conditions, such as asthma, diabetes and heart disease.
The only reliable way to differentiate between a cold and the flu is with a special test performed on cells and fluids swiped from the inside of the nose or the back of the throat. Two quick tests can be performed in the doctor's office. These are the rapid influenza diagnostic test, or RIDT, which detects proteins associated with the influenza virus, and the rapid molecular assay, which identifies viral genetic material. Each test takes about 15 minutes, but neither is infallible. More accurate tests, which can return results in several hours, must be performed in specialized labs.
There is no cure for either the cold or the flu at this time. Antibiotics don't work against them because they kill bacteria, and as we discussed, both the flu and a cold are caused by viruses. Your doctor may offer to treat you with a class of drugs known as antivirals, including Tamiflu, Relenza, Flumadine and Xofluza, a newer drug approved by the Food and Drug Administration in 2018. Antivirals won't cure you, but when taken soon enough after infection - about two days - they may lessen the severity of symptoms and shorten the duration of illness by a few days.
As always, we recommend getting the flu vaccine every year. It's not too late!
• Dr. Eve Glazier is an internist and associate professor of medicine at UCLA Health. Dr. Elizabeth Ko is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu.