Colds and Flu


The common cold is caused by a large number of viruses that may occur at any time of the year. Influenza (flu) is a viral infection caused by the influenza A or B virus, which occurs mainly in the winter. Both A and B viruses are contagious respiratory illnesses.

The respiratory viruses that cause colds and flu are both contagious but they differ in how sick they can make you. Unlike colds, flu can cause complications such as pneumonia.

While there is no vaccine for colds, flu has a vaccine available annually to help decrease your chances of coming down with the infection or to make the illness less debilitating if you do become infected.


Transmission of colds and flu

Cold and flu viruses are contagious and are transmitted three ways:

Having direct contact. People carry the cold virus on their hands. If a person with the virus shakes your hand and you then touch your eyes, nose, or mouth, you may infect yourself with the virus.

Touching contaminated surfaces. Some cold viruses can live on surfaces like telephones, door handles, and tables. If you touch a surface that has been contaminated by a person who was ill and you then touch your eyes, nose, or mouth, you may infect yourself with the virus.

Inhaling the cold virus. This may occur when you breathe in air that contains the virus from an infected person who has recently sneezed, coughed, or exhaled into the air.

Neither of these illnesses is caused by being cold.

Symptoms and Diagnosis


There is no special test for the common cold. We can make the diagnosis of the common cold based on your symptoms. It takes 1 to 3 days to develop the symptoms after you have been exposed to a person who has been ill or touched a surface contaminated by someone with a cold.

Symptoms may vary, but they typically include:

  • Sore throat
  • Nasal stuffiness or congestion
  • Runny nose
  • Postnasal drip
  • Sneezing

Cough and muscle aches may occur as well. Sometimes, you may get eye irritation. You may have other symptoms including low-grade fever or chills. We often use the term "upper respiratory infection" (URI) when referring to colds. Usually, the cold will last 3 to 7 days, but it may persist for as long as 2 weeks. If you smoke or have other chronic health conditions, you may have more severe or prolonged symptoms.


Every year in the United States, on average 5 to 20 percent of the population gets the flu; approximately 200,000 people are hospitalized from flu-related complications, and about 36,000 people die from flu-related causes.

A flu diagnosis can be determined by your symptoms. Typically, if you have the flu, you will report the sudden development of:

  • Fever (usually high)
  • Headache
  • Nonproductive cough (it does not bring up mucus)
  • Significant muscle pains, including low-back pain and weakness 

Flu can cause complications such as pneumonia or other major problems for people who have other chronic conditions like heart disease, lung disease, diabetes, active cancer, or immune system problems like HIV. If this is the case for you, it is especially important for everyone who is older than 6 months to get a flu vaccine every year.

The flu is more serious than a cold. Complications from the flu can cause death in some vulnerable individuals including infants and young children up to 5 years old, pregnant women, the elderly, and those with chronic illnesses. Because of the nature of their job, healthcare workers are also at higher risk for getting the flu.

While you usually will see improvement in 2 to 5 days, the illness can last for a week or more. Some individuals may continue to feel weak and tired for several weeks. 

We may diagnose flu either by your symptoms or by taking a sample of your nasal mucus and testing it for the influenza A or B virus. We often do this early in the winter, before the flu season begins. Once there is a flu outbreak and many people have already been diagnosed and we know the range of symptoms, the diagnosis is made based on your symptoms alone.

Other Preventive Measures

Preventing cold and flu

The best way to decrease your chances of developing a cold or flu is to:

Avoid touching your eyes, nose, or mouth, as these are the entry points for the virus into your body.

Wash your hands regularly and thoroughly with soap and warm water or use an alcohol-based hand gel.

Take these steps regularly, especially if you have encountered someone who is ill.

To prevent the spread of cold or flu:

  • Cover your mouth and nose when you cough and sneeze.
  • Sneeze or cough into your elbow rather than your hand.
  • Wash your hands thoroughly.
  • Avoid close contact with people who are already sick.
  • Stay home from work and school and avoid public places if you're feeling sick to help prevent others from getting the flu.

Adults with flu can spread it to other adults for up to 5 days after symptoms start. Kids may be contagious for longer periods.

The Flu Vaccine

The best way to avoid catching the flu is to get a flu vaccination every year.

The Centers for Disease Control and Prevention (CDC) and Kaiser Permanente strongly recommend that everyone older than 6 months get a seasonal flu vaccine when available. It will help prevent you from getting the flu and infecting others. To keep you healthy, Kaiser Permanente will send you a reminder to get the vaccine.

There are 2 ways you can receive your flu vaccine: the flu shot—given as an injection in the upper arm—or the  nasal spray—given as a mist sprayed into the nose. Both are highly effective ways of preventing the flu. Besides the way that the vaccine is given, the main difference between the two is that the flu shot contains inactive (dead) virus, while the flu nasal spray contains live attenuated virus that has been weakened so it cannot make you sick. The shot cannot cause the flu, and the spray has not been shown to spread the weakened virus.

The flu shot is safe for adults and all children who are older than 6 months. The shot is safe for healthy people, pregnant women, and people with long-term health conditions like asthma, diabetes, and heart disease. The flu nasal spray is safe for healthy people between 2 and 49 years of age who are not pregnant and who do not have long-term medical conditions.

The flu vaccine is usually available in September. Call the flu shot hotline, 1-800-573-5811 (1-800-KP-FLU-11) or visit the flu clinic page to find the closest Kaiser Permanente facility and where and when to get a flu vaccination. Flu vaccinations are free to all Kaiser Permanente members.

Prevention using Complementary and Alternative Medicine

In addition to good hygiene and flu vaccinations, there are other approaches that may help prevent colds and flu. They include:

Physical activity. Some research suggests that regular moderate-intensity exercise like brisk walking for 30 minutes each day for 1 year may decrease the number of colds per year. 

Vitamin C. Research shows that vitamin C at a dose of 500 mg daily may help prevent colds. It has not been shown to help when you already have a cold.

Echinacea. Research shows no benefit.


Unfortunately, there is no cure for a cold or flu. For flu, if diagnosed within the first 48 hours of illness, there are some antiviral drugs that can be effective at reducing severity and length of symptoms.

For colds, the best treatment is home care and allowing the virus to run its course. The good news is that there are some home remedies as well as over-the-counter medications that can lessen your symptoms as you wait to get better. 

  • Get extra rest. You can return to work once symptoms have improved and you are no longer running a fever, but slow down and try to take it easy.
  • Drink lots of noncaffeinated fluids. Hot herbal tea, warm water and chicken soup is especially good for congestion (runny or stuffy nose).
  • Take over-the-counter medication to soothe your cold and flu symptoms.

Use caution. If you decide to use a multisymptom cold medication, be sure to read the active ingredients section. Many times, individuals mistakenly take acetaminophen for fever or muscle aches without realizing that it is included in the multisymptom cold remedy. Too much medicine is not safe.

Antibiotic medications

Antibiotics do not help with a common cold since they are effective only against bacterial infections-they do not treat viral infections. Taking antibiotics when they are not needed can cause bacteria to become resistant to the drugs. These medications also can have side effects, which in rare cases can be serious.

Antiviral medications

There are no antiviral medicines available for colds.

There are antiviral prescription medications for flu that may be used in certain circumstances. You must start these medications within 2 days of developing symptoms. They may decrease the length of the illness and the severity of symptoms. As with all medications, there are side effects to consider.  We can help determine whether you might benefit from antiviral treatment for flu.

If you're pregnant

We know that pregnant women have a greater chance of developing complications from flu. Be on the lookout for flu symptoms: fever, cough, sore throat, body aches, headache, chills, and fatigue. If you're pregnant and catch the flu, you may be eligible for treatment with antiviral medication. This can make your flu milder and make you feel better faster, and may prevent complications. To be most effective, antiviral treatment should start within 48 hours of first symptoms or exposure to someone with the flu.

Complementary and Alternative Medicine Treament

General recommendations for relief. Get plenty of rest. Drink plenty of fluids. Hot herbal tea, warm water, and chicken soup are helpful with runny nose or stuffy nose symptoms.

Smoking. If you smoke, cut down or, even better, quit. Ask us. We can help.

Heated humidified air. Research shows that this may reduce symptoms. You can use a humidifier or steam from a hot shower.

Saline sprays. Research shows no benefit. The spray may cause irritation and make symptoms worse. However, saline nasal rinses can be helpful.

Vitamin C. Research does not show any benefit for treatment; however, it may be helpful for prevention.

Zinc. Research shows little if any benefit. The lozenges may cause a metallic taste. The inhaled form may cause permanent loss of smell.

If you have an emergency medical condition, call 911 or go to the nearest hospital. An emergency medical condition is any of the following:
(1) a medical condition that manifests itself by acute symptoms of sufficient severity (including severe pain) such that you could reasonably expect the absence of immediate medical attention to result in serious jeopardy to your health or body functions or organs; (2) active labor when there isn't enough time for safe transfer to a Plan hospital (or designated hospital) before delivery, or if transfer poses a threat to your (or your unborn child's) health and safety, or (3) a mental disorder that manifests itself by acute symptoms of sufficient severity such that either you are an immediate danger to yourself or others, or you are not immediately able to provide for, or use, food, shelter, or clothing, due to the mental disorder.

This information is not intended to diagnose health problems or to take the place of specific medical advice or care you receive from your physician or other health care professional. If you have persistent health problems, or if you have additional questions, please consult with your doctor. If you have questions or need more information about your medication, please speak to your pharmacist. Kaiser Permanente does not endorse the medications or products mentioned. Any trade names listed are for easy identification only.