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The common cold is a mild infection of your upper respiratory tract (which includes your nose and throat). Colds are probably the most common illness. Adults have an average of 2-3 colds per year, and children have even more. Colds are more common in the winter and spring, but you can get them at any time.

More than 200 different viruses can cause a cold, but rhinoviruses are the most common type. The viruses that cause colds are very contagious. They can spread from person to person through the air and close personal contact. You can also get infected when you touch something that has the virus on it and then touch your eyes, mouth, or nose. For example, you could get a cold after you shake hands with someone who has a cold or touch a doorknob that has the germs on it, and then touch your face.

The symptoms of a common cold usually include:

• Sneezing
• Stuffy nose (congestion)
• Runny nose
• Sore throat
• Coughing
• Headache

The symptoms usually start a few days after you become infected with the virus. Some symptoms can last for 10-14 days.

There is no cure for the common cold. But there are treatments that can make you feel better while you wait for the cold to go away on its own:

• Getting lots of rest.
• Drinking plenty of fluids.
• Using a clean humidifier or cool mist vaporizer.
• Gargling with warm salt water.
• Using saline nose drops or sprays.
• Taking over-the-counter pain or cold and cough medicines. But you need to be careful with certain medicines:
  • Children and teens should not take aspirin.
  • Some cold and cough medicines contain ingredients that are not recommended for children. Talk with your child's health care provider before giving your child any cold and cough medicines.
  • Some cold and cough medicines contain pain relievers. If you also take a separate pain reliever with these medicines, you could be getting a dangerous amount of the pain reliever. Read the labels on the medicines and follow the instructions carefully. If you have questions, ask your provider or a pharmacist.

Antibiotics will not help with a cold. Antibiotics help with bacterial infections, not with viral infections such as colds.

Most people who have a cold will feel better after a week or two. However, some people who get a cold may develop other illnesses, such as bronchitis or pneumonia. This is more common in people with weakened immune systems, asthma, or other respiratory conditions. Contact your provider if you or your child have symptoms that concern you, such as:

• Trouble breathing or fast breathing
• Dehydration
• Fever that lasts longer than 4 days
• Symptoms that last more than 10 days without improvement
• Symptoms, such as fever or cough, that improve but then return or worsen
• Worsening of chronic medical conditions

There is no vaccine to protect against the common cold. But you may be able to reduce your risk of getting or spreading a cold by:

• Washing your hands often with soap and water for at least 20 seconds.
• Avoiding touching your face, nose, or mouth with unwashed hands.
• Avoiding close contact, such as kissing, shaking hands, and sharing cups and eating utensils, with others if you are sick or they are sick.
• Cleaning and disinfecting surfaces that you frequently touch.
• Covering coughs and sneezes with a tissue. Then throw away the tissue and wash your hands.
• Staying home when sick.

Centers for Disease Control and Prevention

Your nose is important to your health. It filters the air you breathe, removing dust, germs, and irritants. It warms and moistens the air to keep your lungs and tubes that lead to them from drying out. Your nose also contains the nerve cells that help your sense of smell. When there is a problem with your nose, your whole body can suffer. For example, the stuffy nose of the common cold can make it hard for you to breathe, sleep, or get comfortable.

Many problems besides the common cold can affect the nose. They include:

• Deviated septum - a shifting of the wall that divides the nasal cavity into halves
• Nasal polyps - soft growths that develop on the lining of your nose or sinuses
• Nosebleeds
• Rhinitis - inflammation of the nose and sinuses sometimes caused by allergies. The main symptom is a runny nose.
• Nasal fractures, also known as a broken nose

Antibiotics are medicines that fight bacterial infections in people and animals. They work by killing the bacteria or by making it hard for the bacteria to grow and multiply.

Antibiotics can be taken in different ways:

• Orally (by mouth). This could be pills, capsules, or liquids.
• Topically. This might be a cream, spray, or ointment that you put on your skin. It could also be eye ointment, eye drops, or ear drops.
• Through an injection or intravenously (IV). This is usually for more serious infections.

Antibiotics only treat certain bacterial infections, such as strep throat, urinary tract infections, and E. coli.

You may not need to take antibiotics for some bacterial infections. For example, you might not need them for many sinus infections or some ear infections. Taking antibiotics when they're not needed won't help you, and they can have side effects. Your health care provider can decide the best treatment for you when you're sick. Don't ask your provider to prescribe an antibiotic for you.

Antibiotics do not work on viral infections. For example, you shouldn't take antibiotics for:

• Colds and runny noses, even if the mucus is thick, yellow, or green
• Most sore throats (except strep throat)
• Flu
• Most cases of bronchitis

The side effects of antibiotics range from minor to very severe. Some of the common side effects include:

• Rash
• Nausea
• Diarrhea
• Yeast infections

More serious side effects can include:

• C. diff infections, which cause diarrhea that can lead to severe colon damage and sometimes even death
• Severe and life-threatening allergic reactions
• Antibiotic resistance infections

Call your health care provider if you develop any side effects while taking your antibiotic.

You should only take antibiotics when they are needed because they can cause side effects and can contribute to antibiotic resistance. Antibiotic resistance happens when the bacteria change and become able to resist the effects of an antibiotic. This means that the bacteria continue to grow.

When you take antibiotics, it is important that you take them responsibly:

• Always follow the directions carefully. Finish your medicine even if you feel better. If you stop taking them too soon, some bacteria may survive and re-infect you.
• Don't save your antibiotics for later.
• Don't share your antibiotic with others.
• Don't take antibiotics prescribed for someone else. This may delay the best treatment for you, make you even sicker, or cause side effects.

Centers for Disease Control and Prevention

Cold and cough medicines can help relieve symptoms of a common cold. The symptoms of a cold can include a sore throat, stuffy or runny nose, sneezing, and coughing.

You don't usually need to treat a cold or the cough that it causes. You can't cure a cold, and antibiotics won't help you get better. But sometimes the symptoms can keep you awake or cause a lot of discomfort. In that case, cold and cough medicines can sometimes be helpful.

There are lots of different cold and cough medicines, and they do different things:

• Nasal decongestants - unclog a stuffy nose
• Cough suppressants - quiet a cough
• Expectorants - loosen mucus in your lungs so you can cough it up
• Antihistamines - stop runny noses and sneezing
• Pain relievers - ease fever, headaches, and minor aches and pains

Before taking these medicines, read the labels and follow the instructions carefully. Many cold and cough medicines contain the same active ingredients. For example, some of them include pain relievers. If you are taking these medicines and are also taking a separate pain reliever, you could be getting a dangerous amount of the pain reliever.

Do not give cold or cough medicines to children under two, and don't give aspirin to children.

If you decide that you don't want to take cold and cough medicines, there are other ways to feel better:

• Drink lots of fluids
• Get plenty of rest
• Use a cool mist humidifier
• Use saline nose drops or sprays
• Use nasal suctioning with a bulb syringe, which can be very helpful in children under a year old

Centers for Disease Control and Prevention

It is hard when your baby is sick. Common health problems in babies include colds, coughs, fevers, and vomiting. Babies also commonly have skin problems, like diaper rash or cradle cap.

Many of these problems are not serious. It is important to know how to help your sick baby, and to know the warning signs for more serious problems. Trust your intuition - if you are worried about your baby, call your health care provider right away.

During pregnancy, some common infections like the common cold or a skin infection do not usually cause serious problems. But other infections can be dangerous to you, your baby, or both. Some infections may lead to preterm birth and low birth weight babies. Others can cause serious illness, birth defects, and lifelong disabilities, such as hearing loss or learning problems.

Some of the infections that can be dangerous during pregnancy include:

• Bacterial vaginosis (BV)
• Group B strep (GBS)
• Hepatitis
• Sexually transmitted diseases
• Toxoplasmosis
• Urinary tract infections
• Yeast infections
• Zika virus

To try to prevent infections,:

• Don't eat raw or undercooked meat
• Don't share food or drinks with other people
• Wash your hands frequently
• Don't empty cat litter. Cats can transmit toxoplasmosis.

If you do get an infection during pregnancy, contact your health care provider about how best to protect you and your baby. Only some medicines are safe during pregnancy.

Germs, or microbes, are found everywhere - in the air, soil, and water. There are also germs on your skin and in your body. Many of them are harmless, and some can even be helpful. But some of them can make you sick. Infectious diseases are diseases that are caused by germs.

There are four main types of germs:

• Bacteria are one-celled germs that multiply quickly. They may give off toxins, which are harmful chemicals that can make you sick. Strep throat and urinary tract infections are common bacterial infections.
• Viruses are tiny capsules that contain genetic material. They invade your cells so that they can multiply. This can kill, damage, or change the cells and make you sick. Viral infections include HIV and the common cold.
• Fungi are primitive plant-like organisms such as mushrooms, mold, mildew, and yeasts. Athlete's foot and yeast infections are common fungal infections.
• Parasites are animals or plants that survive by living on or in other living things. Malaria and head lice are infections that are caused by parasites.

There are many different ways that you can get an infectious disease:

• Through direct contact with a person who is sick. This includes kissing, touching, sneezing, coughing, and sexual contact. Pregnant people can also pass some germs along to their babies.
• Through indirect contact, when you touch something that has germs on it. For example, you could get germs if someone who is sick touched a door handle, and then you touch it.
• Through insect or animal bites.
• Through contaminated food, water, soil, or plants.

Infectious diseases can cause many different symptoms. Some are so mild that you may not even notice any symptoms, while others can be life-threatening.

You can take steps to prevent many infectious diseases:

• Get vaccinated
• Wash your hands often
• Pay attention to food safety
• Avoid contact with wild animals
• Practice safe sex (use a condom every time you have anal, vaginal, or oral sex)
• Don't share items such as toothbrushes, combs, and straws

Pneumonia is an infection in one or both of the lungs. It causes the air sacs of the lungs to fill up with fluid or pus. It can range from mild to severe, depending on the type of germ causing the infection, your age, and your overall health.

Bacterial, viral, and fungal infections can cause pneumonia.

Bacteria are the most common cause. Bacterial pneumonia can occur on its own. It can also develop after you've had certain viral infections such as a cold or the flu. Several different types of bacteria can cause pneumonia, including:

• Streptococcus pneumoniae
• Legionella pneumophila; this pneumonia is often called Legionnaires' disease
• Mycoplasma pneumoniae
• Chlamydia pneumoniae
• Haemophilus influenzae

Viruses that infect the respiratory tract may cause pneumonia. Viral pneumonia is often mild and goes away on its own within a few weeks. But sometimes it is serious enough that you need to get treatment in a hospital. If you have viral pneumonia, you are at risk of also getting bacterial pneumonia. The different viruses that can cause pneumonia include:

• Respiratory syncytial virus (RSV)
• Some common cold and flu viruses
• SARS-CoV-2, the virus that causes COVID-19

Fungal pneumonia is more common in people who have chronic health problems or weakened immune systems. Some of the types include:

• Pneumocystis pneumonia (PCP)
• Coccidioidomycosis, which causes valley fever
• Histoplasmosis
• Cryptococcus

Anyone can get pneumonia, but certain factors can increase your risk:

• Age; the risk is higher for children who are age 2 and under and adults age 65 and older
• Exposure to certain chemicals, pollutants, or toxic fumes
• Lifestyle habits, such as smoking, heavy alcohol use, and malnourishment
• Being in a hospital, especially if you are in the ICU. Being sedated and/or on a ventilator raises the risk even more.
• Having a lung disease
• Having a weakened immune system
• Have trouble coughing or swallowing, from a stroke or other condition
• Recently being sick with a cold or the flu

The symptoms of pneumonia can range from mild to severe and include:

• Fever
• Chills
• Cough, usually with phlegm (a slimy substance from deep in your lungs)
• Shortness of breath
• Chest pain when you breathe or cough
• Nausea and/or vomiting
• Diarrhea

The symptoms can vary for different groups. Newborns and infants may not show any signs of the infection. Others may vomit and have a fever and cough. They might seem sick, with no energy, or be restless.

Older adults and people who have serious illnesses or weak immune systems may have fewer and milder symptoms. They may even have a lower than normal temperature. Older adults who have pneumonia sometimes have sudden changes in mental awareness.

Sometimes pneumonia can cause serious complications such as:

• Bacteremia, which happens when the bacteria move into the bloodstream. It is serious and can lead to septic shock.
• Lung abscesses, which are collections of pus in cavities of the lungs
• Pleural disorders, which are conditions that affect the pleura. The pleura is the tissue that covers the outside of the lungs and lines the inside of your chest cavity.
• Kidney failure
• Respiratory failure

Sometimes pneumonia can be hard to diagnose. This is because it can cause some of the same symptoms as a cold or the flu. It may take time for you to realize that you have a more serious condition.

Your health care provider may use many tools to make a diagnosis:

• A medical history, which includes asking about your symptoms
• A physical exam, including listening to your lungs with a stethoscope
• Various tests, such as
  • A chest x-ray
  • Blood tests such as a complete blood count (CBC) to see if your immune system is actively fighting an infection
  • A Blood culture to find out whether you have a bacterial infection that has spread to your bloodstream

If you are in the hospital, have serious symptoms, are older, or have other health problems, you may also have more tests, such as:

• Sputum test, which checks for bacteria in a sample of your sputum (spit) or phlegm (slimy substance from deep in your lungs).
• Chest CT scan to see how much of your lungs is affected. It may also show if you have complications such as lung abscesses or pleural effusions.
• Pleural fluid culture, which checks for bacteria in a fluid sample that was taken from the pleural space
• Pulse oximetry or blood oxygen level test, to check how much oxygen is in your blood
• Bronchoscopy, a procedure used to look inside your lungs' airways

Treatment for pneumonia depends on the type of pneumonia, which germ is causing it, and how severe it is:

• Antibiotics treat bacterial pneumonia and some types of fungal pneumonia. They do not work for viral pneumonia.
• In some cases, your provider may prescribe antiviral medicines for viral pneumonia
• Antifungal medicines treat other types of fungal pneumonia

You may need to be treated in a hospital if your symptoms are severe or if you are at risk for complications. While there, you may get additional treatments. For example, if your blood oxygen level is low, you may receive oxygen therapy.

It may take time to recover from pneumonia. Some people feel better within a week. For other people, it can take a month or more.

Vaccines can help prevent pneumonia caused by pneumococcal bacteria or the flu virus. Having good hygiene, not smoking, and having a healthy lifestyle may also help prevent pneumonia.

NIH: National Heart, Lung, and Blood Institute

Viruses are very tiny germs. They are made of genetic material (either DNA or RNA) inside of a protein coating. There are a huge number of viruses on earth. Only a small number of them can infect humans. Those viruses can infect our cells, which may cause disease. Some of the diseases that viruses can cause include the common cold, the flu, COVID-19, and HIV.

Viruses can be spread in different ways:

• Through droplets and particles that are breathed out by someone who has the infection. You might breathe in the droplets or particles, or they could land on your mouth, nose, or eyes.
• By touching surfaces or objects that have the virus on them and then touching your mouth, nose, or eyes.
• From the pregnant parent to the baby during pregnancy.
• Through contaminated food or water.
• By being bitten by an infected insect or animal.
• Through sexual contact (usually vaginal, anal and oral sex) with someone who has the infection.

Viruses are like hijackers. They invade living, normal cells. They then use those cells to multiply (make copies of themselves). This process is also called replication. The process can kill, damage, or change the infected cells. Sometimes this can make you sick. The symptoms can range from mild to very severe. Other times, your immune system may be able to fight it off and you may not have any symptoms.

Each different virus usually only infects one type of cell in your body. For example, hepatitis viruses affect the cells in the liver. HIV infects a certain type of immune system cell.

For most viral infections, treatments can only help with symptoms while you wait for your immune system to fight off the virus. There are antiviral medicines to treat some viral infections. Antibiotics do not work for viral infections.

Vaccines can help prevent you from getting many viral diseases. You may be able to prevent some viral infections by:

• Proper hand washing.
• Paying attention to food safety.
• Cleaning surfaces that may be infected with germs.
• Avoiding contact with wild animals.
• Preventing insect bites by using insect repellent when you go outdoors. If you travel to an area that has a high risk of diseases from insect bites, also wear long pants, shirts, and socks.
• Practicing safe sex (using a condom every time you have anal, vaginal, or oral sex).
• Avoiding close contact with people who are sick.

Bronchitis is an inflammation of the bronchial tubes, the airways that carry air to your lungs. It causes a cough that often brings up mucus. It can also cause shortness of breath, wheezing, a low fever, and chest tightness. There are two main types of bronchitis: acute and chronic.

Most cases of acute bronchitis get better within several days. But your cough can last for several weeks after the infection is gone.

The same viruses that cause colds and the flu often cause acute bronchitis. These viruses spread through the air when people cough, or though physical contact (for example, on unwashed hands). Being exposed to tobacco smoke, air pollution, dusts, vapors, and fumes can also cause acute bronchitis. Less often, bacteria can also cause acute bronchitis.

To diagnose acute bronchitis, your health care provider will ask about your symptoms and listen to your breathing. You may also have other tests.

Treatments include rest, fluids, and aspirin (for adults) or acetaminophen to treat fever. A humidifier or steam can also help. You may need inhaled medicine to open your airways if you are wheezing. Antibiotics won't help if the cause is viral. You may get antibiotics if the cause is bacterial.

NIH: National Heart, Lung, and Blood Institute