Having an infectious disease causes you to transmit the disease to other people. When you feel sick, knowing if your disease is contagious can prevent you from infecting others. Upper respiratory tract diseases, such as colds and flu, are caused by viruses and are easily transmitted to other people. Many infections caused by bacteria can also be highly contagious. If you know your disease is contagious, preventive measures can help to prevent the spread of the disease.
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Part 1 of 4: Identifying the Symptoms of Infectious Diseases
Step 1. Check your body temperature
The normal temperature range is between 36.5° to 37.5° C. If your temperature is above that, you may have a fever and may infect other people. Getting a fever with a cold is not the same as the fever associated with the flu, but it does mean your illness is contagious.
- Fever is your body's way of fighting infection. Body temperature can be measured orally, anus, in the ear, or under the arm, and results may vary slightly depending on each method. Flu-related fevers can range from 37.7° to 38.8°C, and will be even higher in children. Those caused by the flu last for 3 to 4 days in most cases.
- Body temperature is regulated through a structure in the brain called the hypothalamus. When infected, the hypothalamus increases body heat to help get rid of the invading virus or bacteria.
Step 2. Check for mucus and nasal secretions
Thick or yellow/green mucus is a strong indication that there is an upper respiratory tract infection accompanied by inflammation of the respiratory tract. It also means that the disease you have is most likely contagious.
- Specific respiratory diseases involving thick or discolored mucus and nasal secretions include colds, sinusitis (inflammation of the sinuses), epiglottitis (inflammation of the epiglottitis), laryngitis (inflammation of the larynx, and bronchitis (inflammation of the bronchi).
- The immune system increases the production of mucus in your nose to expel disease. This causes your nose to feel stuffy, and indicates the disease is contagious.
- If thick or discolored mucus doesn't go away in about a week, see a doctor. Your doctor can perform tests to evaluate the cause of your symptoms, prescribe treatment, and determine if the disease is contagious.
Step 3. Watch for skin rashes
Certain skin rashes are often a sign of an infectious disease. A rash that spreads over most of the body can be an allergy or a virus. A viral rash indicates you have an infectious disease, such as chickenpox or measles.
- There are two ways the viral rash spreads. The viral symmetrical rash starts from the extremities, at both ends of the body, then spreads to the middle of the body. The viral rash starts from the chest or back, then spreads to the outer parts of the body such as the arms and legs.
- The viral rash follows a pattern of spread, either outward or inward, as just described. Rashes caused by allergies can appear anywhere on the body and do not have a specific pattern of distribution.
Step 4. Watch out for diarrhea accompanied by a low-grade fever
Diarrhea can be a sign of an infectious disease, especially if it is accompanied by vomiting and a low-grade fever. Diarrhea, vomiting, and low-grade fever can be signs of gastroenteritis, often referred to as the stomach flu, or signs of rotavirus or coxsackievirus, which are all contagious.
- There are two types of diarrhea: acute and non-acute. Symptoms of non-acute diarrhea include abdominal bloating or cramping, loose stools, a sense of urgency to have a bowel movement, nausea, and vomiting. Usually, diarrhea causes you to have bowel movements at least 3 times a day.
- Acute diarrhea includes all the symptoms of non-acute diarrhea plus blood, mucus, or undigested food in the stool, accompanied by fever and weight loss.
Step 5. Watch for pain behind the forehead, cheeks and in the nose
A normal headache is usually not an indication of an infectious disease. However, certain types of headaches (pain in the face and forehead) can be a warning that you have a contagious disease.
The headache that accompanies the flu, and sometimes a cold, results from persistent pain in the forehead, cheeks and bridge of the nose. Swelling and buildup of mucus in the sinus area causes discomfort. The headache will get worse and may get worse when you bend over
Step 6. Notice if your sore throat is accompanied by a runny nose
If you have an infectious disease, such as the flu or a cold, a sore throat is often accompanied by a runny nose.
- A sore throat is sometimes caused by a buildup of mucus, as fluid from the sinuses drips down the back of your throat, causing redness and irritation. The throat feels swollen, irritated, and painful.
- When a sore throat and runny nose are accompanied by wheezing and itchy, watery eyes, there's a good chance you have an allergy and not a contagious virus. Throat discomfort caused by allergies still comes from the build-up of mucus, but the throat feels dry and itchy.
Step 7. Watch for drowsiness and loss of appetite
Infectious diseases can cause you to feel very tired or sleepy, and to lose your appetite. Sleeping a lot and eating less are two ways your body conserves energy to fight infection.
Part 2 of 4: Putting Symptoms Together
Step 1. Recognize the symptoms of influenza, or flu
Symptoms of the flu include fever, headache, general aches and pains, extreme tiredness, and sometimes nasal congestion, runny nose, sneezing, coughing, and chest tightness. In influenza, or the flu, symptoms start more suddenly, develop more quickly, and are more severe than cold symptoms. The flu can also cause serious complications.
A person who has the flu will be infectious for a day or two before symptoms begin, and will remain infectious for 5 to 7 days after they appear. The CDC considers the disease to be contagious until the fever returns to normal, without the aid of medication, for 24 to 48 hours. If other symptoms persist, such as problems with coughing, runny nose, and sneezing, then you may still be infectious
Step 2. Identify the symptoms of a cold
Typical symptoms that occur with a cold include sore throat, stuffy or runny nose, congestion, sneezing, mild chest tightness, fatigue, and body aches. Colds are contagious from 1-2 days before symptoms appear, then continue to be contagious for the next 2 to 3 days when symptoms are at their peak.
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More than 200 viruses have been identified that cause people to catch colds. This type of upper respiratory illness makes you feel bad, irritated and uncomfortable, but is usually not associated with serious complications. Symptoms can stay for up to 10 days, but the most contagious time is in the first few days when symptoms are particularly strong.
Tell when You Are Contagious Step 8
Step 3. Watch for combined symptoms
A cluster of symptoms such as diarrhea, nausea, and vomiting along with muscle aches and headaches can signal you have gastroenteritis, sometimes called the stomach flu, or even food poisoning. Gastroenteritis and food poisoning have similar symptoms. It's hard to tell which one you're suffering from. However, stomach flu, or gastroenteritis is contagious, while food poisoning is not.
Step 4. Pay attention to those around you who have been sick
Most infectious diseases can last for 1 or 2 days before symptoms appear. It will be easier to find out which illness you have by understanding the illness that someone around you has recently had, even if they weren't already sick when you were around them.
Also consider the season of the year. Many infectious diseases are more common during certain times of the year. Flu season in the United States is generally from November to March. Other diseases may occur at certain times in certain countries or regions. Plus, seasonal allergens can vary depending on where you live
Step 5. Rule out seasonal allergies
Some people have a strong upper respiratory system caused by seasonal airborne allergens. This type of disease is not contagious. Allergy symptoms are almost the same as flu and cold symptoms.
- Symptoms of allergies include tiredness, stuffy nose, runny nose, sneezing, sore throat and cough. While allergy symptoms can make you feel bad, you are not carrying an infectious disease. Your doctor can help you by performing laboratory tests to identify the cause of your allergy, and by prescribing the right medication.
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At first, it may be difficult to tell the difference between symptoms of a cold, flu, or seasonal allergies. After a day or two, the symptoms will change. The speed at which your symptoms change and the addition of new ones that develop can help you determine whether your symptoms are from an infectious disease such as a cold or flu, or are caused by seasonal airborne allergens that are not contagious.
Tell when You Are Contagious Step 10 - Allergies are caused by an overactive immune system. Certain substances such as pollen, dust, animal dander, and some foods, trigger the immune system to fight them as if they were harmful substances in our body.
- When that happens the body releases histamine to fight off the intruders. Histamine causes symptoms similar to a respiratory infection, such as sneezing, coughing, runny nose, stuffy nose, itchy and watery eyes, sore throat, wheezing and headache.
Part 3 of 4: Preventing the Spread of Infectious Diseases
Step 1. Get your annual flu vaccine
Scientists research and develop flu vaccines designed to prevent infection from possible flu viruses. Each year, the vaccine will be different, so getting the vaccine one year doesn't protect you from flu season the following year. Getting the flu vaccine is key in controlling the spread of the flu.
The flu vaccine protects you from the flu, not from other infectious diseases you might catch
Step 2. Wash your hands
Upper respiratory tract diseases, such as the common cold or flu, are spread from person to person. A common way the disease is spread is touching someone or something that has been contaminated with the virus.
Step 3. Use soap and water
Wash it off with warm water, and place the soap in the palm of your hand. Make a lather by rubbing the soap for at least 15 seconds. Make sure the foam covers the entire surface of your hand, including between your fingers. Then rinse your hands thoroughly, use a dry paper towel, and use a tissue to turn off the faucet. Throw the tissue in the trash.
Step 4. Clean your hands with alcohol gel
Pour the alcohol gel over your dry palms. Rub your hands over the entire surface until the gel dries. This takes about 15 to 20 seconds.
Step 5. Avoid contact with people who are sick
The flu virus can spread from a sick person as far as 1.8 m. Coughs and sneezes create tiny droplets that can fly through the air, then land on a person's hands, mouth, nose, or be inhaled directly into their lungs.
Step 6. Pay attention to the surface you touch
Doorknobs, desks, pencils, and other objects can carry viral germs from one person to another. After you touch an object that has been contaminated with the virus, you are very likely to touch your mouth, eyes, or nose. This method causes unwanted viruses to enter your body. The flu virus can live for 2 to 8 hours on surfaces.
Step 7. Protect yourself and others from exposure
If you are sick, avoid contact with other people until your symptoms resolve or your doctor says you are no longer contagious.
In the United States, estimates suggest that between 5% and 20% of the population catch the flu each year. More than 200,000 people are hospitalized every year for complications and, every year, thousands die. The elderly, pregnant women, and people with low immune systems, have the greatest risk of developing complications. Protecting yourself from exposure, and preventing disease from infecting others, can save lives
Step 8. Stay at home, isolated from others
Try to stay indoors while at home, separated from other family members (especially children) to avoid spreading disease.
Step 9. Cover your mouth when you cough or sneeze
Cover it with a tissue when you cough or sneeze, or even with your arm near your elbow, so you don't spread infected droplets into the air.
Step 10. Avoid sharing things
Sheets, towels, dishes and utensils must be washed carefully before being used by others.
Part 4 of 4: Beware of Other Infectious Diseases
Step 1. Beware of other infectious diseases
While the flu and colds are common to most people, there are many other infectious diseases, some of them serious, that should not be ignored. Doctors, or other healthcare providers, are a great resource for recognizing any developing disease or symptoms that may be contagious.
Step 2. Be wary of those around you who have been diagnosed with a serious infection
Some forms of hepatitis can be contagious, as can some forms of meningitis. This condition is serious and should not be ignored. If someone you know is diagnosed with an infectious disease, consult your doctor to see if you are at risk.
Step 3. Identify infectious childhood infections
Most children receive vaccinations at an early age to avoid contracting serious illnesses, but sometimes infectious diseases can still be a problem. Discuss evidence of infection or disease with your doctor or pediatrician.
Tips
- Most employers, schools, and daycare centers have published guidelines on what to do if you have an infectious disease.
- The Centers for Disease Control and Prevention recommends staying at home, away from other people, for at least 24 hours after the fever returns to normal without the help of medication.
- Health facilities, such as hospitals and nursing homes, have rules and guidelines for visitors to help prevent the spread of infectious diseases.
- People wishing to visit someone who is sick, either at home or in a hospital facility, should follow the facility's guidelines, or consider visiting when the infectious period has passed.
- Infectious Diseases develop from the incubation period when the symptoms have disappeared. Most infectious diseases have an early period when the disease begins to spread and people are not yet aware that they have it.
- When in doubt, it's better to consider yourself infected and stay away from other people until your illness is cured.
- Visit a doctor to be tested whether your disease is contagious or not. It is difficult to distinguish between colds, flu and allergies and between stomach flu and food poisoning.
