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A fever is a body temperature that is higher than normal. A normal temperature can vary from person to person, but it is usually around 98.6 °F (37 °C). A fever is not a disease. It is usually a sign that your body is trying to fight an illness or infection.

Infections cause most fevers. You get a fever because your body is trying to kill the virus or bacteria that caused the infection. Most of those bacteria and viruses do well when your body is at your normal temperature. But if you have a fever, it is harder for them to survive. Fever also activates your body's immune system.

Other causes of fevers include:

• Medicines, including some antibiotics, blood pressure medicines, and anti-seizure medicines
• Heat illness
• Cancers
• Autoimmune diseases
• Some childhood vaccines

Treatment depends on the cause of your fever. If the fever is very high, your health care provider may recommend taking an over-the-counter medicine such as acetaminophen or ibuprofen. Adults can also take aspirin, but children with fevers should not take aspirin. It is also important to drink enough liquids, to prevent dehydration.

Viral hemorrhagic fevers (VHFs) are a group of illnesses caused by four families of viruses. These include the Ebola and Marburg, Lassa fever, and yellow fever viruses. VHFs have common features: they affect many organs, they damage the blood vessels, and they affect the body's ability to regulate itself. Some VHFs cause mild disease, but some, like Ebola or Marburg, cause severe disease and death.

VHFs are found around the world. Specific diseases are usually limited to areas where the animals that carry them live. For example, Lassa fever is limited to rural areas of West Africa where rats and mice carry the virus.

The risk for travelers is low, but you should avoid visiting areas where there are disease outbreaks. Because there are no effective treatments for some of these viral infections, there is concern about their use in bioterrorism.

Centers for Disease Control and Prevention

Strep is short for Streptococcus, a type of bacteria. There are several types. Two of them cause most of the strep infections in people: group A and group B.

Group A strep causes:

• Strep throat - a sore, red throat. Your tonsils may be swollen and have white spots on them.
• Scarlet fever - an illness that follows strep throat. It causes a red rash on the body.
• Impetigo - a skin infection
• Toxic shock syndrome
• Cellulitis and necrotizing fasciitis (flesh-eating disease)

Group B strep can cause blood infections, pneumonia and meningitis in newborns. A screening test during pregnancy can tell if you have it. If you do, intravenous (IV) antibiotics during labor can save your baby's life. Adults can also get group B strep infections, especially if they are 65 or older or already have health problems. Strep B can cause urinary tract infections, blood infections, skin infections and pneumonia in adults.

Antibiotics are used to treat strep infections.

Ticks are small parasites. They may look like insects, but they have eight legs and are related to spiders. Ticks feed on the blood of people and warm-blooded animals. There are many types of ticks in the United States, and they live in different parts of the country.

Ticks can be different colors and sizes. They can be light-colored, reddish brown, or dark brown. Some ticks are so small that they can be difficult to see. Ticks may get on you if you walk though areas where they live, such as tall grass, leaf litter or shrubs.

If you spend time outdoors or have pets that go outdoors, you need to beware of ticks. When they bite, certain types of ticks can pass on germs that cause different diseases. Sometimes the symptoms can be mild. In other cases, you can have serious, long-lasting health problems. Some of the diseases you can get from a tick bite (called tickborne diseases) include:

• Lyme disease
• Alpha-gal syndrome (tick bite red meat allergy)
• Babesiosis
• Ehrlichiosis
• Rocky Mountain spotted fever
• Tularemia

You may not feel it when a tick bites you. The tick can stay attached to your body for several days. If that tick is infected, it can pass along any germs to you once it starts sucking your blood. But if you catch it and remove it before it has filled up on your blood, you are less likely to get infected.

If you find a tick attached to your skin, remove the tick as soon as you can. You could use a tick removal device or a fine-tipped tweezers:

• Using the tweezers, grab the tick as close to your skin as possible.
• Pull upward with steady, even pressure. Don't twist or jerk the tick. You want to remove the whole tick in one piece if you can. If the mouth-parts of the tick break off and stay in the skin, try to remove them. But if you can't remove them easily, then leave them.
• Thoroughly clean the bite area and your hands with rubbing alcohol or soap and water.

Many tickborne diseases can have similar signs and symptoms. The most common are:

• Fever
• Chills
• Aches and pains
• Rash

If you develop any of these symptoms within several weeks of removing a tick, contact your provider.

There are steps you can take to prevent tick bites:

• Avoid wooded, brushy, and grassy areas, especially during warmer months.
• Wear insect repellent with DEET, picaridin or another U.S. Environmental Protection Agency (EPA)-registered insect repellent.
• Wear light-colored protective clothing.
• Treat your clothing and gear with products containing 0.5% permethrin.
• Tuck your pant legs into your socks and your shirt into your pants.
• Remove your clothing after being outdoors. Check your clothing for ticks and remove any ticks that you find. Wash and dry your clothes at high temperatures.
• Check yourself, your children, and your pets daily for ticks and carefully remove any ticks you find.

Dengue is a viral infection. It can be caused by four related viruses. You can get it if an infected mosquito bites you. It is common in warm, wet areas of the world. Although rare, it can be found in some parts of the United States. Outbreaks are more common during rainy seasons.

Dengue spreads to people through the bite of an infected mosquito. It does not spread directly from person to person. However, a pregnant person can pass the infection on to the baby. In rare cases, it can spread through a blood transfusion, organ transplant, or needle stick injury (an accidental injury from a used needle)..

About one in four people infected with dengue will get sick. For those who do get sick, the infection can be mild or severe. The symptoms of dengue include:

• A high fever
• Nausea and vomiting
• Rash
• Aches and pains (eye pain, usually behind the eyes, and pain in the muscles, joints, or bones)

The symptoms usually last two to seven days.

Severe dengue is a serious form of the illness. About 1 in 20 people who get sick with dengue will develop severe dengue. It can cause shock, internal bleeding, and even death. People are more likely to develop severe dengue if they have had dengue before, are pregnant, or are infants.

Watch for signs and symptoms of severe dengue. Warning signs usually begin about 24 - 48 hours after your fever has gone away. If you or your family member have these signs, get immediate medical care:

• Severe abdominal (belly) pain and tenderness
• Vomiting at least 3 times in 24 hours
• Bleeding from the nose or gums
• Vomiting blood, or blood in the stool (poop)
• Feeling tired, restless, or irritable

There is a blood test which can show if you have been infected with dengue.

There is no specific medicine to treat dengue. Most people will get better after about a week. But if you think you might have dengue:

• See a health care provider and mention any recent travel.
• Rest as much as possible.
• Take acetaminophen to control fever and relieve pain. But do not take aspirin or ibuprofen.
• Drink plenty of fluids to prevent dehydration.

Severe dengue often requires care at a hospital.

In the United States, a dengue vaccine is approved for children who are ages 9 - 16. They must also have previously had dengue and live in areas where dengue is common.

You can also help prevent dengue by avoiding mosquito bites:

• Wear insect repellent with DEET or another U.S. Environmental Protection Agency (EPA)-registered insect repellent. Make sure to follow the instructions for using the repellant.
• Wear clothes that cover your arms, legs and feet.
• Close unscreened doors and windows.

Centers for Disease Control and Prevention

Each spring, summer, and fall, trees, weeds, and grasses release tiny pollen grains into the air. Some of the pollen ends up in your nose and throat. This can trigger a type of allergy called hay fever.

Symptoms can include:

• Sneezing, often with a runny or clogged nose
• Coughing and postnasal drip
• Itching eyes, nose and throat
• Red and watery eyes
• Dark circles under the eyes

Your health care provider may diagnose hay fever based on a physical exam and your symptoms. Sometimes skin or blood tests are used. Taking medicines and using nasal sprays can relieve symptoms. You can also rinse out your nose, but be sure to use distilled or sterilized water with saline. Allergy shots can help make you less sensitive to pollen and provide long-term relief.

Valley Fever is a disease caused by a fungus (or mold) called Coccidioides. The fungi live in the soil of dry areas like the southwestern U.S. You get it from inhaling the spores of the fungus. The infection cannot spread from person to person.

Anyone can get Valley Fever. But it's most common among older adults, especially those 60 and older. People who have recently moved to an area where it occurs are at highest risk for infection. Other people at higher risk include:

• Workers in jobs that expose them to soil dust. These include construction workers, agricultural workers, and military forces doing field training.
• African Americans and Asians
• Women in their third trimester of pregnancy
• People with weak immune systems

Valley Fever is often mild, with no symptoms. If you have symptoms, they may include a flu-like illness, with fever, cough, headache, rash, and muscle aches. Most people get better within several weeks or months. A small number of people may develop a chronic lung or widespread infection.

Valley Fever is diagnosed by testing your blood, other body fluids, or tissues. Many people with the acute infection get better without treatment. In some cases, doctors may prescribe antifungal drugs for acute infections. Severe infections require antifungal drugs.

Centers for Disease Control and Prevention

Salmonella is the name of a group of bacteria. In the United States, it is a common cause of foodborne illness. Salmonella occurs in raw poultry, eggs, beef, and sometimes on unwashed fruit and vegetables. You also can get infected after handling pets, especially reptiles like snakes, turtles, and lizards.

Symptoms include:

• Fever
• Diarrhea
• Abdominal cramps
• Headache
• Possible nausea, vomiting, and loss of appetite

Symptoms usually last 4-7 days. Your health care provider diagnoses the infection with a stool test. Most people get better without treatment. Infection can be more serious in older adults, infants, and people with chronic health problems. If Salmonella gets into the bloodstream, it can be serious. The usual treatment is antibiotics.

Typhoid fever, a more serious disease caused by Salmonella, is not common in the United States. It frequently occurs in developing countries.

NIH: National Institute of Allergy and Infectious Diseases

Ebola, also known as Ebola virus disease (EVD), is a type of hemorrhagic fever. It is a rare and often deadly disease. It can be caused by several different types of Ebola viruses. There are occasional outbreaks of Ebola, and they mostly occur in Africa.

Researchers believe that the virus first spreads from an infected animal to a human. Ebola can then spread from human to human through direct contact with:

• Blood or body fluids of a person who is sick with or has died from Ebola.
• Objects (such as clothes, bedding, needles, and medical equipment) contaminated with body fluids from a person who is sick with or has died from Ebola.
• Semen (through oral, vaginal, or anal sex) from a man who has recovered from Ebola. The virus can remain in semen and other body fluids, even if the person no longer has symptoms.

When people become infected with Ebola, they do not start developing signs or symptoms right away. They cannot spread Ebola to others until after they develop symptoms.

The symptoms of Ebola may appear anywhere from 2 to 21 days after exposure to the virus. The average is about 8 to 10 days. The symptoms usually include:

• Fever
• Headache
• Joint and muscle aches
• Weakness and fatigue
• Sore throat
• Gastrointestinal symptoms including abdominal (belly) pain, diarrhea, and vomiting
• Loss of appetite
• Unexplained bleeding or bruising

Other symptoms may include a rash, red eyes, and hiccups.

The early symptoms of Ebola are similar to other more common diseases. This makes it difficult to diagnose Ebola in someone who has been infected for only a few days. If a person has the symptoms of Ebola and may have been exposed to the virus, the health care provider can do a blood test for Ebola. It can take a few days after the symptoms start before Ebola shows up in the blood test.

In the United States, there are two approved medicines to treat Ebola that is caused by one specific type of virus (Zaire ebolavirus). These medicines have not been evaluated to treat Ebola caused by other types of Ebola viruses. The medicines are monoclonal antibodies, which are immune system proteins that are created in the lab.

Whether or not there are medicines to treat a case of Ebola, there is supportive care. This type of care can improve the chances of survival, especially when given early. Supportive care includes:

• Giving fluids and electrolytes
• Giving medicines to support blood pressure, reduce vomiting and diarrhea, and to manage fever and pain
• Giving oxygen
• Treating any other complications or infections

People who recover may still have side effects afterwards, such as fatigue, muscle aches, eye and vision problems, and stomach pain.

In the United States, there is one vaccine that has been approved to prevent Ebola caused by one specific type of Ebola virus (Zaire ebolavirus). It may be given to health care providers who will be or may be treating Ebola patients and people who work with live Ebola virus in labs.

If you live in or plan to travel to a region where Ebola virus may be present, you can help protect yourself by avoiding contact with:

• Blood and body fluids of people who are sick
• Semen from a man who has recovered from Ebola, until testing shows that the virus is gone from his semen
• Items that could be contaminated with blood or body fluids from someone who has Ebola
• Bats, forest antelopes, and nonhuman primates (such as monkeys and chimpanzees), including their blood, fluids, or meat

Centers for Disease Control and Prevention

Bacteria are living things that have only one cell. Under a microscope, they look like balls, rods, or spirals. They are so small that a line of 1,000 could fit across a pencil eraser. Most types of don't make you sick. Many types are helpful. Some of them help to digest food, destroy disease-causing cells, and give the body needed vitamins. Bacteria are also used in making healthy foods like yogurt and cheese.

But infectious bacteria can make you ill. They reproduce quickly in your body. Many give off chemicals called toxins, which can damage tissue and make you sick. Examples of bacteria that cause infections include Streptococcus, Staphylococcus, and E. coli.

Antibiotics are the usual treatment. When you take antibiotics, follow the directions carefully. Each time you take antibiotics, you increase the chances that bacteria in your body will learn to resist them causing antibiotic resistance. Later, you could get or spread an infection that those antibiotics cannot cure.

NIH: National Institute of Allergy and Infectious Diseases