Cold Temperature Exposure

It's easy to get cold quickly if you are outside in wet, windy, or cold weather. Cold temperature exposure can also happen if you spend time in a dwelling or other building that is not well-heated during cold weather.

Injuries from cold exposure:

* "Frost nip" usually affects skin on the face, ears, or fingertips. Frost nip may cause numbness or blue-white skin color for a short time, but normal feeling and color return quickly when you get warm. No permanent tissue damage occurs.
* Frostbite is freezing of the skin and the tissues under the skin because of temperatures below freezing. Frostbitten skin looks pale or blue and feels cold, numb, and stiff or rubbery to the touch.
* Cold injuries, such as trench foot or chilblains, may cause pale and blistered skin like frostbite after the skin has warmed. These injuries occur from spending too much time in cold, but not freezing, temperatures. The skin does not actually freeze.
* An abnormally low body temperature (hypothermia) occurs when the body loses heat faster than it can make heat. Early symptoms of hypothermia include shivering in adults and older children, clumsy movements, apathy (lack of concern), poor judgment, and cold, pale, or blue-gray skin. Hypothermia is an emergency condition—it can quickly lead to unconsciousness and death if the heat loss is not stopped.

Risk factors for cold exposure injury:

There are many factors that increase your risk of injury from exposure to cold temperatures.

* Being a baby
* Being an older adult
* Drinking alcohol
* Being in outdoor conditions, such as high altitudes or windy, wet weather, or being immersed in cold water
* Not being dressed properly, having wet skin, or wearing wet clothing
* Being tired or dehydrated
* Being exposed to cold temperatures in your workplace, such as working in cold-storage units
* Having certain health risks

Many people get cold hands or feet, which often are bothersome but not a serious health problem.

You are more likely to feel cold easily if you:

* Do not have much body fat. Fat under the skin helps keep you warm. People who have low body fat may be more likely to get hypothermia. Babies, older or ill adults, or malnourished people have low body fat.
* Smoke cigarettes or drink caffeine. Nicotine (from tobacco) and caffeine cause narrowing of the blood vessels in the hands and feet. When blood vessels are narrowed, less blood flows to these areas, causing the hands and feet to feel cold.
* Are under a lot of stress or feel tired. Chronic stress or anxiety can cause your nervous system to release adrenaline, which acts to narrow the blood vessels that supply blood to the hands and feet.
* Have a medical condition, such as hypothyroidism or Raynard's phenomenon, that makes you feel or react more strongly to cold temperatures.

Infection - What Happens

There are two types of HIV:

* HIV-1, which causes almost all the cases of AIDS worldwide
* HIV-2, which causes an AIDS-like illness. HIV-2 infection is uncommon in the United States.

How the disease is spread:

HIV is spread when blood, semen, or vaginal fluids from an infected person enter another person's body, usually through:

* Sexual contact. The virus may enter the body through a tear in the lining of the rectum, vagina, urethra, or mouth. Between 75% and 80% of all cases of HIV are transmitted by sexual contact.
* Infected blood. HIV can be spread when a person:
o Shares needles, syringes, cookers, cotton, cocaine spoons, or eyedroppers used for injecting drugs or steroids.
o Is accidentally stuck with a needle or other sharp item that is contaminated with HIV.

It is now extremely rare in the United States for HIV to be transmitted by blood transfusions or organ transplants. Blood and organ donors are screened for risk factors. All donated blood and organs are screened for HIV.

Health care workers are no longer considered to be at high risk of exposure to HIV. Policies are in place in health facilities that require protection from accidental exposure. Workers must properly dispose of sharp objects and wear protective gloves, gowns, and eye and face protection. These measures have been effective in protecting health care workers from HIV.

Spread of HIV to babies:

A woman who is infected with HIV can spread the virus to her baby during pregnancy, delivery, or breast-feeding.

* Most children younger than 13 years who have HIV were infected with the virus by their mothers.
* The risk of a woman spreading HIV to her baby can be greatly reduced if she is on medicine that reduces her viral load (HIV RNA) to undetectable levels during pregnancy, if she receives AZT (ZDV) before the baby is born, and if she does not breast-feed her baby. The baby should also receive treatment after it is born.

Ways HIV cannot be spread:

HIV does not survive well outside the body. Therefore, HIV cannot be spread through casual contact—such as sharing drinking glasses or by casual kissing—with an infected person. HIV is not transmitted through contact with an infected person's saliva, sweat, tears, urine, or feces, or through insect bites.

Contagious and incubation period:

The incubation period—the time between when a person is first infected with HIV and when early symptoms develop—may be a few days to several weeks.

It can take as little as 2 weeks or as long as 6 months from the time you become infected with HIV for the antibodies to be detected in your blood. This is commonly called the "window period," or seroconversion period. During the window period, you are contagious and can spread the virus to others. If you think you have been infected with HIV but you test negative for it, you should be tested again 6 months later.

After you become infected with HIV, your blood, semen, or vaginal fluids are always infectious, even if you receive treatment for the HIV infection.

Stages of HIV:

Most people go through the following stages after being infected with HIV if the infection is not treated:

* Acute retro viral syndrome, which has symptoms similar to mononucleosis. This often develops within a few days of infection, but may occur several weeks after the person is infected.
* HIV without symptoms (asymptomatic). It may take years for HIV symptoms to develop. But even though no symptoms are present, the virus is multiplying (or making copies of itself) in the body during this time. HIV multiplies so quickly that the immune system cannot destroy the virus. After years of fighting HIV, the immune system starts to weaken.
* HIV with symptoms (symptomatic). After your immune system starts to weaken, you are more likely to develop certain infections or illnesses, such as some types of pneumonia or cancer that are more common in people who have a weakened immune system.
* AIDS, which occurs during the last stage of infection with HIV. If HIV goes untreated, AIDS develops in most people within 12 to 13 years after the initial infection. With treatment for HIV, the progression to AIDS may be delayed or prevented.

A small number of people who are infected with HIV are rapid progressors. They develop AIDS within a few years if they do not receive treatment. It is not known why the infection progresses faster in these people.

Nonprogrammable and HIV-resistant:

A few people have HIV that does not progress to more severe symptoms or disease. They are referred to as nonprogrammer.

A small number of people never become infected with HIV despite years of exposure to the virus. For example, they may have repeated, unprotected sex with an infected person. These people are said to be HIV-resistant.

Heat-Related Illnesses

A healthy body temperature is maintained by the nervous system. As the body temperature increases, the body tries to maintain its normal temperature by transferring heat. Sweating and blood flow to the skin (thermo regulation) help us keep our bodies cool. A heat-related illness occurs when our bodies can no longer transfer enough heat to keep us cool.

A high body temperature (hypothermia) can develop rapidly in extremely hot environments, such as when a child is left in a car in the summer heat. Hot temperatures can also build up in small spaces where the ventilation is poor, such as attics or boiler rooms. People working in these environments may quickly develop hypothermia.

High temperature caused by a fever is different from a high body temperature caused by a heat-related illness. A fever is the body's normal reaction to infection and other conditions, both minor and serious. Heat-related illnesses produce a high body temperature because the body cannot transfer heat effectively or because external heat gain is excessive.

Heat-related illnesses include:

* Heat rash (prickly heat), which occurs when the sweat ducts to the skin become blocked or swell, and cause discomfort and itching.
* Heat cramps, which occur in muscles after exercise because sweating causes the body to lose water, salt, and minerals (electrolytes).
* Heat edema (swelling) in the legs and hands, which can occur when you sit or stand for a long time in a hot environment.
* Heat tetanus (hyperventilation and heat stress), which is usually caused by short periods of stress in a hot environment.
* Heat syncope (fainting), which occurs from low blood pressure when heat causes the blood vessels to expand (dilate) and body fluids move into the legs because of gravity.
* Heat exhaustion (heat prostration), which generally develops when a person is working or exercising in hot weather and does not drink enough liquids to replace those lost liquids.
* Heatstroke (sunstroke), which occurs when the body fails to regulate its own temperature and body temperature continues to rise, often to 105°F (40.6°C) or higher. Heatstroke is a medical emergency. Even with immediate treatment, it can be life-threatening or cause serious long-term problems.

Often, environmental and physical conditions can make it difficult to stay cool. Heat-related illness is often caused or made worse by dehydration and fatigue. Exercising during hot weather, working outdoors, and overdressing for the environment increase your risk. Caffeine or alcohol also increase your risk for dehydration.

Many medicines increase your risk of a heat-related illness. Some medicines decrease the amount of blood pumped by the heart (cardiac output) and limit blood flow to the skin, so your body is less able to cool itself by sweating. Other medicines can alter your sense of thirst or increase your body's production of heat. If you take medicines regularly, ask your doctor for advice about hot-weather activity and your risk of getting a heat-related illness.

Other things that may increase your risk of a heat-related illness include:

* Age. Babies do not lose heat quickly and they do not sweat effectively. Older adults do not sweat easily and usually have other health conditions that affect their ability to lose heat.
* Obesity. People who are overweight have decreased blood flow to the skin, hold heat in because of the insulating layer of fat tissue, and have a greater body mass to cool.
* Summer heat waves. People who live in cities are especially vulnerable to illness during a summer heat wave because heat is trapped by tall buildings and air pollutants, especially if there is a high level of humidity.
* Chronic diseases, such as diabetes, heart failure, and cancer. These conditions change the way the body gets rid of heat.
* Travel to wilderness areas or foreign countries with high outdoor temperatures and humidity. When you go to a different climate, your body must get used to the differences (acclimate) to keep your body temperature in a normal range.

Most heat-related illnesses can be prevented by keeping the body cool and by avoiding dehydration in hot environments. Home treatment is usually all that is needed to treat mild heat-related illnesses. Heat exhaustion and heatstroke need immediate medical treatment.