Plenty of pesky germs plague people during the winter months. Blame cold- and flu-causing viruses that thrive when people spend more time indoors together. But colds and flu aren't the only cold-weather health problems that bug people when the temperature drops. Here are six to watch out for:

Heart problems

During the winter, the number of heart attacks climbs, according to the American Heart Association (AHA).

One culprit: Physical exertion — think shoveling snow — in chilly temperatures could put a strain on the heart, especially in people who aren’t usually physically active or who have an existing heart condition. Indeed, people with heart disease tend to experience chest pain and discomfort, also called angina, when the mercury drops, reports the AHA.

“People who aren’t active don’t realize how much physical exertion it takes to clear up a sidewalk,” said Dr. Derek R. Cooney, who specializes in emergency medicine at SUNY Upstate Medical University.

For safer shoveling, the AHA recommends taking frequent rest breaks while shoveling to avoid overworking the heart. Don’t eat a heavy meal before shoveling either as that can put an extra load on the heart. Also, use a small shovel to avoid lifting heavy mounds of snow.

Seasonal affective disorder

As the days get shorter, some people develop the winter blues. Seasonal Affective Disorder, or SAD, is a form of depression that can occur throughout the year, but the most common type appears in late fall or early winter and lasts until summer. Between 4 and 6 percent of Americans suffer from SAD, which is more common in women, according to the American Academy of Family Physicians.

Not everyone who develops SAD experiences the same symptoms, but hallmark signs include feelings of sadness, anxiety, hopelessness, guilt or worthlessness; thoughts of suicide; fatigue; and irritability. The cause of SAD is unknown. Some experts believe the condition could be linked to an imbalance of chemicals in the brain that regulate sleep, energy and mood. This imbalance occurs when levels of melatonin, one of these brain chemicals, rise while levels of serotonin, the other chemical, drops.

According to the American Psychiatric Association, getting more sunlight can improve symptoms of SAD. Experts also recommend talk therapy and antidepressants. For people with severe SAD, light box therapy may be advised. Treatment involves sitting in front of a special lamp that mimics outdoor light, without looking directly into the light, for about 30 minutes a day. Experts recommend starting light therapy in the early fall and continuing until the spring. The light is used to adjust daily sleep cycles (circadian rhythm), which may play a role in mood.  Although light therapy has been shown to ease depression, it won’t cure SAD.

Carbon monoxide poisoning

Each year, more than 400 Americans die from unintentional carbon monoxide poisoning, according to the Centers for Disease Control and Prevention (CDC). Another 20,000 Americans visit the emergency room and more than 4,000 are hospitalized annually.

Carbon monoxide (CO) is a colorless and odorless gas that is produced by burning fuel. Any fuel-burning appliances in the home could be a source of CO, including stoves, gas ranges and heating systems. Running a car or generator in an attached garage of a home can also cause CO poisoning.

Common symptoms of CO exposure are headache, fatigue, nausea, dizziness and confusion. But CO poisoning can be difficult to diagnose because symptoms mimic those of other illnesses. If more than one person develops the aforementioned symptoms over a short period of time, experts say that could be a sign that something is wrong.

Installing a CO detector in the house that will sound an alarm if high levels of CO are present is essential. To prevent CO from becoming a problem, the CDC advises against using a range or oven to heat a home. Never leave the car motor running in the garage and never run a generator or any gas-powered engine in the basement or any other enclosed space in the home.

Frostbite

Frostbite occurs when the skin and the tissue underneath it freeze. It often affects areas of the body that are more exposed to the cold such as the nose, ears, cheeks, chin, fingers, or toes and have less circulation. Frostbite can permanently damage skin and underlying tissue, and severe cases may require amputation.

“Symptoms often begin with pain and a blotchy white appearance,” said Dr. Jeffrey Sankoff, an emergency medicine physician at the Denver Health Medical Center. “Once sensation is lost and the area it stops being painful, frostbite is severe.”

Get out of the cold if frostbite is suspected, Sankoff advised. “Once inside, don’t rub the frostbite since that can cause even more damage,” he said. Don't apply direct heat, such as hot water, to the area either, he added, as that can burn already-damaged skin and tissue.

Instead, immerse the affected area in room-temperature water. “It can be quite painful, but do it till the area warms up,” Sankoff said. Seek medical attention if the frostbitten area starts to blister or turns black.

“The best way to prevent frostbite is to plan and prepare,” Sankoff said. “Dress properly and remember that layers are important. They can be removed and replaced as needed.”

 Hypothermia

Hypothermia, which can affect the ability to think or move, occurs when a person’s body temperature drops below 95 degrees. This happens when someone is exposed to cold temperatures for a long period of time. But hypothermia can happen at higher temperatures, too.

“We occasionally see cases during the summer,” Sankoff said. “Any temperature lower than body temperature can cool the body. While there is no absolute threshold, it is far more common once the temperature drops below 45 degrees or so.”

Babies and the elderly are especially at risk as are people who drink alcohol. Even one drink is enough to disrupt the body’s ability to regulate its temperature, according to Sankoff. “Once a person becomes intoxicated, that risk becomes truly heightened, but the risk varies by individual,” he said.

“People who drink alcohol may feel warm even though they’re cold,” Cooney said. “But after a time the warm feeling goes away, which is dangerous if someone is outside for long periods of time.”

During the early stages of hypothermia, a person may feel tired, confused and disoriented and experience uncontrollable shivering. Eventually, a person stops shivering, doesn't feel cold at all, develops blue skin and dilated pupils and loses consciousness.

Experts recommend getting medical attention during the early stages of hypothermia, before later symptoms make it difficult to seek help.  “The best way to treat people with hypothermia is to re-warm them,” Sankoff said. “If it’s mild, we just let people re-warm themselves by putting blankets on them until they warm up again.” If it's more severe, he said a person is treated with warming lights, blankets and warm fluids given through an IV.

Shoveling injuries

Some people dread shoveling snow, and for good reason.  It can be hazardous to health. According to a 2011 study published in the American Journal of Emergency Medicine, an average of more than 11,000 adults and children are hospitalized for shoveling injuries every year. The most common injuries include heart problems, head injuries, muscle sprains, cuts and fractures and, especially, the lower back.

To avoid falling on snow or ice, experts recommend wearing shoes or boots with traction. To prevent back injuries, push the snow with the shovel, rather than lifting it. If lifting is unavoidable, scoop up a small amount of snow, then squat, keeping legs apart, knees bent, and back straight. Then, slowly rise but avoid bending at the waist. Experts also caution against throwing snow over the shoulders or to the side, since the twisting motion involved performing these movements stresses the back.

Pass it on: Use common sense to prevent many winter health problems.

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