Most people blame viruses or bacteria when they get an infection. But there's another—often-overlooked—possibility, that is fungi. Fungal infection is more common than most people realize.

Example: Candida, a fungus that causes yeast infections, is the fourth most common microorganism found in the blood of hospitalized patients. Candida can infect the mouth, causing white, painful patches on the tongue and inside the cheeks (thrush). In the hospital or during serious illnesses, these mild fungal infections can develop into potentially fatal ones, which can affect the heart or brain.

Fungi are normally present on the skin and in the intestinal tract. Local fungal infections, such as athlete's foot, are common and relatively easy to treat. Mild infections also can occur in the other places that fungi normally inhabit, such as the vagina, mouth, groin area or in fingernails or toenails.

It's rare for someone who's healthy to get a serious fungal infection. Those at greatest risk include people with compromised immune systems, such as hospitalized patients and individuals with diabetes, lung disease, kidney failure, cancer, human immuno-deficiency virus (HIV) or some other chronic well as anyone who has undergone an organ or bone-marrow transplant.

To learn more, John R. Perfect, MD, a renowned specialist in fungal infections answered the following questions…

How difficult is it to diagnose a fungal infection?

Infections of the skin usually can be diagnosed just by looking at them. Dermatophytosis (ringworm), for example, usually appears as scaly, red ring-shaped patches. Systemic infections that have spread into several organs) usually require taking a sample of body fluid, such as sputum from the lungs or blood, and culturing it in a laboratory and/or examining specimens under a microscope for fungal forms.

Caution: Fungal infection in the lungs can be mistaken for cancer on an X-ray. The only way to distinguish the two is by taking a biopsy.

Are fungal infections contagious?

Some fungal infections of the skin, such as ringworm, can be passed from one person to another by sharing towels or clothing or having direct contact with a rash. Most other fungal infections occur when microscopic spores in the air come in contact with the skin or are inhaled. Many fungi reproduce and spread through these microscopic spores.

Is there any way to protect yourself from developing a fungal infection?

We live in a virtual sea of fungi," so it is impossible to avoid them. The vast majority cannot cause disease. The best prevention is for your doctor to be aware of these infections and for you to get treatment early if one develops.

Does a skin/nail infection indicate that there's a more serious underlying problem?

Usually not. It's possible that someone with a serious, underlying illness will get a nail or skin fungal infection-but it's unlikely that the infection would be the first sign. The most dangerous fungal infections, such as aspergillosis and cryptococcosis, tend to occur in patients who are already sick and perhaps undergoing extensive medical treatments. Both of these infections primarily affect the lungs but occasionally spread to other areas of the body.

Someone with cancer or diabetes might be more likely to develop a severe Candida infection because he/she may be in a hospital receiving intravenous antibiotics or chemotherapy, which may allow fungi to proliferate in the body. Although Candida most often causes yeast infections, in more serious cases, it can invade the bloodstream or certain organs.

Some fungal infections may be important warning signs. Therefore, anyone who's getting fungal infections more than twice a year or has an infection that doesn't respond to treatments needs to consider the possibility that his/her immune system isn't working well—and see his doctor right away.

Aren't fungal infections difficult to treat?

Fungi are very hard to kill. Like humans, fungi are eukaryotes (single-celled or multicellular organisms whose cells contain a distinct membrane-bound nucleus). This means that we share the same kinds of "cellular machinery." It's difficult to develop drugs that will kill a fungus without killing human cells at the same time. Fungi grow slowly and protect themselves inside host cells. Despite this, there has been great improvement in the drugs we have for invasive fungal infections. However, some antifungal medications can be costly—up to $250 for a month's treatment.

Latest development: The newest class of antifungal drugs, known as candins, include caspofungin (Cancidas), micafungin (Mycamine) and anidulafungin (Eraxis), which are used to treat aspergillosis and serious Candida infections. These medications inhibit a component that fungi require to create cell walls. Since human cells don't have that component, they aren't affected by these drugs. Because of this, the candins are less likely to cause toxicity and/or side effects than older antifungal agents, such as polyene drugs, including amphotericin B (Fungizone).

Topical antifungal drugs are effective, but they don't necessarily work quickly. It's common for patients with athlete's foot to apply the creams for weeks or months. Treating a nail fungus may require oral antifungal drugs.

What happens if a fungal infection goes untreated?

That depends on the severity of the infection. Mild skin fungal infections sometimes clear up on their own-and even if they don't, they may require minimal treatment. A patient with a nail fungus, for example, might choose to ignore it, since the only symptom—usually yellow, green or brown nail discoloration—is cosmetic.

Athlete's foot, jock itch and vaginal yeast infections, on the other hand, can be itchy and uncomfortable. They respond well to over-the-counter topical agents, such as clotrimazole (Gyne Lotrimin or Mycelex) or miconazole (Monistat).

An invasive fungal infection, which usually begins in the lungs or bloodstream, can spread rapidly to other parts of the body and always requires treatment. The drugs may be given orally or intravenously. In the highest-risk patients, such as those getting chemotherapy, an antifungal drug can be given prophylactically--that is, to prevent an infection from occurring.

The Latest Drug Research

New diabetes drug Januvia blocks an enzyme that suppresses the release of insulin after blood sugar rises—for instance, after a meal, says Carol Levy, MD. This lets the body release insulin longer. Januvia—chemical name sitagliptin phosphate—works like the injected drug exenatide (Byetta), but Januvia is taken by mouth. It is best for people with type 2 diabetes who cannot keep their blood sugar levels low enough with older diabetes medications, such as metformin.

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