Infectious Diseases

What is malaria and how can I prevent it?

DEAR DOCTOR K: I am traveling abroad in a few weeks. My travel clinic has prescribed antimalarial medication. Can you tell me more about malaria and how to prevent it?

DEAR READER: Malaria is a serious disease caused by the Plasmodium parasite. The parasite is not found today in the United States or Canada, but it is common in areas to which North Americans travel: Africa, Asia, and Central and South America. The U.S. Centers for Disease Control and Prevention estimate that there are over 200 million new cases of malaria each year around the world.

What is fifth disease and is it contagious?

DEAR DOCTOR K: A child in my son's class has "fifth disease." What is this? Is it contagious? What can I do to prevent my son from catching it?

DEAR READER: Fifth disease, also known as erythema infectiosum, is a common viral infection among school-aged children. It is caused by a virus called parvovirus B19. Fifth disease usually is a mild illness. Some people who are infected with the virus may never realize they have it. When symptoms do occur, they may include a stuffy nose, runny nose, slight fever, or body aches, headache, nausea, diarrhea and fatigue. These symptoms pass after three or four days.

What is MRSA and why is it so dangerous?

DEAR DOCTOR K: What is MRSA? What makes it so dangerous?

DEAR READER: We have a brain, and bacteria don't. So you'd think bacteria wouldn't be able to outsmart us. But they sure can figure out ways to become resistant to the antibiotics we use to kill them. In the early days of antibiotics, 70 years ago, one of the most common and dangerous types of bacteria -- Staphylococcus aureus -- could be killed by penicillin.

Is there a treatment or vaccine being created for Ebola?

DEAR DOCTOR K: Like everyone, I'm afraid that the Ebola virus could spread in the United States. There must be research underway to find treatments, and vaccines to prevent it in the first place. Please tell me there is.

DEAR READER: Infection with the Ebola virus is indeed frightening. In West Africa, the site of the latest outbreak of Ebola, more than half the people who have become infected with it have died. I doubt there will be an epidemic of Ebola in the U.S. and other developed nations, but there have been cases, and there will be more.

Can you still have symptoms of Lyme disease after you’ve completed your treatment?

DEAR DOCTOR K: My neighbor was diagnosed with Lyme disease. Why does he still have symptoms, even though he has completed his treatment?

DEAR READER: The great majority of people diagnosed with Lyme disease, and properly treated, are cured. However, there are some people like your neighbor, who are never fully cured, and we do not understand why proper diagnosis and treatment does not always lead to the elimination of suffering. Here's what we do know. Lyme disease is an infection caused by bacteria that are transmitted through tick bites.

What is mononucleosis– why is it called the “kissing disease”?

DEAR DOCTOR K: What is mononucleosis, and why is it called the "kissing disease"?

DEAR READER: Mononucleosis, or "mono," is an illness caused by several viruses, primarily the Epstein-Barr virus (EBV). Mono was nicknamed the "kissing disease" because EBV commonly is transmitted during kissing. The virus lives in different parts of the body, including the throat. The virus can leave throat cells and enter the saliva. Most viruses that infect us enter our body, maybe cause temporary illness, and then get killed by the immune system.

What is a virus — what makes viral illnesses so difficult to treat?

DEAR DOCTOR K: What is a virus? And what makes viral illnesses so difficult to treat?

DEAR READER: Viruses are a very simple kind of germ. They are smaller and simpler than other common germs, such as bacteria and fungi. They cause illnesses ranging from mild -- like the common cold -- to potentially fatal. This includes diseases such as smallpox, influenza, Ebola and HIV.

What is the best way to remove a tick from your skin?

DEAR DOCTOR K: I live in a heavily wooded area, so I'd like to know the best way to remove a tick if you spot one on your skin.

DEAR READER: Knowing how to remove a tick is a useful skill for anyone who spends time outdoors, or who cares for someone who does. The sooner a tick is removed -- correctly -- the less likely the critter can deliver bacteria that cause Lyme disease or other tick-borne diseases.

Should I be worried about the new kind of “bird flu” discovered in China?

DEAR DOCTOR K: I heard that a dangerous new kind of "bird flu" was recently discovered in China. Should we in the United States be worried?

DEAR READER: You're right: In March 2013, cases of a brand-new kind of bird flu were discovered in China. One of the hardest things to predict is what will happen when a new strain of the influenza ("flu") virus first infects humans. I'm not exaggerating when I say it could turn out to pose no threat at all in the U.S., or it could be truly terrible.

What is C. diff infection?

DEAR DOCTOR K: I've heard that an illness known as "C. diff" is running rampant in hospitals. What is it? How can I avoid it during my upcoming hospitalization?

DEAR READER: You're referring to a dangerous intestinal infection caused by a bacterium known as Clostridium difficile, or "C. diff." C. diff bacteria, and the spores they produce, are not just in hospitals; they're everywhere. And they're not just in the environment around us; they're also inside many of us, in our intestines, along with trillions of other bacteria.