Dear Doctors: We live in New Hampshire, and people are worried about Eastern equine encephalitis. There have been several cases, and someone has died. I’ve lived here all my life, and this disease is new to me. Can you please share what is known?

Dear Reader: Eastern equine encephalitis is a rare but potentially fatal mosquito-borne illness. Also known as EEE, it is one of four equine encephalitis viruses. The others are Western and Venezuelan equine encephalitis and West Nile virus. As with the other three, EEE originates in birds and rodents. It is spread to humans through the bite of an infected mosquito.

According to data shared by the Centers for Disease Control and Prevention, there are an average of 12 confirmed cases of EEE in humans in the United States each year. Occasional cases are reported in dogs, deer, horses and other farm animals. However, those animals, as well as humans, are what is known as a “dead-end host.” That means the concentration of EEE virus in the blood is too low to infect a mosquito, and thus cannot be passed on to another human. You also cannot become infected through contact with a sick person. Bottom line -- there is no human-to-human transmission.

As of this writing, there have been 13 confirmed cases of EEE in humans in the U.S. this year. They occurred in seven states, primarily in the Northeast. All 13 people developed severe disease, and two of them died.

Public health officials also track infected mosquitos, and that data has raised concerns. Spurred by a warming climate, the range of the mosquitos that carry the EEE virus is spreading. Infected mosquitos have been found in more than 20 states, primarily in the Northeast and Southeast. No infected mosquitos have been found farther west than Houston.

Not everyone infected with the virus becomes ill. When symptoms do occur, they typically begin four to 10 days after infection. The resulting illness can range from mild to severe. Initial symptoms include high fever, headache, muscle and body aches, joint pain, stiffness in the neck, fatigue and chills. EEE can escalate to cause neurologic disease, which affects the brain and spinal cord. This includes meningitis, which is inflammation of the membranes surrounding the spinal cord and brain, and encephalitis, which is inflammation of the brain Nearly one-third of these types of severe cases are fatal.

Diagnosis is based on the person’s symptoms and their potential recent exposure. When EEE is suspected, blood tests and analysis of spinal fluid will be done. There are no targeted medications for the disease, and treatment focuses on managing symptoms. This can include medications for fever, headache and pain, intravenous fluids and respiratory therapy. At this time, there is no EEE vaccine.

You can lessen the risk of any mosquito-borne illness by removing any sources of standing water around the home, which mosquitos need to lay eggs. Water trapped in a rain gutter or even an abandoned toy can become a breeding ground. And be sure to protect your body. Wear appropriate clothing and use an insect repellent when spending time outdoors.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I would like to know why it is that so many medications have side effects. Is it the medications themselves, or is it the additives that are used in making them? Also, why do some people have severe side effects and others don’t have any at all?

Dear Reader: The answer to your question begins with a concept known as homeostasis. As with many medical terms, it has its roots in Greek: The prefix “homeo” means similar, and the suffix “stasis” means stable. The term was coined in 1926 to describe the dynamic feedback loops that allows the many -- and often competing -- physiological processes that contribute to health to remain in balance. Add in the fact they take place simultaneously, dictated by constant changes inside and outside of the body, and you get a sense of the complexity of it all.

Homeostasis starts at the cellular level. It includes functions such as the maintenance of pH levels and ion concentrations in the fluids inside and surrounding the cells; the manufacture of lipids, hormones and proteins; enzyme balance; the production and distribution of energy; and the safe transport and elimination of waste products. That is a pretty long list, and we’ve only scratched the surface.

If the body detects a potentially harmful imbalance, it sends out instructions with the corrections that are needed. The organs and tissues then respond, with the goal of maintaining homeostasis. These finely calibrated feedback loops oversee functions such as regulation of blood pressure, blood sugar control, oxygen transport, digestion, and nutrient production and absorption. They also are crucial to feelings of hunger and thirst and circadian cycles, and they even play a role in mood and emotion.

A departure from homeostasis can result in discomfort, pain or malfunction. When prolonged, it can lead to disease. But the medications that we take, or the treatments that we undergo, can also have an effect on homeostasis. It is those disruptions that can give rise to side effects. For example, a drug known as hydralazine, which relaxes blood vessels, is effective for the management of hypertension. It is believed to work by affecting calcium ion homeostasis. But the drug can also stimulate the sympathetic nervous system, which can lead to side effects such as dizziness or headache.

Another example is non-steroidal anti-inflammatories, or NSAIDs, which ease pain and inflammation. They work by reducing production of an enzyme the body uses to mount an inflammatory response. But NSAIDs also change the behavior of cells in the stomach that help maintain optimal pH levels, which can lead to tissue damage. This side effect of NSAIDs is caused by an unintended disruption of homeostasis.

How a drug affects someone, including the side effects they may experience, depends on a number of factors. These include the person’s size and weight, age, metabolism, kidney and liver function, activity level, genetic makeup and habits such as smoking or drug use. Genetics plays a role, as well. Bottom line: Our response to medications, and the side effects they may cause, are as varied and individual as the people taking them.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctors: I had such bad abdominal pain that my husband took me to the ER. I was told I was passing a kidney stone. It took two days, and it was excruciating. What are kidney stones? Is there anything I can do to keep this from happening again?

Dear Reader: A kidney stone is a bit of solid debris that can form due to a buildup of salts and minerals within the urinary tract. It can range in size from a grain of sand to a small -- or not-so-small -- pebble. It is estimated that 1 in 10 people will pass a kidney stone during their lifetime. Although this can occur at any age, it is most common in people age 30 and older.

As you have discovered (unfortunately!), passing a kidney stone is often very painful. This is because the stone can become stuck on its journey to exit the body. When stones leave the kidney, they pass into the ureter, which is the tube through which urine moves to the bladder. The walls of the ureter are not elastic, and thus cannot yield to a foreign object. When a kidney stone gets stuck, it can cause the ureter to go into spasm, which can cause significant pain.

When a kidney stone is unable to move, the resulting blockage forces urine to back up into the kidney. This leads to mounting pressure that causes widespread pain in the region of the belly, groin and back. Blockages can also lead to infection.

Symptoms include fever, nausea, vomiting, urine that is cloudy or has an unpleasant odor, urinary urgency and blood in the urine. Treatment begins with the use of medications to manage pain, plus hydration to help pass the stones. Larger stones and those that are impacted may require shockwave therapy. This breaks the stone into particles that are small enough to move through the ureter. In very difficult cases, surgical options may be considered.

Anyone who has passed a kidney stone, or knows of someone who has, will be motived to make lifestyle changes to decrease their risks. The first step is to drink plenty of water. This prevents the urine from becoming concentrated, which leads to development of the crystals from which kidney stones are formed. It is also important to pay attention to diet. This is particularly true for someone who has already passed a kidney stone.

Kidney stones fall into several categories. The most common are made up of calcium and oxalate, a natural compound found in vegetables, fruits, nuts and grains. Foods high in oxalate include spinach, walnuts, beets, sweet potatoes, chocolate and tea. It is also important to limit foods high in purines. These contribute to the formation of uric acid, which is associated with the formation of another type of kidney stone. Foods high in purines include red meat, organ meats and shellfish. Alcohol consumption also plays a role in the formation of kidney stones. Your health care provider can help you with the lifestyle changes needed to decrease your risk of kidney stones.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10960 Wilshire Blvd., Suite 1955, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)