Hello, dear readers, and welcome back to our monthly letters column. We're getting closer to autumn, but in much of the country, heat waves continue. Please be sure to take precautions. Drink enough water throughout the day to fuel your body's natural cooling system, which is sweating. When possible, stay indoors during the hottest hours. And, if needed, take shelter in public places in your area with air conditioning, such as malls, community centers, libraries or local cooling centers. Even a short break in a cooler environment can be helpful. And now, onward to the mail:

-- We recently wrote about spinal stenosis, which is when the spaces and hollows of the spinal column begin to narrow. The resulting pressure on the spinal cord and nerve roots causes symptoms that include pain, burning, numbness and weakness in the back, legs or feet. That prompted a question from a reader who developed these symptoms. "I had an MRI two years ago, and it showed some spinal stenosis and a mild protrusion on the disc," he wrote. "I developed numbness in my left leg and tingling in both feet, but no buttock or thigh pain. Two chiropractors and a physical therapist have offered conflicting advice, and none of their suggestions seem to work. What kind of specialist should I see?"

You would be best served by seeing a spine specialist, either a neurosurgeon or an orthopedic surgeon. A disc protrusion, if mild, can be treated with physical therapy and anti-inflammatories. It can sometimes require an epidural steroid injection. Some people with spinal stenosis are helped by a minimally invasive procedure called Vertiflex, which uses a small implant to lessen pressure within the spine to ease symptoms.

-- We recently discussed a sensitive and accurate blood test known as A1C, which measures someone's average blood sugar levels over the previous eight- or 12-week period. It is used to diagnose Type 2 diabetes. This is a condition in which the body stops responding properly to insulin, which leads to chronic high blood sugar.

A reader with high A1C results sent us a question. "I need to lower my A1C -- can diet and exercise be effective?" they asked. "How much of a reversal can you see?" The answer is, yes, A1C can be lowered by lifestyle modifications. This is achieved by minimizing added sugar in the diet, avoiding refined carbohydrates and highly processed foods, getting regular exercise and reaching a healthy weight. Each of these contribute to improving the body's response to insulin. How much you can lower your A1C with lifestyle changes depends on each person's general health, metabolism and genetics. If your doctor has outlined a treatment plan that includes medication, it's important to follow through.

Thank you, as always, for taking the time to write. It's wonderful to hear when a column has helped you, or that you simply find the information useful or instructive. We read every letter, and we will continue to try to respond to as many as possible.

(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 about the new COVID-19 variant called Eris. Will there be a new booster for it? Also, I read that you'll get better immune response if you get all of your COVID shots in the same arm each time. Is this true?

Dear Reader: From the earliest days of the pandemic, health authorities have kept a watchful eye on the emergence of variants of the coronavirus that causes COVID-19. More specifically, they have tracked what are known as variants of interest. These are mutated forms of the original coronavirus that, due to small changes to the genetic code, become more successful at breaking into and infecting host cells.

Among the newest of these is a variant called EG.5, which has come to be known as Eris. It is now the dominant variant in many parts of the world, including the United States. The Centers for Disease Control and Prevention reports that, as of Aug. 21, Eris made up close to 21% of all new COVID-19 infections in the U.S. That's a marked increase over the previous month. However, in terms of symptoms and severity of disease, Eris does not appear to be significantly different from previous variants.

Eris, along with a handful of other variants that are under close scrutiny at this time, is a descendant of the XBB strain of the coronavirus. That strain is the target of the newest generation of coronavirus booster shots. The new coronavirus booster, which still needs regulatory approval from the FDA, is expected to become available sometime this fall. To simplify what has often been a confusing process, the U.S. is shifting to an annual model for COVID-19 boosters for all age groups.

As for your question about which arm to choose for your coronavirus vaccine, new research suggests the decision may play a role in immune response. A recent study found that immune response may indeed be stronger when the COVID-19 vaccine goes into the same arm each time.

Researchers arrived at this conclusion by analyzing data from 303 individuals receiving the original two-dose coronavirus vaccine series. Those who got both shots in the same arm had levels of T cells that were 75% higher than those who switched arms for the second shot. T cells, which are a type of white blood cell, play a crucial role in immune response. Sometimes known as “killer T cells,” they roam throughout the body and attack suspected pathogens.

The researchers suspect the link between vaccine location and higher T cell numbers is due to the proximity of the armpit. T cells are present in lymph nodes, including those located in the armpits. When the immune cells in those lymph nodes are repeatedly stimulated by the vaccine, this could lead to a more robust immunological response. Proving whether this is actually the case will require a larger and longer study. But in the meantime, there is no harm in picking one arm in which to receive all of your COVID vaccines.

(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 was surprised to read that there have been several cases of locally acquired malaria diagnosed near my home in Florida. I didn't realize that we still have malaria in the United States. Is it widespread? I would appreciate information about symptoms to look out for.

Dear Reader: Malaria is a serious -- and potentially deadly -- mosquito-borne illness. The malaria pathogen is a single-celled blood parasite that belongs to the genus Plasmodium. It enters the body via the bite of a female Anopheles mosquito. Only female mosquitos, who need a blood meal in order to produce eggs, bite their prey. Male mosquitos don't bite and don't transmit disease.

Of the 100-plus species of Plasmodium, five are known to infect humans and cause malaria. Once in the blood, they reproduce rapidly, shedding waste and other byproducts. These toxic substances damage and destroy red blood cells, which leads to the symptoms of malaria.

Malaria typically causes flulike symptoms, including fever, chills, shivering, headache, muscle and body aches and exhaustion. Some people experience gastrointestinal symptoms, including nausea, vomiting and diarrhea. Destruction of red blood cells often leads to anemia. And because the parasite takes up residence in the liver, jaundice, which is yellowing of the skin and the whites of the eyes, is common.

How serious someone's case of malaria can become depends on the specific species of Plasmodium causing the infection.

When a patient's symptoms, along with their travel history, suggest a diagnosis of malaria, a blood sample will be obtained for laboratory testing. If Plasmodium is detected, treatment with drugs to kill the parasite, known as antimalarials, will begin. The specific drug that is used depends on the species of parasite that has been identified. Some strains of Plasmodium have become resistant to antibiotics, which necessitates the use of combinations of drugs to manage the infection.

If left untreated, infection can become severe. Malaria can lead to cognitive lapses, kidney failure, severe anemia, seizure, coma and death.

Malaria was widespread in the U.S. for centuries. Thanks to nationally coordinated mosquito abatement policies, along with the advent of window screens, the disease was deemed eradicated in the 1950s. The 2,000 cases now diagnosed in the U.S. each year are largely acquired during travel.

However, as you point out, a handful of cases acquired in the U.S. have recently been diagnosed. Seven of those were located in Florida, and one was in Texas. All of the patients have been successfully treated for the disease. These are the first known cases of local transmission since 2003, when nine cases were identified in the Palm Beach area of Florida.

This newest cluster of malaria cases has caused the Centers for Disease Control and Prevention to notify health care providers and public health authorities via a national health advisory. Meanwhile, travelers to regions where malaria is endemic are urged to take all possible precautions. This includes wearing protective clothing, using insect repellent, sleeping under mosquito netting and taking a protective regimen of antimalarial drugs.

(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.)