Hello, dear readers, and welcome to the bonus letters column that we promised several weeks ago. With a bonanza of mail, these extra letters columns help us keep up with your comments and follow-up questions. We’ve received a lot of virus and vaccine questions, so let’s dive in.

-- The recommendations regarding booster shots continue to evolve, which has led to a bit of confusion. This includes a reader who received the Johnson & Johnson vaccine and a J&J booster. “I understand that you can get an mRNA booster after the J&J shot,” he wrote. “But I haven’t seen anything as to when you can safely get an mRNA booster after receiving two J&J shots. Any guidance would be appreciated.” It is suggested that individuals who received the J&J shot-plus-booster series follow up with either the Pfizer or Moderna boosters four months after their last shot. Since this is a suggestion and not a formal recommendation at this point in time, it’s a good idea to discuss a second booster dose with your health care provider.

-- Another aspect of the COVID-19 landscape that has continued to shift is FDA approval of the vaccines. In a recent column, we mentioned that the Pfizer vaccine has received Food and Drug Administration approval. This led a reader to say he has read otherwise. “Although the vaccine was fully approved, research I have done indicates that version is not in use in the United States, but only in other parts of the world,” he wrote. “Is this correct?” The answer is no, this is not correct. There is only one version of the vaccine, and it is in use throughout the world. We suspect the confusion arises because the vaccine is offered under different brand names outside of the U.S. Despite that, all brand names of Pfizer’s COVID-19 vaccine are biologically and chemically the same.

-- We get a lot of mail regarding antibodies, which are produced as part of the body’s immune response to infection and following vaccination. A reader from Oklahoma had a question on the topic. “I had COVID-19 in December 2020, prior to the availability of vaccines. I later got the Moderna vaccine (both shots), and I got my booster shot in October,” she wrote. “I donated blood three or four times, and each time, my test result for antibodies was negative. Should I be concerned?” No, there is no need for concern. In terms of COVID-19 infection, data shows that up to 40% of people test negative for antibodies. And when it comes to the COVID-19 vaccines and boosters, a negative antibody test does not mean you are unprotected. The protective mechanisms of the vaccines are complex, and efficacy does not rely solely on antibody detection.

Thank you to everyone who has taken the time to write to us. We read each of your letters and respond to as many as we can. A quick reminder that we cannot provide a diagnosis, offer a second opinion or comment on medications. Please stay safe, and continue to take precautions against COVID-19.

(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 rheumatic fever when I was 5 years old. My heart is fine, but after my illness, I had trouble learning. I’m 79 now and still struggle to understand some things, especially the age we live in, with electronic everything. What does rheumatic fever do to the body? Can it affect the brain?

Dear Reader: Rheumatic fever is a complex disease that can develop when a strep infection goes untreated. This infection typically is strep throat, and sometimes it is scarlet fever. Both are caused by infection with group A streptococcal bacteria.

Rheumatic fever occurs mainly in children from 5 to 15 years old, and it usually causes symptoms one to five weeks after infection. When faced with an ongoing strep infection, the child’s immune system can go into overdrive. But instead of targeting just the bacteria, it attacks the body’s own tissues, as well. For this reason, rheumatic fever is regarded as an autoimmune disease. Although the reasons why this occurs are not fully understood, researchers believe that certain molecular features of group A streptococcal bacteria trick the body into attacking its own tissues. This is a mechanism known as molecular mimicry.

Because rheumatic fever affects the heart, blood vessels, joints, skin and brain, it has a wide range of symptoms. These include fever; pain, swelling, heat and tenderness in the joints of the elbows, wrists, ankles and knees; a distinctive rash; shortness of breath; chest pain; a racing heartbeat; weakness; and persistent fatigue.

You asked in your letter about the effect of rheumatic fever on your brain, but also said that your family doctor’s primary worry was about the health of your heart. His concern is well-founded. Although the word “rheumatic” refers to inflammation of the joints, connective tissues and muscles, the disease often adversely affects the heart. Widespread inflammation can do damage to the heart muscle and the heart’s valves.

While heart issues are seen as a primary risk of rheumatic fever, the disease also can affect the brain. Neurological symptoms include a disorder known as Sydenham chorea, which can appear up to six months after the infection has cleared. It’s estimated to occur in up to one-fourth of cases of rheumatic fever, and affects girls more often than boys. Symptoms can be both physical and cognitive, and can range from mild to severe. They include muscular weakness; jerky, uncoordinated movement; facial tics; slurred speech; and a stumbling gait. Some patients have trouble with reading and writing, and they may experience anxiety or emotional instability.

Although most children recover completely, in rare cases the condition can persist or recur. There is some evidence of a link between recurrent cases of Sydenham chorea and the later development of obsessive-compulsive disorder, autism and attention deficit/hyperactivity disorder. Up to 80% of those with Sydenham chorea also develop myocarditis, which is inflammation of the heart.

So much time has elapsed since your original illness, it would be difficult to say if Sydenham chorea has played a role in your life. One thing we can assure you of, however, is that when it comes to the complexities of the digital world, you are not alone in feeling a bit overwhelmed.

(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: The news here in Atlanta is talking about a new tick disease called the heartland virus. Our family spends a lot of time outdoors, so it’s something we’re worried about. What can you tell us about it? It seems like ticks are a bigger problem every year.

Dear Reader: Due to the mild climate in your part of the country, ticks are a year-round concern. And with spring weather warming much of the rest of the nation, regions that get a winter respite from the tiny parasites are seeing their return.

There are more than 80 species of ticks in the United States. Only a handful -- biologists estimate from 10 to 12 species -- commonly bite humans. That still poses a danger because, as most of us know, tick bites can transmit parasites, bacteria and viruses.

In recent years, the geographic range of various tick species has been expanding. This has led to a jump in the number of tick-borne infections reported each year. At the same time, biologists continue to identify new pathogens carried by ticks that cause disease in humans. Among these is the heartland virus that you’re asking about.

Different species of ticks carry different diseases. For the heartland virus, it’s the Lone Star tick. It’s a reddish-brown tick with a rounded body. Adults are about one-quarter of an inch long. Females have a white splotch on their backs, the so-called “Lone Star.” In males, white markings at the edges of the body resemble a horseshoe. It inhabits the southeastern, south-central and eastern states and is the most common tick in Georgia.

We have previously written about how a bite from a Lone Star tick can lead to alpha-gal syndrome, in which the person who was bitten becomes allergic to red meat. Now, researchers at Emory University in Atlanta have found that the Lone Star tick has become a potential carrier of the heartland virus. It’s a rare disease, with about 50 cases identified since its discovery in Missouri in 2009. However, as is common with diseases that health care providers aren’t familiar with yet, the actual number of cases is probably higher.

Symptoms are in line with other tick-borne diseases, including fever, headache, nausea, diarrhea, fatigue and muscle or joint pain. Diagnosis is via a patient's physical symptoms, their history of tick exposure and appropriate laboratory tests. There are no vaccines or medications to prevent or treat infection with heartland virus. Instead, patients receive supportive care that addresses their symptoms.

The best defense is to protect yourself. A tick perches on a bit of vegetation, legs outstretched, and waits for a host to brush up against it. So cover up when outdoors, preferably in light-colored clothes, which make ticks more visible. Be vigilant about checking your clothes, hair and skin for ticks when you return from an outing. And be sure to check your pets.

If bitten, use tweezers to grasp the tick as close to the skin as possible. Remove with a steady, even pressure, then clean the area with soap and water. If symptoms develop, it’s vital to seek medical care.

(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.)