Dear Doctor: First, there was a "superbug bacteria"; now there's a "superbug fungus"? What is this new fungus that I've been reading about? More to the point, how worried should I be?

Dear Reader: Unfortunately, yes, a type of yeast known as Candida auris has been identified as a source of serious illness in a growing number of hospital patients, both in the United States and abroad. Not only is it resistant to existing treatments, it has also eluded efforts by health care personnel to halt its spread.

Yeasts are single-celled microorganisms that are members of the fungus kingdom, which also includes molds and mushrooms. They're everywhere -- in the soil, on vegetation, in waterways and on living creatures, including humans.

Candida yeasts are typically found in the intestinal tract, as well as on mucous membranes and other areas of warm, moist skin. While more than 150 species of Candida have been identified, only about 15 of them are known to cause infections.

For the most part, these tiny organisms live peaceably with their hosts, held in check by the other microbiota that call us humans home. However, factors like stress, taking antibiotics or antifungals, and a weak immune system, to name just a few, can lead to an overgrowth of Candida yeasts. This can result in symptoms such as itching, rash, fatigue or gastrointestinal distress, which vary depending on the area that is infected.

The good news is that most Candida infections are easy to recognize and respond well to treatment. If you've ever had athlete's foot, a vaginal yeast infection, jock itch, diaper rash or oral thrush, then you've had a Candida fungus skin infection. Nail fungus, also caused by Candida, is more difficult to eradicate due to its positioning beneath the nail bed.

The very bad news is that unlike its relatives, Candida auris is emerging as a serious health threat. First identified in 2009 in Japan, the organism has spread globally. As of August 2017, it was responsible for 112 infections in the U.S., more than half of those in 15 different New York City hospitals.

Candida auris is resistant to all three major classes of antifungal drugs. It persists in hospitals and is spread between patients. It's particularly dangerous to people with weak immune systems, such as newborns and the elderly. It can enter a patient's blood stream via wounds, as well as lines or tubes entering the body. Once in the body, it can cause serious invasive infections. Rapid response is crucial, but it is made difficult because Candida auris is difficult to identify.

At first, travel was suspected in the global spread of Candida auris. However, genome sequencing, which is basically a DNA fingerprint, revealed enough differences between regional strains to suggest the yeast has sprung up independently. Needless to say, all aspects of Candida auris are now under intense study.

For all these dire details, you don't have to be alarmed. In most cases, infections occurred in patients who were hospitalized, most of them for several weeks. In the meantime, identifying new treatments and stopping the spread of Candida auris has become an international priority.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Can marijuana use really increase the risk of high blood pressure, as a recent study suggests? I thought marijuana was supposed to make you relax.

Dear Reader: If you'll recall, there was a time when smoking tobacco was similarly touted as a healthy way to relax. Only after years of study and national educational campaigns did the public began to realize the detriments of tobacco. Today, in the desire to legalize marijuana, proponents have focused on its potential health benefits. That doesn't mean it has no negative effects.

In fact, smoking marijuana leads to an increase in heart rate, increased contraction of the heart and a small increase in blood pressure. The 2017 European Journal of Preventive Cardiology study you mentioned attempted to quantify these negative effects.

The data used in the study come from a national survey in 2005 in which people over the age of 20 were asked: "Have you ever used marijuana or hashish?" Participants who answered "yes" were termed "marijuana users." The authors also asked the year that people first used marijuana, from which they calculated total years of use. The authors then looked at mortality data from 1991 to 2011.

In this study, 56.5 percent of the 1,213 eligible participants were qualified as marijuana users. Note that 63 percent of these "users" also had a history of smoking tobacco. The overall death rate of marijuana users was 29.7 percent, while in non-users the rate was 26.2 percent. The authors found that the death rate from high blood pressure was 4.3 percent higher in the users of marijuana, but they didn't find a difference in death rates from heart attacks or strokes.

But let's look at the major problems with this study. First, the definition of "marijuana user" was problematic. People who used marijuana once in their lifetime were quantified as marijuana users. The data didn't differentiate between someone who had used marijuana every day for the last 20 years and someone who used it once in college. Next, the number of participants was relatively small, which affects the conclusiveness of the findings. For example, in this study, cigarette smokers had less risk of dying from a heart attack than did non-smokers. That runs counter to large trials showing the opposite. Lastly, many of the marijuana smokers also smoked cigarettes -- so if the data about cigarette smokers were inaccurate, as the suspect finding suggests, there may be further inaccuracies in the data.

However, the study does highlight that marijuana users had a higher rate of high blood pressure. This was also found in a 2016 study showing a mild elevation of blood pressure in marijuana users. Among people who used marijuana one to six days per month, the systolic blood pressure was elevated by 1.3 points on average, and among those who used 21 to 30 days per month, the systolic blood pressure was elevated by 2.6 points on average.

All these data point to how poorly we understand the health consequences of marijuana use. For example, we simply don't know whether marijuana smoking has the same negative vascular effects as tobacco smoking. With less fear of incarceration over marijuana use, perhaps more people will participate in larger studies to assess marijuana's effect upon the cardiovascular system.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: My husband was in the hospital recently, and at night he would get quite agitated. He yelled, took off his clothes and tried to pull out his IV. He had to be secured to his bed to keep him from leaving. But in the morning, he'd be fine and couldn't remember anything from the night before. What's happening? How can I help?

Dear Reader: What you've described is a few of a group of behaviors commonly known as sundowning, or sundowner, syndrome. It's a descriptive term, not a psychiatric diagnosis. However, it's broadly recognized as anxiety, confusion or agitation that is triggered by the onset of waning daylight. Sundowning can begin anywhere from late afternoon to late evening, and usually resolves in the morning, with the return of daylight.

In addition to the symptoms that you mentioned, people may have mood swings, become demanding, suspicious or even paranoid, hallucinate, hear voices, pace or become unaware of time and place. While sundowning is most commonly observed in people with dementia, impaired cognition and Alzheimer's disease, it can also affect individuals who are institutionalized.

Exactly what causes these behaviors to develop isn't yet known. However, in addition to the low light and emerging shadows that give the syndrome its name, triggers can include fatigue, sleeplessness, lack of mental stimulation, disrupted circadian rhythms and the presence of an infection, such as a urinary tract infection.

To see your loved one vanish into the throes of sundowning is upsetting and painful. But once an episode has begun, neither logic nor coaxing can help. Don't try to talk or reason the person out of their fears. If they are hallucinating, don't try to bring them into the present. The best thing you can do is stay calm and be reassuring.

Over the long term, approaches to managing this behavior include:

-- Set up a daily routine with consistent waking and bed times, and regular mealtimes. This will form a predictable framework that can help the individual feel safe.

-- Schedule any taxing activities for early in the day, when the person is at their best. Try not to do more than one or two significant activities, like a doctor's appointment, a shopping trip, or visits from friends or relatives, per day.

-- Watch the diet for any possible triggers. If it turns out that caffeine and sugar cause problems, consider eliminating them, or limit them to earlier in the day.

-- As daylight fades, turn on lots of lights and close the curtains. Limiting noise can also be helpful.

-- Check with your family doctor to see whether a supplement like melatonin may help with sleep cycles.

We are keenly aware of the mental and emotional challenges of being the caregiver at a time like this. That's why we think it's so important that you take time -- make the time -- to care for yourself as well. Take regular breaks, enlist outside help and see a counselor to help process what you're going through. It will bolster your own health and will help you to be an even more effective caregiver.

And if any of you readers have successful strategies we haven't mentioned that you'd like to share, we'd love to hear from you.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)