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| SOURCE: GEO.TV |
Daniswicz, a sophomore at Northwestern University who lost her lower leg to bone cancer, is training the computer to recognize slight movements in her thigh so she can eventually be fitted with a "bionic" leg -- a robotic prosthesis she would control with her own nerves and muscles.
"We're really integrating the machine with the person," said Levi Hargrove, a research scientist at the Rehabilitation Institute of Chicago's Center for Bionic Medicine who is leading the project.
Daniswicz is part of a clinical trial sponsored by the U.S. Army that is using electromyography -- electrical signals produced by muscles -- and pattern recognition computer software to control a new generation of robotic limbs.
Electrodes attached to nine different muscles in the thigh act as antennas, picking up electrical signals sent from the nerves to the muscles. These signals are fired in a specific pattern depending on how a person intends to move.
With a bit of training, the computer can learn a person's signal pattern for when they want to bend a knee or flex an ankle and it makes the virtual reality avatar move.
"The way most prosthetics work now is you have mechanical sensors. You have to push and interact with them," Hargrove said. "With this, you measure the actual neural intent and have that tell the motor what to do."
Researchers at the institute have already developed prosthetic arms directed by nerve impulses. But a robotic leg would give lower limb amputees a new kind of freedom, allowing them to climb stairs more safely and with more natural motion.
Daniswicz has been training her computer avatar since January and she can now instruct it to bend and straighten its knee, and flex and straighten its ankle, just by making slight movements in her thigh muscles.
"Hailey has taught the computer what to do, and now, whenever she does it, it listens, interprets and makes the leg on the virtual reality avatar move," Hargrove said.
Daniswicz is one of four volunteers in the study trial that set out to determine whether patients would need surgery to implant additional nerve endings -- a technique called targeted muscle reinnervation -- to control the motorized leg.
SURPRISING FINDING
The team had expected patients to be able to operate the knee joint, but were surprised they could control the ankle without needing surgery, Hargrove and colleagues reported this week in the Journal of the American Medical Association.
Since the trial ended, three more volunteers have had similar results.
"The fact that these findings suggest that you might not need surgery makes the population very broad," Hargrove said.
Currently, there are roughly 2 million lower leg amputees in the world, but that figure is expected to double by 2050 as the number of people with diabetes increases, said Michael Goldfarb, a mechanical engineer at Vanderbilt University in Nashville.
Goldfarb's team is developing a fully robotic lower leg for the project that can be controlled by nerve impulses.
He said most lower limb prosthetics are fairly passive.
"They are better than peg legs," Goldfarb said, "but the amputee has to swing it to get the leg to move."
He said advances in robotic technology are making powered legs possible. "It's a much closer approximation to what our own limb does."
Although a few companies are developing powered knees and ankles, no company makes a lower leg prosthetic with both. And none are controlled by the amputee's nerve signals, he said.
For Daniswicz, the next step is a powered leg.
"We'll make a socket for Hailey. We'll put the electrodes in the same location and have Hailey repeat this motion to control a knee and an ankle," Hargrove said.
"After that, we'll start working on transitions from chairs, and then we'll move to walking," he said.
By the end of the year, Hargrove expects to have patients walking in the lab, and then they can try more challenging activities such as stair climbing and descent.
Hargrove said it is too early to say how long it would be before a "bionic leg" would be available.
"It's through research like this that is making it real."
Here are some exercises that will help you stay fit during your pregnancy.
Remember: Before you start any exercise program, consult with your health care provider. Your health care provider can give you personal exercise guidelines, based on your medical history.
Stretching Exercises for Pregnancy
Stretching exercise make the muscles limber and warm which can be especially helpful when you're pregnant. Here are some simple stretches you can perform before or after exercise.
* Neck rotation: Relax your neck and shoulders. Drop your head forward. Slowly rotate your head to your right shoulder, back to the middle, and over the left shoulder. Complete four, slow rotations in each direction.
* Shoulder rotation: Bring your shoulders forward and then rotate them up toward your ears and then back down. Do four rotations in each direction.
* Swim: Place your arms at your sides. Bring your right arm up and extend your body forward and twist to the side, as if swimming the crawl stroke. Follow with left arm. Do the sequence ten times.
* Thigh shift: Stand with one foot about two feet in front of the other, toes pointed in the same direction. Lean forward, supporting your weight on the forward thigh. Change sides and repeat. Do four on each side.
* Leg shake: Sit with your legs and feet extended. Move the legs up and down in a gentle shaking motion.
* Ankle rotation: Sit with your legs extended and keep your toes relaxed. Rotate your feet, making large circles. Use your whole foot and ankle. Rotate four times on the right and four times on the left.
Kegel Exercises During Pregnancy
Kegel exercises help strengthen the muscles that support the bladder, uterus, and bowels. By strengthening these muscles during your pregnancy, you can develop the ability to relax and control the muscles in preparation for labor and birth. Kegel exercises are also highly recommended during the postpartum period to promote the healing of perineal tissues, increase the strength of the pelvic floor muscles and help these muscles return to a healthy state, and also increase urinary control.
To do Kegels, imagine you are trying to stop the flow of urine or trying not to pass gas. When you do this, you are contracting the muscles of the pelvic floor and are practicing Kegel exercises. While doing Kegel exercises, try not to move your leg, buttock, or abdominal muscles. In fact, no one should be able to tell that you are doing Kegel exercises. So you can do them anywhere!
We recommend doing five sets of Kegel exercises a day. Each time you contract the muscles of the pelvic floor, hold for a slow count of five and then relax. Repeat this ten times for one set of Kegels.
Tailor Exercises for Pregnancy
Tailor exercises strengthen the pelvic, hip, and thigh muscles and can help relieve low back pain.
* Tailor sit: Sit on the floor with your knees bent and ankles crossed. Lean slightly forward, and keep your back straight but relaxed. Use this position whenever possible throughout the day.
* Tailor press: Sit on the floor with your knees bent and the bottoms of your feet together. Grasp your ankles and pull your feet gently toward your body. Place your hands under your knees. Inhale. While pressing your knees down against your hands, press your hands up against your knees (counter-pressure). Hold for a count of five.
Smokers who successfully quit may enjoy yet another health benefit: improved cholesterol profiles. A boost in "good" cholesterol comes with quitting despite weight gain after putting out the last cigarette, hints a new study.If confirmed in future research, the finding could shed light on the strong, yet somewhat mysterious relationship between smoking and heart health. Up to 20 percent of heart disease deaths are currently blamed on smoking, but researchers haven't yet had a clear understanding of what lies behind the effect. Smoking likely affects the cardiovascular system in a variety of ways, including lowered oxygen levels and wear and tear on the heart itself.
Some small studies have also shown that smoking lowers good cholesterol (HDL) and raises bad cholesterol (LDL), lead researcher Dr. Adam Gepner of the University of Wisconsin School of Medicine and Public Health, in Madison, said.
To test the impact of smoking on cholesterol levels more rigorously, and in a realistic setting, Gepner and his colleagues recruited more than 1,500 smokers representative of the current U.S. population, including its high proportion of overweight and obese individuals.
The average participant smoked about 21 cigarettes per day prior to the start of the study. After a year on one of five smoking cessation programs, 334 (36 percent) had succeeded in quitting.
The researchers found that those who stopped smoking experienced an average rise of about 5 percent, or 2.4 milligrams per deciliter (mg/dL), in HDL cholesterol.
Abstainers also experienced an increase in large HDL particles, which are important for lowering heart disease risk as well, report the researchers in the American Heart Journal.
The effects were somewhat stronger in women. However, it did not appear to matter how many cigarettes were smoked at the start of the study: heavy smokers enjoyed the same HDL benefit as lighter smokers after they quit.
One downside of kicking the habit can be weight gain. Sure enough, the group that quit gained an average of about 10 pounds compared to one or two pounds in the group that relapsed to smoking. Many participants were already overweight at the start of the study, with an average body mass index (BMI) of 29.6. (A BMI between 20 and 25 is generally considered healthy).
Adding pounds is known to hurt cholesterol levels, both raising the bad kind and lowering the good kind. As a result, the researchers think the weight gain might have offset some of the beneficial effects seen in the abstainers.
"Further benefits on cholesterol levels may have been actually masked by the weight gain seen after quitting," explained Gepner.
"It is important to counsel quitters about weight gain and the need for a healthy diet and regular exercise during the quitting period," he added.
The researchers caution that their results don't prove that smoking cessation causes improvements in cholesterol. Further research is needed to rule out other possible explanations, including the role of changes in alcohol consumption, which is known to affect HDL.
Gepner also noted that it remains unclear exactly how smoking cessation might affect cholesterol levels, although it could have to do with changes in the proteins that control the breakdown of cholesterol. Smoking can damage these proteins.
Regardless, benefits were seen that might translate into better heart health.
Previous studies have shown, for example, that for every 1 mg/dL increase in HDL cholesterol, the risk of a cardiovascular event drops by up to three percent over 10 years.
Therefore, if the link holds, the improvements in blood lipids alone would decrease the average former smoker's risk of a heart attack or stroke by up to 6 percent over the 10 years after they quit, said Gepner.
Pregnancy is the carrying of one or more offspring, known as a fetus or embryo, inside the womb of a female. In a pregnancy, there can be multiple gestations, as in the case of twins or triplets. Human pregnancy is the most studied of all mammalian pregnancies. Childbirth usually occurs about 38 weeks after conception; in women who have a menstrual cycle length of four weeks, this is approximately 40 weeks from the last normal menstrual period (LNMP). The World Health Organization defines normal term for delivery as between 37 weeks and 42 weeks.One scientific term for the state of pregnancy is gravid, and a pregnant female is sometimes referred to as a gravida. Neither word is used in common speech. Similarly, the term "parity" (abbreviated as "para") is used for the number of previous successful live births. Medically, a woman who has never been pregnant is referred to as a "nulligravida", a woman who is (or has been only) pregnant for the first time as a "primigravida", and a woman in subsequent pregnancies as a multigravida or "multiparous". Hence, during a second pregnancy a woman would be described as "gravida 2, para 1" and upon live delivery as "gravida 2, para 2". An in-progress pregnancy, as well as abortions, miscarriages, or stillbirths account for parity values being less than the gravida number, whereas a multiple birth will increase the parity value. Women who have never carried a pregnancy achieving more than 20 weeks of gestation age are referred to as "nulliparous".
The term embryo is used to describe the developing offspring during the first 8 weeks following conception, and the term fetus is used from about 2 months of development until birth.
In many societies' medical or legal definitions, human pregnancy is somewhat arbitrarily divided into three trimester periods, as a means to simplify reference to the different stages of prenatal development. The first trimester carries the highest risk of miscarriage (natural death of embryo or fetus). During the second trimester, the development of the fetus can be more easily monitored and diagnosed. The beginning of the third trimester often approximates the point of viability, or the ability of the fetus to survive, with or without medical help, outside of the uterus.
Pregnancy occurs as the result of the female gamete or oocyte merging with the male gamete, spermatozoon, in a process referred to, in medicine, as fertilization, or more commonly known as "conception". After the point of fertilization, it is referred to as a zygote or fertilized egg. The fusion of male and female gametes usually occurs through the act of sexual intercourse, resulting in spontaneous pregnancy. However, the advent of artificial insemination and in vitro fertilisation have also made achieving pregnancy possible in cases where sexual intercourse does not result in fertilization (e.g., through choice or male/female infertility).
The process of fertilization occurs in more than a single step, and the interruption of any of these can lead to a failure. Therefore, what is commonly known as "conception" is much more than the fusion between the female gamete and male spermatozoon. Through fertilization, the egg and sperm are saved: the egg is activated to begin its developmental program, and the haploid nuclei of the two gametes come together to form the genome of a new diploid organism At the very beginning of the process, the sperm undergoes a series of changes which makes pregnancy likely to occur. As freshly ejaculated sperm is unable or poorly able to fertilize,the sperm undergoes the phenomenon called capacitation. It is estimated that during the ejaculation, 300,000,000 sperm are released, from which only 200 reach the oviduct. Capacitation is the process through which the spermatozoon is prepared for the merging with the egg. Capacitation occurs in 5 to 6 hours and it takes place once the sperm reaches the vagina. This is also the process through which the spermatozoon becomes hyperactivated and prepared for the acrosome reaction. In order to be able to fecundate the egg, the sperm must get through the coat surrounding the egg, the so called "zona pellucida". Once the zona pellucida is penetrated, the sperm is able to reach the oocyte. However in order to get through the egg's coat, the sperm undergoes an acrosome reaction that provides it with an enzymatic drill which is able to penetrate the zona pellucida. The acrosome itself is a modified lysosome, situated on the anterior part of the head of the sperm.
Once a sperm penetrates the zona pellucida, it binds to and fuses with the plasma membrane of the oocyte. Binding occurs at the posterior (post-acrosomal) region of the sperm head. After binding occurs, the egg must also undergo a series of metabolic and physical changes which may influence the further development of the zygote. These changes are called in medicine egg activation, mainly because prior to fertilization, the egg is in a latent state.
Methods to assist reproduction also include intracytoplasmic sperm injection, gamete intrafallopian transfer (GIFT), zygote intrafallopian transfer (ZIFT), and embryo cryopreservation (frozen fertilized egg and sperm). These techniques are considered as alternatives to get pregnant by women who have tried unsuccessfully for at least one year. It is estimated that in the United States, more than 6 million adults, or 10% of the adult population, are affected by infertility
The expected date of delivery (EDD) is 40 weeks counting from the first day of the last menstrual period (LMP), and birth usually occurs between 37 and 42 weeks. The actual pregnancy duration is typically 38 weeks after conception. Though pregnancy begins at conception, it is more convenient to date from the first day of a woman's last menstrual period, or from the date of conception if known. Starting from one of these dates, the expected date of delivery can be calculated using the Naegele's rule for estimating date of delivery. A more accurate and sophisticated algorithm takes into account other variables, such as whether this is the first or subsequent child (i.e., pregnant woman is a primip or a multip, respectively), ethnicity, parental age, length of menstrual cycle, and menstrual regularity.
Pregnancy is considered "at term" when gestation attains 37 complete weeks but is less than 42 (between 259 and 294 days since LMP). Events before completion of 37 weeks (259 days) are considered preterm; from week 42 (294 days) events are considered postterm.When a pregnancy exceeds 42 weeks (294 days), the risk of complications for both the woman and the fetus increases significantly. As such, obstetricians usually prefer to induce labour, in an uncomplicated pregnancy, at some stage between 41 and 42 weeks.
Recent medical literature prefers the terminology preterm and postterm to premature and postmature. Preterm and postterm are unambiguously defined as above, whereas premature and postmature have historical meaning and relate more to the infant's size and state of development rather than to the stage of pregnancy.
Fewer than 5% of births occur on the due date; 50% of births are within a week of the due date, and almost 90% within 2 weeks. It is much more useful and accurate, therefore, to consider a range of due dates, rather than one specific day, with some online due date calculators providing this information.
Accurate dating of pregnancy is important, because it is used in calculating the results of various prenatal tests (for example, in the triple test). A decision may be made to induce labour if a fetus is perceived to be overdue. Furthermore, if LMP and ultrasound dating predict different respective due dates, with the latter being later, this might signify slowed fetal growth and therefore require closer review.The age of viability has been receding because of continued medical progress. Whereas it used to be 28 weeks, it has been brought back to as early as 23, or even 22 weeks in some countries.
Skipping breakfast may not change how much food a kid eats during the rest of the day, suggests a new study.But missing the morning meal still carries consequences, the researchers caution.
Some evidence has suggested that the increasingly common practice of skipping breakfast could lead kids to overeat at later meals, and eventually pack on extra pounds. Yet few studies have rigorously tested whether that's what really happens, lead researcher Tanja Kral of the University of Pennsylvania School of Medicine, in Philadelphia, said.
Kral and her colleagues set out to assess the effect of skipping breakfast on appetite and total calories consumed during the rest of the day among 21 kids between the ages of 8 and 10, most of them regular breakfast eaters.
Each child visited the testing lab twice. One time they were fed a breakfast of cereal, milk, banana and orange juice; on the other visit they were not. On both occasions, the kids were later served lunch, which they could choose from an array of foods -- including pasta, broccoli, applesauce and cookies -- and told they could eat as much or as little as they wanted over a period of 20 minutes.
The children were then free to leave the lab and parents reported back what the kids consumed during the remainder of the day.
Not surprisingly, kids said they felt hungrier throughout the morning when they did not eat breakfast.
However, that didn't necessarily translate into larger lunches, report the researchers in The American Journal of Clinical Nutrition.
"We found that despite differences in feelings of hunger and fullness, children who regularly consume breakfast did not make up for the missing calories from a skipped breakfast on a single occasion by eating more later in the day," said Kral.
As a result, the kids who ate breakfast ended up consuming more calories overall, and more than they needed to maintain their current weights.
The average kid took in 362 more calories on days when they did eat breakfast, pushing them about 20 percent over their estimated daily energy requirement -- a number based on height, weight, sex and activity levels.
The disconnect between the kids' stated hunger levels, physical energy needs, and how much they actually ate may be explained by other factors, the authors speculate.
"A child's food intake is very much influenced by factors in the environment, such as the amounts and types of foods that are available," Kral explained. "Hence, these environmental factors can override feelings of hunger and fullness."
Kral noted that studying children with a wider range of body weights and ages, or kids who regularly skip breakfast, might have yielded different results.
She also cautioned that their findings do not support skipping breakfast, which is still important for other reasons.
"Breakfast is an important part of a healthy diet," said Kral. "A healthy breakfast provides many important nutrients that are crucial for children's growth and development."
"Children who skip breakfast may not make up for those missing nutrients later in the day," she added.
Cereal maker General Mills supported the study and supplied the breakfast cereals used in the tests.
Stem cells can be transformed into the pancreatic cells needed to treat diabetes and into complex layers of intestinal tissue, scientists demonstrated in two experiments reported on Sunday.In one, a team turned immature sperm cells into pancreatic tissue, while another team turned embryonic stem cells into complex layers of intestinal tissue.
Both studies show new ways to use stem cells, which are the body's master cells and which can come from a variety of sources.
A team at Georgetown University in Washington worked with spermatogonial stem cells, master cells that give rise to sperm in men.
Ian Gallicano and colleagues used germ-derived pluripotent stem cells, which are made from the spermatogonial stem cells. They nurtured these cells in the lab with compounds designed to make these cells start acting like pancreatic beta cells, which produce insulin.
When transplanted into diabetic mice, these cells produced insulin, acting like the pancreatic beta cells that the body mistakenly destroys in type-1 diabetes, Gallicano's team told a meeting of the American Society for Cell Biology in Philadelphia.
Currently, children and young adults diagnosed with type-1 diabetes must take insulin for life.
A few may be treated with the so-called Edmonton Protocol, in which the missing pancreatic cells are transplanted from cadavers. But there is a shortage of these cells and the patients may suffer from graft-versus-host disease if the cells are not a good match.
Gallicano said men's own cells could be used as a source of their transplants, and he said perhaps the approach may work in women too. "While these cells come from the human testis, the work here is not necessarily male-centric," they wrote. "These fundamental aspects could easily be applied to the female counterpart, oocytes."
Separately, James Wells and colleagues at Cincinnati Children's Hospital Medical Center in Ohio turned two different kinds of stem cell into complex layers of intestinal tissue.
They used both human embryonic stem cells -- taken from days-old embryos -- and induced pluripotent stem cells -- made from ordinary cells transformed by introducing certain genes.
Both types have the power to give rise to all the cell and tissue types in the body when cultured in the lab like the Georgetown team did.
Writing in the journal Nature, Wells's team showed they could transform these cells into what they called organoids -- batches of intestinal tissue made out of the layers of the various cells that make up intestine, including muscle cells and the cells that line the inside of the gut and that produce several vital compounds.
These organoids can be used to study intestinal diseases such as necrotizing enterocolitis, inflammatory bowel diseases and short-gut syndromes and perhaps could be used to treat them someday, Wells's team said.
HEPATITIS A IS SERIOUS LIVER DISEASE CAUSED BY HEPATITIS A VIRUS [HAV].HAV IS FOUND IN TH STOOL OF PERSONS WITH HEPATITIS A. IT IS USUALLY SPREAD BY CLOSE PERSONAL CONTACT AND SOMETIME BY EATING FOOD OR DRINKING WATER CONTAINING HAV. IT IS COMMON IN COUNTRIES SUCH AS PAKISTAN WHERE SANITARY CONDITION ARE SUBSTANDARD.HOW DO I KNOW IF I HAVE HEPATITIS A?
INDIVIDUALS WITH HEPATITIS A EXPIRATION AN ABRUPT ONSET, NAUSEA AND ABDOMINAL DISCOMFORT , FOLLOWED BY JAUNDICE WITHIN A FEW DAYS. THE DISEASE MY RANGE FROM MILD [LASTING 1-2 WEEKS] TO SEVERE DISABLING DISEASE [ LASTING SEVERAL MONTHS]. IN AREAS HIGHLY ENDEMIC FOR HEPATITIS A, MOST INFECTIONS OCCUR DURING CHILDHOOD.
IS HEPATITIS A CONTAGIOUS
HEPATITIS A VIRUS IS TYPICALLY ACQUIRED BY INGESTING FOOD OR WATER THAT HAS BEEN CONTAMINATED WITH THE STOOL OF PERSON WITH HEPATITIS A. THIS TYPE OF TRANSMISSION IS CALLED "FAECOL-ORAL". DIRECT PERSON TO PERSON SPREAD IS COMMON UNDER POOR HYGIENIC CONDITIONS TOP. FOR THIS REASON, THE VIRUS IS MORE EASAILY SPREAD IN AREAS WHERE THERE ARE POOR SANITARY CONDITIONS OR WHERE GOOD PERSONAL HYGIENE IS NOT ABSERVED.
HOW CAN YOU OVOID HEPATITIS A?
- ALWAYS WASH YOUR HANDS AFTER USING THE BATHROOM, OR BEFORE PREPARING OR EATING FOOD
- HOWEVER, HEPATITIS A VACCINE IS THE BEST PROTECTION.
WHO SHOULD GET HEPATITIS A VACCINE AND WHEN ?
SOME PEOPLE SHOULD BE ROUTINELY VACCINATED WITH HEPATITIS A VACCINE:
- ALL CHILDREN 1 YEAR [12 THROUGH 23 MONTHS OF AGE
- PERSON 1 YEAR OF AGE AND OLDER TRAVELING TO OR WORKING IN COUNTRIES WITH HIGHT OR INTERMEDIATE PREVALENCE OF HEPATITIS A, SUCH AS AFRICA, CENTRAL OR SOUTH AMERICA, AND EASTERN EUROPE
HEPATITIS A VACCINE MIGHT BE RECOMMENDED FOR CHILDREN OR ADOLESCENTS IN COMMUNITIES WHERE OUTBREAKS OF HEPATITIS A ARE ACCURING.
TOW DOSES OF THE VACCINE ARE NEEDED FOR LASTING PROTECTION. THESE DOSES BE GIVEN AT LEAST 6 MONTH APART .
HEPITITIS A VACCINE MY BE GIVEN AT THE SAME TIME AS OTHER VACCINES.
IS HEPITITIS A VACCINE SAFE?
YES, HEPATITIS A VACCINE HAS AN EXCELLENT SAFETY PROFILE. NO SEIOUS ADVESE EVENTS HAVE BEEN ATTRIBUTED DEFINITEIVELY TO HEPATTIS A VACCINE. SORENESS AT THE INJECTION SITE IS THE MOST FREQUENTLY REPORTED SIDE EFFECT
WHO SHOULD NOT GET HEPATITIS A VACCINE?
ANYONE:
- WHO HASE EVER HAD A SEVERE [LIFE THREATENING] ALLERGIC TO A PREVIOUS DOSE OF HEPATITIS A VACCINE.
- WHO HAS A SEVER [LIFE THREATENING ALLERGIC REACTION TO ANY VACCINE COMPONENT. ALL HEPATITIS VACCINE CONTAINS ALUM WHILE SOME CONTAIN 2- PHENOXYETHANOL
- WHO IS MODERATELY OR SVERELY ILL AT THE TIME THE SHOT IS SHEDULED TO BE ADMINISTERED
- WHO MIGHT BE PREGNANT , AS THE SAFETY OF HEPATITIS A VACCINE HAS YET NOT BEEN DETERMINED IN PREGNANT WOMEN.HOWEVER THERE IS NO EVIDENCE THAT IT IS HARMFUL TO THE PREGNANT WOMEN OR HER UNBORN BABY
GET YOUR CHILD VACCINATED
FOR MORE INFORMATION ASK YOUR
HEALTHCARE PROVIDER
Hepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus (HAV), which is most commonly transmitted by the fecal-oral route via contaminated food or drinking water. Every year, approximately 10 million people worldwide are infected with the virus. The time between infection and the appearance of the symptoms, (the incubation period), is between two and six weeks and the average incubation period is 28 days.In developing countries, and in regions with poor hygiene standards, the incidence of infection with this virus is high and the illness is usually contracted in early childhood. HAV has also been found in samples taken to study ocean water quality. Hepatitis A infection causes no clinical signs and symptoms in over 90% of infected children and since the infection confers lifelong immunity, the disease is of no special significance to the indigenous population. In Europe, the United States and other industrialized countries, on the other hand, the infection is contracted primarily by susceptible young adults, most of whom are infected with the virus during trips to countries with a high incidence of the disease.
Hepatitis A does not have a chronic stage, is not progressive, and does not cause permanent liver damage. Following infection, the immune system makes antibodies against HAV that confer immunity against future infection. The disease can be prevented by vaccination, and hepatitis A vaccine has been proven effective in controlling outbreaks worldwide.
