The Myopia Pandemic

August 28, 2015 by

Aug. 28, 2015

By Medical Discovery News

The Myopia Pandemic

You’ve probably heard of pandemics – the plague, influenza, HIV – but you might not have seen coverage of the growing myopia pandemic. Before you consider bathing in sanitizer, you should know that myopia isn’t contagious. Another word for it is nearsightedness.

Myopia is a condition in which close objects are seen clearly but distant objects are blurred due to the elongation of the eye or too much curvature of the cornea. This causes light entering the eye focusing in front of the retina rather than on it. Myopia is different than hyperopia, which is the kind of nearsightedness that comes from growing older. In fact, the myopia pandemic is primarily affecting young people.

It currently affects 90 percent of the young adults in China, although 60 years ago it was 10-20 percent. In the United States and Europe it affects about half of all young adults, double what it was 50 years ago. Seoul has the highest incidence: 96.5 percent of young people in South Korea’s capital have myopia. An estimated 2.5 billion people will experience myopia by 2020.

Vision issues can be corrected with glasses, contact lenses, or surgery, but none of those fix the underlying defect. Eye elongation can stretch and thin parts of the inner eye, which can increase the risk of retinal detachment, glaucoma, cataracts, and even blindness.

Genetic causes have been discounted, so this rapid change has to come from something in the environment. More than 400 years ago, Johannes Kepler, an astronomer and expert in optics, wrote that his intense studying led to nearsightedness. Today, students are not only studying a great deal but are also spending much of their time with cell phones, tablets, computers, and video games, primarily indoors.

Intense periods of reading and studying were disproved as a cause of myopia during a study in 2000. Seven years later, scientists from Ohio State University followed more than 500 eight- and nine-year-olds with healthy vision and tracked the time they spent outdoors. After five years, 20 percent had developed myopia, which correlated to the time they spent indoors. This was confirmed one year later, when scientists in Australia studied 4,000 students and also reported that the amount of time spent indoors was the important factor.

It’s probably because the retina of the eye produces and releases more dopamine, a neurotransmitter, during the day to signal the eye to switch from night to daytime vision. Indoor light disrupts this cycle, affecting eye development. Only 30 percent of Australian children who spent three or more hours outside each day had myopia. A systematic review paper aggregated previous studies and concluded that each hour of each week spent outside reduces a child’s chance of developing myopia by 2 percent.

Researchers are examining possible ways to control the development of myopia, such as altering the way contact lenses focus light, producing eye drops that block neurotransmitter release, and using artificial lights like those used to treat seasonal affective disorder, also known as winter depression. Of course, having children play or simply be outside seems the best option, and it has other health benefits too.

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The Plague: It was the Gerbils

August 28, 2015 by

Aug. 7, 2015

By Medical Discovery News

In the past 800 years, many things have been blamed for the plague that swept through Europe in the Middle Ages: the alignment of the planets, bad air, lack of proper hygiene, black rats, and their fleas. Now scientists have data that suggests the climate in Central Asia at that time influenced the size of the great gerbil population, which triggered cycles of plague in Europe. These furry little rodents carried the plague bacterium, as did the fleas that fed on them. When the gerbil population shrank, the fleas found alternate hosts like horses, humans, and eventually rats, which then made their way to Europe and triggered the plague pandemics.

The plague was caused by the bacterium Yersinia pestis. It is transmitted to humans through the bite of a flea that has fed on an infected rodent. Plague outbreaks have afflicted humans for thousands of years and changed the course of history. The first recorded plague pandemic began in 541 and was named the Justinian Plague after the 6th century Byzantine emperor. Frequent outbreaks for the next 200 years are likely to have killed over 25 million people. The second pandemic, called the Great Plague or the Black Death, began in China and spread westward along trade routes to Constantinople and into Europe. About 60 percent of Europeans died, eliminating entire towns.

The third pandemic, or Modern Plague, also began in China and spread to Hong Kong by 1894. Rats hitching rides on steamships spread the plague to port cities around the world for the next 20 years, killing about 10 million people. By then scientists were able to identify the bacterium responsible and how it spread. Efforts to control the rat population eventually ended the pandemic. It continued to infect people (although in much smaller numbers than before) during the 20th century, such as in Vietnam during the war. The bacterium is still in the reservoir of wild rodents, and today most cases of plague are in sub-Saharan Africa and Madagascar. The plague can be effectively treated with common antibiotics, but if left untreated it has a high mortality rate.

Since there are still lots of rats in Europe, some wonder, why is there no plague? Researchers proposed that each time, the plague actually started in Asia. To test their theory, they examined climate records using the rings of trees. The incidence of plague did not correlate with climate changes in Europe, but it did with changes in Asia. It was already known that the Asian great gerbil carries Yersinia pestis, and when the weather in Asia was good, gerbils thrived, but when it turned bad, their population would crash. Then their fleas would seek another host such as human traders and their pack animals, who spread the plague to other parts of the world. They found no evidence that rodents in Europe carried Yersinia pestis, so that would explain why cases of the plague disappeared between pandemics.

So don’t worry about the little gerbils in the pet store – they are not carrying the plague.

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When An Epidemic Becomes a Pandemic

August 2, 2012 by

By Medical Discovery News

July 7, 2012

For at least thousands of years, people have suffered flu epidemics and pandemics.  In 412 B.C., Hippocrates described what was likely an influenza epidemic in Ancient Greece. The term influenza comes from 15th century Italy, when people believed stars influenced the illness because it always came in cycles. Soon after, in 1580, the first clear account of a flu pandemic was written. From that point on, records show flu pandemics have been recurring every one to three decades somewhere in the world.

So what is the difference between an epidemic and pandemic? Flu epidemics occur every year because each year the virus comes back just slightly different. In a flu pandemic, a much larger geographic area is affected, sometimes worldwide, when a new strain of the virus infects people for the first time and everyone is susceptible.

The World Health Organization has defined three phases of pandemics. The first, or earliest, is called the Inter-Pandemic period. During this time, no new influenza viruses are detected in humans, but new flu viruses could be circulating in animal populations.

The next level is the Pandemic Alert period. Here, the flu virus is infecting humans but is either incapable or has limited ability for human-to-human transmission. The last is the Pandemic period where there’s widespread and rapid transmission in human populations.

The potential for a flu virus to be capable of causing pandemics lays in its ability to infect many different species including horses, pigs, and birds. As various strains of the flu virus spread from species to species, multiple viruses can infect the same animal, allowing the viruses to exchange genetic information and create a new virus. Once it can infect and efficiently transmit between humans, a pandemic starts.

The annual flu epidemic sickens 20 percent of America’s population and kills 40,000 people, creating a $10 billion loss in productivity and medical costs. Imagine the cost of a pandemic.  The largest recorded was the 1918 Spanish flu pandemic, which killed 675,000 people in America and 20 to 40 million people worldwide.

Today, health officials worry about avian flu (H5N1) and whether, or more likely when, this flu strain will start a new pandemic. The H5N1 virus was first recognized in Hong Kong in 1997.  Since then it has spread extensively throughout Asia and can now be found in the Middle East, Africa, and Europe. The virus is in the Pandemic Alert period with no means yet for extensive human-to-human transmission. As of spring 2012, approximately 600 people have been diagnosed with H5N1 and the mortality rate is an alarming 60 percent.

In order to understand how this virus may attain efficient transmission between people, American and Dutch scientists created a transmissible H5N1 in the lab. The controversial study could help other scientists create a vaccine for when an avian flu pandemic occurs. But others fear this research could provide a “blueprint” for terrorists to create a potential biological weapon.

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