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March 08, 2010

Hand sanitizers do nothing against the flu

Can hand sanitizers like Purell really stop people from getting the flu? - By Darshak Sanghavi - Slate Magazine And their efficacy against other diseases is suspect as well.
Yet the data tell a less compelling story about sanitizers like Purell. In 2005, Boston-based doctors published the very first clinical trial of alcohol-based hand sanitizers in homes and enrolled about 300 families with young children in day care. For five months, half the families got free hand sanitizer and a "vigorous hand-hygiene" curriculum. But the spread of respiratory infections in homes didn't budge, a result that "somewhat surprised" the researchers. A Columbia University study also found no reduction in common infections among inner-city families given free antibacterial hand soap, detergent, and cleaning supplies. The same year, University of Michigan epidemiologist Allison Aiello summarized data on hand hygiene for the FDA and pointed out that three out of four studies showed that alcohol-based hand sanitizers didn't prevent respiratory infections. Then, in 2008, the Boston group repeated the study—this time in elementary schools—and threw in free Clorox disinfecting wipes for classrooms. Again, the rate of respiratory infections remained unchanged, though the rate of gastrointestinal infections, which are less common than respiratory infections, did fall slightly. Finally, last October, a report ordered by the Public Health Agency of Canada concluded that there is no good evidence that vigorous hand hygiene practices prevent flu transmission. Why, then, do so many people think widespread use of hand sanitizers like Purell are the cornerstone of flu prevention? To be sure, hand-washing can save lives in medical settings. In 1847, Hungarian doctor Ignaz Semmelweis discovered that washing one's hands with chlorine between deliveries practically eliminated fatal infections among laboring women. (His colleagues ignored him and later committed him to a mental hospital, where he was beaten to death by guards.) Today, numerous modern studies show that in randomized trials, meticulous hand-washing, when coupled with other infection control measures like surgical draping and universal gloving, reduce the rate of life-threatening infections during surgery and intensive care unit stays. But in hospitals, outside of these clinical trials, just half of doctors and nurses regularly clean their hands before patient care, despite widespread publicity. More worrisome: In hospitals where massive educational efforts have increased hand-washing rates from 40 percent up to 70 percent, there has been no overall reduction in infection rates. Even in highly regulated places like hospitals, the promising benefits of hand-washing remain largely unrealized.

March 07, 2010

Scientists in Michigan discover AIDS hides in bone marrow

Researchers: AIDS virus can hide in bone marrow
The virus that causes AIDS can hide in the bone marrow, avoiding drugs and later awakening to cause illness, according to new research that could point the way toward better treatments for the disease. . . . Dr. Kathleen Collins of the University of Michigan and her colleagues report in this week's edition of the journal Nature Medicine that the HIV virus can infect long-lived bone marrow cells that eventually convert into blood cells. The virus is dormant in the bone marrow cells, she said, but when those progenitor cells develop into blood cells, it can be reactivated and cause renewed infection. The virus kills the new blood cells and then moves on to infect other cells, said. "If we're ever going to be able to find a way to get rid of the cells, the first step is to understand" where a latent infection can continue, Collins said.

March 06, 2010

The front of the asteroid hit the Earth while the far side was still out in the upper atmosphere

According to New Comprehensive Review, a Giant Meteorite Caused the Dinosaur Extinction | Popular Science
In the late 1970s, a geophysicist discovered an impact crater in Yucatan, Mexico, and analysis showed the crater's date of origin to be the end of the Cretaceous. Geologic data indicate that the meteorite that produced the Chicxulub crater -- which lies partially buried beneath the Yucatan Peninsula -- was between 10 and 15 kilometers (6 and 10 miles) in diameter and caused an explosion on Earth that was a billion times more powerful than the Hiroshima atomic bomb. The material that blasted into the atmosphere triggered a global winter, and researchers say much of life on Earth was gone within days. Dr. Penny Barton, an author of the review, says "Our work lets us visualise the astonishing events of the few minutes after impact. The front of the asteroid hit the Earth while the far side was still out in the upper atmosphere, punching a hole though the Earth's atmosphere. As the asteroid vapourised explosively, it created a crater 30 km deep and 100 km across, with sides as high as the Himalayas. However within only two minutes the sides collapsed inwards and the deepest parts of the crater rebounded upwards to leave a wide, shallow hollow." "These terrifying events led to darkness and a global winter, resulting in the extinction of more than 70 percent of known species. The tiny shrew-like mammals which were around at that time proved better adapted to survival than the cumbersome dinosaurs, and the removal of these dominant animals paved the way for the radiation of the mammals and eventual emergence of humans on Earth."