The Ebola outbreak in Guinea, Liberia, and Sierra Leone seems to be subsiding somewhat. The number of new cases is currently running at about 100-150 per week, down sharply from the 800-1,000 cases per week in October-November of 2014. The overall death toll now stands at 10,326 out of 24,907 confirmed cases for a death rate of just over 40%, according to the World Health Organization. There have been only four cases (and one death) in the United States.
Several factors are contributing to the slowing of the outbreak. The virus never went airborne, to the huge relief of health officials. And it turns out that patients are most likely to infect others late in their infection, rather than early. As a result, identifying and isolating infected persons quickly and then tracking down and testing persons with whom they have been in contact has been the key to containment. Getting people to change cultural practices, such as kissing and shaking hands as greetings and washing the dead prior to burial, has slowed the spread of the disease as well.
Nevertheless, it's still too soon to declare the outbreak over. It takes a lot of manpower to find and test all the persons who may have been exposed to someone with the disease, and the three countries with the most cases lack those kinds of resources. Nearly half of all new cases are identified only post-mortem (after death), which makes containment and tracking of exposed persons more difficult.
There are still no cures or effective preventative vaccines for Ebola. Let's hope we can continue to keep this outbreak contained until cures are available.
Saturday, March 28, 2015
Wednesday, March 25, 2015
Horizontal Gene Transfer in Humans
People who worry about genetic modification of organisms by the transfer of genes from another species should know that it happens naturally, even in humans. The transfer of genes from one species to another in nature is called horizontal gene transfer. It's rare, but it does happen.
What's the evidence for interspecies gene transfer? In a paper published recently in Genome Biology, researchers at Cambridge University examined currently available genetic databases of primates (including humans), fruit flies, and nematode worms (the groups were chosen because their genetics are fairly well-known). They then searched the world's known genetic databases for all other organisms for exact matches to specific genes within each group. Matches within a group (e.g. all primates), are most likely to descent from a common ancestor. On the other hand, matches between completely unrelated species (e.g. humans and bacteria), are most likely due to horizontal gene transfer at some time in evolutionary history.
The findings suggested all three groups have picked up genes from totally unrelated species over the long time course of evolution, including genes from algae, fungi, and bacteria. Humans, for example, have picked up more than 145 genes from other species. That's not a lot out of the 20,000 or so in the human genome, but its at least evidence that horizontal gene transfer does occur. Most of these horizontally transferred genes in humans were acquired from bacteria early in human evolution.
Are we better off for it or not? That remains an open question. In terms of the current debate over the safety of genetic engineering, it's worth noting that the natural process is glacially slow compared to the modern purposeful transfer of genes. Still, it's interesting that the process does occur in nature.
What's the evidence for interspecies gene transfer? In a paper published recently in Genome Biology, researchers at Cambridge University examined currently available genetic databases of primates (including humans), fruit flies, and nematode worms (the groups were chosen because their genetics are fairly well-known). They then searched the world's known genetic databases for all other organisms for exact matches to specific genes within each group. Matches within a group (e.g. all primates), are most likely to descent from a common ancestor. On the other hand, matches between completely unrelated species (e.g. humans and bacteria), are most likely due to horizontal gene transfer at some time in evolutionary history.
The findings suggested all three groups have picked up genes from totally unrelated species over the long time course of evolution, including genes from algae, fungi, and bacteria. Humans, for example, have picked up more than 145 genes from other species. That's not a lot out of the 20,000 or so in the human genome, but its at least evidence that horizontal gene transfer does occur. Most of these horizontally transferred genes in humans were acquired from bacteria early in human evolution.
Are we better off for it or not? That remains an open question. In terms of the current debate over the safety of genetic engineering, it's worth noting that the natural process is glacially slow compared to the modern purposeful transfer of genes. Still, it's interesting that the process does occur in nature.
Friday, March 20, 2015
Two New GMO Foods on the Horizon
The latest entries into the genetically modified organisms (GMOs) category are an apple that resists browning when sliced or bruised, and a potato that allegedly produces less of a suspected carcinogen when deep-fried, according to news articles in the New York Times.
The apple is only a modest "improvement". Its ability to resist browning primarily benefits grower, shippers, and sellers by reducing their losses of browned fruit. Secondarily it could open the way to pre-packaged sliced apples in the store, but is that really going to be a big market?
But the potato may be a whole different story, and it may well test the public's understanding of its possible benefits versus the fear some people have of all GMOs. The genetically modified potato contains less of the amino acid, asparagine, according to Simplot, the potato's developer. When heated to very high temperatures such as deep frying, asparagine reacts with sugar to produce acrylamide, a suspected carcinogen. How much asparagine there is in a potato Simplot didn't say, but I suspect it's way less than in most meats. This sounds like making a big deal out of not very much, in an effort to gain widespread acceptance.
An understanding of the word "suspected" is key here. According to the National Cancer Institute, toxicology studies indicate that acrylamide may be a risk for certain cancers in animals, but so far there is no direct link between acrylamide and cancer in humans. There's certainly not enough evidence to ban potato chips and french fries just yet.
How will the market react to the new GMO potato? There have been news reports that McDonalds's has already said it has no current plans to use the new potato. And a genetically modified potato has been tried before; Monsanto pulled its insect-resistant potato from the market after buyers rejected it.
Oh, and by the way, the genetically modified potato does benefit growers, shippers, and retailers, too. Like the apple it resists bruising, so it would reduce annual potato waste by 400 million pounds per year, according to Simplot. I just knew there'd be something in it for Simplot.
The apple is only a modest "improvement". Its ability to resist browning primarily benefits grower, shippers, and sellers by reducing their losses of browned fruit. Secondarily it could open the way to pre-packaged sliced apples in the store, but is that really going to be a big market?
But the potato may be a whole different story, and it may well test the public's understanding of its possible benefits versus the fear some people have of all GMOs. The genetically modified potato contains less of the amino acid, asparagine, according to Simplot, the potato's developer. When heated to very high temperatures such as deep frying, asparagine reacts with sugar to produce acrylamide, a suspected carcinogen. How much asparagine there is in a potato Simplot didn't say, but I suspect it's way less than in most meats. This sounds like making a big deal out of not very much, in an effort to gain widespread acceptance.
An understanding of the word "suspected" is key here. According to the National Cancer Institute, toxicology studies indicate that acrylamide may be a risk for certain cancers in animals, but so far there is no direct link between acrylamide and cancer in humans. There's certainly not enough evidence to ban potato chips and french fries just yet.
How will the market react to the new GMO potato? There have been news reports that McDonalds's has already said it has no current plans to use the new potato. And a genetically modified potato has been tried before; Monsanto pulled its insect-resistant potato from the market after buyers rejected it.
Oh, and by the way, the genetically modified potato does benefit growers, shippers, and retailers, too. Like the apple it resists bruising, so it would reduce annual potato waste by 400 million pounds per year, according to Simplot. I just knew there'd be something in it for Simplot.
Tuesday, March 17, 2015
Bacon and Eggs are Back!
Since the 1960s we've known that high blood cholesterol is a risk factor for atherosclerosis, a disease in which coronary arteries become narrowed by sticky deposits of cholesterol. And so, in an effort to try to keep blood cholesterol within healthy limits, since 1961 the government's dietary guidelines have advised us to avoid high-cholesterol foods such as (bacon and eggs).
That's about to change. In February an influential federal panel of experts that advises the secretaries of Agriculture and Health and Human Services announced that even though high cholesterol is indeed a risk for coronary artery disease, cholesterol derived from dietary sources is not really a significant health risk after all. The panel recommends that cholesterol no longer be called a "nutrient of concern" in the newest version of Dietary Guidelines for Americans, due out later this year.
How did such a complete switch come about? It turns out that the more nutritionists learned about cholesterol, the more they realized that cholesterol is actually an essential nutrient. It is a component of cell membranes, for example. Furthermore, approximately 80% of the cholesterol in your body is synthesized within the body, primarily by the liver. Because only about 20% comes from dietary intake, restricting dietary cholesterol intake is just not a very effective way to lower blood cholesterol levels.
Another significant change in the last fifty years has been the development of effective cholesterol-lowering drug such as Lipitor. Taking a cholesterol-lowering drug is a far more effective way to lower cholesterol than any change in diet.
Finally, experience has shown that when people are asked reduce their intake of one energy-rich food (saturated fats and cholesterol-rich foods, for example), they naturally tend to substitute something else, and oftentimes that something else is sugar. After all, the only three basic choices are fats, sugars, and proteins! And too much sugar isn't good for us, either.
And so once again we can include bacon and eggs in our diet, guilt-free. All things in moderation, of course.
That's about to change. In February an influential federal panel of experts that advises the secretaries of Agriculture and Health and Human Services announced that even though high cholesterol is indeed a risk for coronary artery disease, cholesterol derived from dietary sources is not really a significant health risk after all. The panel recommends that cholesterol no longer be called a "nutrient of concern" in the newest version of Dietary Guidelines for Americans, due out later this year.
How did such a complete switch come about? It turns out that the more nutritionists learned about cholesterol, the more they realized that cholesterol is actually an essential nutrient. It is a component of cell membranes, for example. Furthermore, approximately 80% of the cholesterol in your body is synthesized within the body, primarily by the liver. Because only about 20% comes from dietary intake, restricting dietary cholesterol intake is just not a very effective way to lower blood cholesterol levels.
Another significant change in the last fifty years has been the development of effective cholesterol-lowering drug such as Lipitor. Taking a cholesterol-lowering drug is a far more effective way to lower cholesterol than any change in diet.
Finally, experience has shown that when people are asked reduce their intake of one energy-rich food (saturated fats and cholesterol-rich foods, for example), they naturally tend to substitute something else, and oftentimes that something else is sugar. After all, the only three basic choices are fats, sugars, and proteins! And too much sugar isn't good for us, either.
And so once again we can include bacon and eggs in our diet, guilt-free. All things in moderation, of course.
Monday, March 9, 2015
Oral Immunotherapy to Prevent Peanut Allergies
An early-stage research effort that was discussed on this blog nearly four years ago (see this blog 8/24/2010) has finally borne fruit. In a paper just published in the New England Journal of Medicine, researchers report on the effectiveness of oral immunotherapy (though they don't call it that) in reducing the development of peanut allergies in young children.
It's a particularly well-designed study. The researchers enrolled infants between the ages of 4 and 11 months who were deemed to be at high risk for developing an allergy to peanuts because they had either eczema (a skin condition) or an allergy to eggs. Half of the participants ate at least 6 grams of peanut protein per week until they were five years old; the other half avoided peanut-containing products. Standard skin-prick tests were used to test for sensitivity to peanut protein.
The results were unequivocal; by 60 months of age, 13.7% of the avoidance group but only 1.9% of the peanut-consuming group were allergic to peanuts. In other words, feeding young children peanut protein consistently at an early age reduced the overall incidence of peanut allergy by 86%.
Two important questions are raised by the study. First, if children in the peanut-consuming group were to discontinue consuming peanut protein, would they develop peanut allergies develop later in life, or are they now "cured"? And second, would oral immunotherapy work on older children who already have a peanut allergy?
Perhaps in a couple of years we'll know. But some nutritional therapists are already trying oral immunotherapy on older children who are allergic to peanuts, under close supervision, of course.
It's a particularly well-designed study. The researchers enrolled infants between the ages of 4 and 11 months who were deemed to be at high risk for developing an allergy to peanuts because they had either eczema (a skin condition) or an allergy to eggs. Half of the participants ate at least 6 grams of peanut protein per week until they were five years old; the other half avoided peanut-containing products. Standard skin-prick tests were used to test for sensitivity to peanut protein.
The results were unequivocal; by 60 months of age, 13.7% of the avoidance group but only 1.9% of the peanut-consuming group were allergic to peanuts. In other words, feeding young children peanut protein consistently at an early age reduced the overall incidence of peanut allergy by 86%.
Two important questions are raised by the study. First, if children in the peanut-consuming group were to discontinue consuming peanut protein, would they develop peanut allergies develop later in life, or are they now "cured"? And second, would oral immunotherapy work on older children who already have a peanut allergy?
Perhaps in a couple of years we'll know. But some nutritional therapists are already trying oral immunotherapy on older children who are allergic to peanuts, under close supervision, of course.
Sunday, March 1, 2015
Screening Newborns for Genetic Disorders
Back in 2000, most U.S. states screened newborn infants for just four genetic disorders. Today 42 states screen for at least 29 of the 31 genetic or metabolic disorders for which an Advisory Committee of the Department of Health and Human Services recommends newborns be screened. The list includes cystic fibrosis, sickle cell anemia, hypothyroidism, phenylketonuria, and a host of other conditions so rare you’ve probably never heard of them.
A link to your state's screening programs and tests can be found on the website of the National Newborn Screening and Global Resource Center.
A link to your state's screening programs and tests can be found on the website of the National Newborn Screening and Global Resource Center.
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