General Epidemiology
tsmith | April 6, 2006 Again on the zoonoses topic, today's BBC news has an article about cats and "bird flu" (referencing this article in Nature).
The first report of domestic cats dying of the H5N1 virus emerged in Thailand in 2004 when 14 out of 15 cats in a household near Bangkok fell ill and died.
One had eaten a chicken carcass on a farm where there was an outbreak of the virus.
Post-mortem examinations on three of the cats confirmed the presence of H5N1.
Since then, there have been deaths among cats in Indonesia, Thailand and Iraq, where H5N1 appears to be prevalent among poultry.
And the disease is…
tsmith | April 6, 2006 Last week's Nature had an article on yet another example of poor design: mitochondrial diseases. Mitochondria are the organelles within eukaryotic cells that provide the energy for the cells. Once free-living bacteria, the precursors of mitochondria were engulfed by larger cells billions of years ago. Since that time, mitochondria have lost much of their genome--only 37 genes remain in human mitochondria. Many have ended up in the host nucleus, leaving the mitochondria dependent on the host cell for much of their processes.
Mutation rates of mitochondrial genes are 10-20 times higher…
tsmith | April 5, 2006 As I mentioned in previous posts, the emergence of new infectious--especially zoonotic--disease isn't limited to poor countries. Exact numbers vary depending on whose estimates you use, but this source puts the number of pet dogs in the United States alone at roughly 63 million, with over 76 million pet cats. This source is almost 10 years old and thus outdated, but we can use it as a ballpark: it claims almost 100 million cattle and calves in the U.S. Similarly, over 60 million hogs; almost 8 million sheep; 2.5 million horses and ponies; 366 million chickens. We have a lot of animals…
tsmith | April 5, 2006...but just haven't had the time to do more extensive write-ups. So, a mini carnival of good stuff:
First, as other Sciencebloggers have noted, Seed is sponsoring a writing contest. $1000 dollar top prize and publication in Seed to the winner.
Cervantes at Stayin' Alive writes about the cost of pandemic preparedness--you might be surprised that it's, well, nothing so far. You get what you pay for?
Joseph has a post on Ebola examining the claims made by Eric Pianka that have received so much attention lately.
Some Ohio infectious disease news: tuberculosis found in illegally-transported…
tsmith | April 4, 2006In addition to all the science of H5N1, several presentations were given discussing communication between scientists and the public (or those who more often communicate with the public--science journalists). As I've written on here before, it's not an easy dance to figure out, for a variety of reasons discussed below.
As anyone who follows science reporting in the mass media knows, it can seem at times that each new study contradicts the last. Something is good for you; yesterday it was bad for you. Something is the new treatment of tomorrow based on early studies; but sorry, it was…
tsmith | April 4, 2006 I mentioned last week that Iowa's suffering from a large outbreak of mumps. An update, from the March 30th Morbidity and Mortality Weekly Report:
In the United States, since 2001, an average of 265 mumps cases (range: 231--293 cases) have been reported each year,* and in Iowa, an average of five cases have been reported annually since 1996. However, in 2006, by March 28, a total of 219 mumps cases had been reported in Iowa, and an additional 14 persons with clinically compatible symptoms were being investigated in three neighboring states (11 in Illinois, two in Nebraska, and one in…
tsmith | April 4, 2006Busy yesterday and today, but I saw a brief mention of a study yesterday that Orac has discussed in more detail today. The study questions whether an "autism epidemic," as frequently cited in the anti-vaccination literature, has really occurred in the United States or not.
So, in nearly all states, as the reporting of autism cases for special education administrative purposes increased, the reporting of mental retardation and learning disabilities declined correspondingly, suggesting that children who once would have been classified as mentally retarded or learning disabled were now more…
tsmith | April 3, 2006 As conferences covering both emerging infectious diseases and emerging zoonoses, influenza H5N1 was obviously a prominent topic of discussion. The big question wasn't really answered--what is the most important mechanism of spread from country-to-country: wild birds, or domestic poultry? The only thing that was clear is that the answer, well, isn't. I know grrlscientist has written extensively about the evidence against wild birds as a vector (using search word "influenza" here brings up many of them; more on her old site), and there certainly was a lot of discussion about farming and…
tsmith | April 2, 2006 Joseph over at Immunoblogging has two posts on Mycobacterium bovis and gives a potential answer to Dave S.'s question here. In post one, Joseph notes (after the fold):
It's interesting to note that Mycobacterium bovis, which infects farmed animals dates back roughly to the time we domesticated animals proving that for a change, we gave one of our pathogens to an animal and not the other way around.
In part two, Joseph discusses mycobacteria in general, and why M. bovis is a threat to farm economies.
Part three discusses the role badgers play (or don't) in the transmission of M. bovis to…
tsmith | April 1, 2006At the risk of starting an infectious cancer/HIV/AIDS fight over at The Loom, I'll point your attention to Carl's post discussing, well, those topics here. He elaborates on a study I mentioned here but didn't delve very much into the science. Zimmer does--check out the link to find out how he relates it to HIV.
tsmith | March 31, 2006 So far this week, I've mostly been talking in generalities--the introductions to the topic, or how the animals we eat or other types of human behavior can put us at greater risk for the emergence of such diseases. Today I want to talk about a more specific example: an ongoing outbreak of a virus called chikungunya.
Chikungunya (from the Swahili word for "stooped walk," or "that which bends up" depending on who you believe, referring to the posture of a person suffering from the disease) is an arbovirus: a virus that is transmitted by insects. In this case, the insect in question is the…
tsmith | March 29, 2006From the Bushmeat Task Force:
In Africa, forest is often referred to as 'the bush', thus wildlife and the meat derived from it is referred to as 'bushmeat'. This term applies to all wildlife species, including threatened and endangered, used for meat including: elephant; gorilla; chimpanzee and other primates; forest antelope (duikers); crocodile; porcupine; bush pig; cane rat; pangolin; monitor lizard; guinea fowl; etc.
Some of this can be hunted legally--much of it is not. Though I won't be concentrating on the bushmeat crisis per se (the focus of the Bushmeat Task Force), they note several…
tsmith | March 28, 2006I mentioned previously that a new virus had been found that's associated with prostate cancer. Several ongoing studies are finding tons of new species of microbes, and we're learning more about the diversity that is around us every day. And though most of these newly-discovered organisms won't harm us, some just might.
A new study (summarized here points to a calicivirus (genus Vesivirus, a relative of the Norovirus that has gotten much attention recently as the cause of gastroenteritis on cruise ships) as a potential cause of human illness. Vesivirus has an oceanic reservoir and has…
tsmith | March 28, 2006I'd like to continue the overview of emerging infectious diseases (part one is here) by discussing some reasons why diseases "emerge." Obviously, this will be somewhat of a simplification; many diseases may emerge due to a combination of the topics mentioned below, or may have factors involved that I don't mention, so these should be considered broad categories rather than an all-inclusive list.
So, one reason: climate change. An obvious example of this are diseases borne by arthropods, which live in a fairly narrow range of temperatures or environments. Global warming or cooling may…
tsmith | March 27, 2006Sometimes amid all the news about H5N1, the "old and boring" diseases get overlooked, such as chickenpox and mumps.
State health officials said they are concerned about a rare strain of virus behind an outbreak of 60 mumps cases in Iowa.
Mary Gilchrist, director of the state's University Hygienic Laboratory, said the genotype G strain is infrequently seen in the United States. With the number jumping from 17 cases just two weeks ago, she predicted there could be more outbreaks this spring.
"If the past predicts the future, it will get worse in April," she said.
(Continued below)
Recall that…
tsmith | March 27, 2006Part One: Introduction to Emerging Diseases and Zoonoses
Part Two: Introduction to Emerging Diseases and Zoonoses continued
Part Three: Bushmeat
Part Four: War and Disease
Part Five: Chikungunya
Part Six: Avian influenza
Part Seven: Reporting on emerging diseases
Part Eight: Disease and Domesticated Animals
Part Nine: The Emergence of Nipah Virus
Part Ten: Monkeypox
Part Eleven: Streptococcus suis
Part Twelve: Salmonella and fish
Part Thirteen: new swine influenza virus detected
Part Fourteen: dog flu strikes Wyoming.
Part Fifteen: Clostridium species.
Part Sixteen:…
tsmith | March 26, 2006Over at Good math, bad math, Mark has a bit more on mathematical modeling. Before anyone screams "witch hunt," please note:
I'll leave the science debate over at Aetiology, where it belongs. But there's definitely a mathematical aspect to this. Professor Culshaw lends her authority as a mathematician to the HIV denialist folks. Does her math support what she's saying?
Alas, no.
Professor Culshaw is not a bad mathematician - quite the opposite. What I can read of her publications shows very solid mathematical work, done extremely well.
The problem is that when she tries to apply the…
tsmith | March 24, 2006Actually being at a conference soaking up so much of this stuff means, alas, not nearly as much time as I usually spend during the week actually reading the new literature in many of the areas I write about. Over at Effect Measure, as usual, they help to make up for that, by commenting on two new papers in Science and Nature that give one potential reason why human-to-human transmission isn't occurring yet--but Revere notes it's not quite that simple.
(More after the jump)
The reason, the researchers propose, is that the cells bearing the type of receptor the avian virus is known to favor…
tsmith | March 18, 2006 I discussed the so-called "cervical cancer vaccine," a multivalent vaccine protective against several strains of the human papilloma virus previously here. In the new issue of the New England Journal of Medicine, there's aperspective on the vaccine, and issues surrounding it:
Genital HPV infection is common, with an estimated 6.2 million new infections each year in the United States. Although most infections are asymptomatic and transient, persistent infection with oncogenic HPV types is a serious health issue. Cervical cancer is the 11th most common cancer among women in the United States…
tsmith | March 17, 2006 Is Crohn's disease caused by Mycobacterium avium pseudotuberculosis (MAP)?
In an article out yesterday, Australian Dr. Thomas Borody claims yes, and that the medical community is simply too "stuck in their ways" to admit it. I explain below why I think this is incorrect--or at least, premature.
I mentioned several times in the various AIDS threads and in the prostate cancer/virus thread that it's often difficult to determine an infectious cause of a so-called "chronic" disease. Not only is there generally a time lag between infection and disease development, but it may be that only…