By now, you’re probably sick of hearing about the 2009 H1N1 flu, also known as the swine flu.  But if you believe you’ve had it, and you’ve already recovered from your symptoms, please take a few minutes to complete our new survey.

There have been heard reports of people holding “swine flu parties” in hopes of getting the “mild form” of the H1N1 virus.  But there’s really only one H1N1 virus out there.  Any variability has to do with how people’s bodies are reacting to it. (BTW: The CDC says this is one kind of party you definitely want to skip!)

Some who’ve been infected with H1N1 have suffered from nothing more than a few miserable days stuck in bed.  For others, the virus has caused severe illness resulting in hospitalization and even death.  Some of these differences have to do with age, gender and pre-existing disease burden.

But there are probably genetic factors at work too. A study published just today shows that human cells have proteins that seem to be natural flu fighters.  The researchers who made this discovery suggest that genetic changes that affect the levels of these proteins could determine different levels of vulnerability to the H1N1 virus.

By asking our large and diverse group of customers about their experiences with the flu, and then correlating this information with their genetics, 23andMe hopes to help scientists continue to unravel the mysteries of H1N1.  Genetic markers indicating a propensity for an especially severe reaction to the flu could someday be used to identify people in need of extra attention during outbreaks.  And learning more about the flu in general might lead to new management strategies that could benefit us all.  So please, take a few minutes to answer our H1N1 Survey.

P.S. If you don’t think you’ve had the swine flu this year, don’t worry – there are plenty of other surveys for you to take.  You can always participate in this new survey if you do happen to get sick (though we hope you don’t!).

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Leprosy is a chronic, disabling disease caused by a bacterium (Mycobacterium leprae) that infects only humans and armadillos. The disease affects the skin and peripheral nerves, leading to sores, numbness in the limbs, muscle weakness, and, in severe cases, disfiguring nodules on the skin. Known since biblical times, leprosy was highly stigmatized until the latter part of the 19^th century, when the Norwegian doctor Gerhard Hansen discovered that it was caused by a microorganism.

Although multi-drug therapy has cured millions of people of leprosy in recent decades, hundreds of thousands of new cases still occur per year, mostly in developing countries. Finding a way to eradicate the disease is therefore considered important for reducing the number of preventable disabilities worldwide.

Because Mycobacterium leprae is specific to humans and cannot be grown in lab dishes, research into factors influencing disease susceptibility and clinical outcomes has been limited. But the host environment as well as the bacterium itself can affect the course of the disease; in other words, human genetic factors may play an important role in determining who is more susceptible to infection. Since leprosy has been shown to cluster in families, scientists suspect that much of the variability in disease susceptibility and symptoms stems from diversity in individual human immune systems rather than differences between and within strains of the bacteria.

In a new study published today in New England Journal of Medicine, a team of researchers reports new human genetic factors associated with susceptibility to leprosy in Asians. Led by Fu-Ren Zhang of the Shangdong Academy of Medical Sciences in China and Jian-Jun Liu of the Genome Institute of Singapore, the scientists tested 93 variants across an estimated 50 genes in 3254 Chinese individuals with leprosy and 5955 Chinese individuals without the condition. Their analysis identified variants in seven of these genes to be significantly associated with leprosy.

“The discovery of these genes is a major breakthrough for research in leprosy and infectious diseases in general, and will be significant in the early diagnosis and development of new treatments,” said Dr. Liu in a press release.

The strongest of the associations were rs602875 in HLA-DR-DQ, rs3764147 in C13orf31, and rs9302752 in NOD2. In addition, some of the genetic variants were more strongly associated with a form of leprosy that results in more severe symptoms, known as the multibacillary form. These included rs9302752 in NOD2 and the variant rs1491938 in LRRK2.

(23andMe Complete Edition customers can check their data for SNPs reported in this study using the Browse Raw Data feature. See table at the end of this post.)

Altogether, five of the seven genes identified in the study could be shown to interact biologically in the context of immune response to infection. Two of these five genes, NOD2 and TNFSF15, harbor genetic variants that are also associated with Crohn’s disease (see 23andMe’s report on this condition). Crohn’s manifests some common features with leprosy at the cellular level and other researchers have suggested that mycobacterial infection may be a risk factor for Crohn’s. The findings reported by Zhang and Liu and their colleagues provide additional evidence for shared disease mechanisms between Crohn’s disease and leprosy and may increase the range of treatment options for both conditions.

Variants significantly associated with leprosy in individuals of Asian ancestry

* As reported on the 23andMe website through the Browse Raw Data feature.

** Effect only applicable to the multibacillary form of leprosy. LRRK2 is better known as a susceptibility gene for Parkinson’s disease (see 23andMe’s report on this condition). Interestingly, PARK2, another gene linked to Parkinson’s, was associated with leprosy in earlier studies. The reason for the connection between Parkinson’s and leprosy is unclear, though researchers have speculated that some of the same treatments may be effective for both conditions.

SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.

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Not long after Karl Landsteiner first described the different ABO blood types, scientists started looking for associations between blood type and other human traits.  Some of their theories were truly weird (more on these tomorrow!), but some have held up to scientific scrutiny.

Venous Thromboembolism (VTE)
People with non-type O blood (A, B and AB) have been shown to be at increased risk for VTE.  The reason is thought to be that these people have higher levels of the clot-inducing proteins factor VIII and von Willebrand factor in their blood.  Having non-type O blood further raises the already increased risk for VTE in people who carry the Factor V Leiden and prothrombin G20210A mutations.

Cancer
Since the 1950s, scientists have found that people with type O blood have decreased risk for stomach cancer compared to people with type A.  Other cancers (pancreatic, breast, ovarian, cervical) also occur at lower rates in people with type O blood.  No one is quite sure why this is.  It could be that the sugars found on type A blood cells, which are also expressed by other cells in the body, might somehow help cancers grow more aggressively.  Alternatively, some research has shown that regardless of person’s own blood type, tumors express the type A sugars. In people with type A blood, these sugars go unnoticed by the immune system because they are considered normal.  But in people with type O blood, these new sugars are recognized as foreign, spurring the immune system to destroy the tumors.

Stomach Ulcers
Although stomach cancer is less prevalent in people with type O blood, stomach ulcers are more common in people with this blood type.  The sugars that define the different blood types are also found on cells in the gastrointestinal tract.  Research has shown that these sugars influence the ability of H. pylori, a type of bacteria responsible for a large number of stomach ulcers, to attach to the lining of the stomach.  People with type A or B blood (and hence A or B sugars on their stomach cells) have fewer H. pylori receptors than people with type O.

Severe Malaria
In people infected with malaria, more severe disease is seen in those whose red blood cells are induced to form rosettes, large aggregates that block small blood vessels.  Studies have shown that people with type O blood form fewer, smaller and more easily broken up rosettes than people with type A, B or AB blood.  This is probably because the sugars found on the non-O blood cells end up helping to create larger clumps of cells.

Infectious Disease
Some studies have shown that certain bacterial and viral infections are more or less likely in certain blood types.  For example, type A blood has been linked to a predisposition to “glue ear,” which is caused by infection with Pseudomonas aeruginosa. And some studies suggest that people with type O or B blood are less susceptible to smallpox. The research supporting these and other claims of an impact of blood type on infectious diseases are not as strong as the other associations listed above, however.

(23andMe customers can get a prediction of their ABO blood type based on their DNA data through the new ABO Lab feature.)

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