How exactly was the Irish immigrant known as Typhoid Mary[1] able to infect about 50 people in New York City in the early 1900s without succumbing to the illness herself? Scientists say they are now close to cracking the case.


In a new study, they were able to solve the mystery of how a dangerous bacterial pathogen can, in some people, manage to persist without causing symptoms and find a way to survive for decades.


For the salmonella bacteria that causes typhoid fever, the researchers said it manages to hide in immune cells known as macrophages and "hacks" their metabolism to their own benefit. If the germs are successful in pulling that off, then an infected person can unknowingly spread the pathogen without falling ill themselves -- like in Typhoid Mary, whose real name was Mary Mallon. Just watch the video above.


“To all outward appearances, she was perfectly healthy,” study co-author Dr. Denise Monack, associate professor of immunology and microbiology[2] at Stanford University, said in a written statement.


Monack and her research team infected mice with a strain of salmonella, and found that, the bacteria were able to "wait out" the body's aggressive immune response before they then positioned themselves in the immune cells that became less aggressive at later stages of infection.


“There aren’t a ton of pathogens that hang out in macrophages[3] ,” Monack told the Los Angeles Times, adding that the bacterium behind tuberculosis is another.


So if that's where the nasty germ hangs out, how does it survive and go unnoticed? The researchers found that a protein known as PPAR-delta was required for salmonella to replicate inside the macrophages and "hack" them.


“Salmonella is doing something to activate PPAR-delta,” Monack said in the statement. “We suspect it’s releasing some as-yet-unknown PPAR-delta-stimulating virulence factor into the macrophages it infects. If we can figure out what that is, it could lead to some great anti-salmonella therapeutics with relatively fewer side effects.”


This study was published Aug. 14 in the journal Cell Host & Microbe[4] .



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  • Take A Trip?


    Psychedelics like lysergic acid diethylamide (LSD) have a complicated history of being used as potential treatments for mental illness. Researchers studied <a href="http://query.nytimes.com/gst/fullpage.html?res=950DE6DC1730F931A15757C0A9649D8B63">LSD therapy</a> in the 1950s and 1960s, and published numerous clinical papers involving more than 40,000 patients. The <a href="http://www.fda.gov/regulatoryinformation/legislation/ucm148726.htm">Controlled Substances Act</a> of 1970 then prohibited the drug's medical use.




  • Tapeworm Diet?


    The "<a href="http://articles.latimes.com/2007/feb/19/health/he-esoterica19">tapeworm diet</a>" appeared in the early 20th century. Once thought to be an effective way to lose weight, but some tapeworm species are linked with malnutrition, nausea, vomiting, diarrhea, anemia and other health risks.




  • Medical Vibrators?


    The vibrator emerged as an "<a href="http://www.nytimes.com/books/first/m/maines-technology.html">electromechanical medical instrument</a>" at the end of the 19th century to treat so-called <a href="http://bigthink.com/ideas/18074">female hysteria</a>, of which symptoms included nervousness and trouble sleeping. Advertisements for vibrators could have even been seen in the pages of a Sears, Roebuck and Company catalog.




  • Dog Poop?


    A make-it-yourself remedy to ease a sore throat once included the strange ingredient of Album graecum (which is dried dog dung), as written in the book "<a href="http://books.google.com/books?id=D7KFvTUAVhwC&pg=PA105&lpg=PA105&dq=Album+graecum+sore+throat&source=bl&ots=KMP7gLhMlE&sig=j1aBh7lzrNwhtH1un5A8jVcAEVI&hl=en&sa=X&ei=fJ5gUNOVOarHigK39ICoAQ&ved=0CDcQ6AEwAQ#v=onepage&q=Album graecum sore throat&f=false">The Popularization of Medicine, 1650-1850</a>."




  • Coca-Cola As 'Healthy?'


    Coca-Cola was originally created by <a href="http://voices.yahoo.com/a-quick-history-coca-cola-pepsi-soft-drinks-537657.html" target="_hplink">Dr. John Pemberton around 1886</a> as a "medicinal" formula and marketed as a "health" drink (<a href="http://www.huffingtonpost.com/2011/02/15/coke-recipe-found_n_823552.html">it once contained cocaine</a>, but the ingredient was later removed in 1903). Soda dispensers were even installed in some pharmacies in 1948.




  • Shock & Lobotomy?


    <a href="http://www.nimh.nih.gov/health/topics/brain-stimulation-therapies/brain-stimulation-therapies.shtml">Electroconvulsive therapy</a> (which was first developed around 1938) and <a href="http://scienceblogs.com/neurophilosophy/2007/07/24/inventing-the-lobotomy/">lobotomy</a> (first performed on humans in the 1890s) were both procedures <a href="http://www.apa.org/monitor/2011/02/myth-buster.aspx">thought to "cure" homosexuality</a>. Of course, contemporary science does not classify homosexuality an illness. Electroconvulsive therapy is, however, still a legitimate treatment for severe depression.




  • Smoke For Your Health?


    Before anti-smoking ads became commonplace, there were pro-smoking ads. During the late 19th and early 20th centuries, the inhalation of fumes from burning tobacco was a <a href="http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2844275/">suggested therapy for asthma</a>.




  • Virgin Cleansing?


    The troubling myth that someone infected with a STD can transfer the disease by having sex with a virgin, thus curing themselves, dates back to at least <a href="http://www.thelancet.com/journals/lancet/article/PIIS0140-6736(04)16288-0/fulltext">the 16th Century</a>, when the practice was first documented in relation to syphilis and gonorrhea in Europe. <a href="http://articles.cnn.com/2009-06-04/living/cnnheroes.betty.makoni_1_young-girls-raped-youngest-girl?_s=PM:LIVING">The myth continues</a> in some parts of Africa, leading to many cases of reported child rape.




  • Heroin As Cough Medicine?


    Heroin, chemically known as diacetylmorphine, was once prescribed to treat common ailments such as coughs, colds and pain--the drug was manufactured for such treatment by Bayer starting in 1898, according to <em><a href="http://news.bbc.co.uk/2/hi/uk_news/magazine/4647018.stm">BBC News</a></em>.




  • Ketchup As Medicine?


    In the late 1830s, <a href="http://books.google.com/books?id=e82QWB89_sIC&pg=PA107&lpg=PA107&dq=Dr.+Miles+tomato&source=bl&ots=arnopqhZJW&sig=blTANCDmjbAfY57zjYck2G4dFbU&hl=en&sa=X&ei=supgUITVCYfxiwLb_oDABQ&ved=0CCAQ6AEwAA#v=onepage&q=Dr.%20Miles%20tomato&f=false">Dr. Archibald Miles</a> claimed to have extracted a substance from tomatoes to help ailments such as diarrhea and indigestion. The pills named "<a href="http://www.cleveland.com/taste/index.ssf/2008/08/post.html">Dr. Miles' Compound Extract of Tomato</a>" were later declared a hoax.




  • Ecstasy Therapy?


    The drug <a href="http://www.drugabuse.gov/publications/research-reports/mdma-ecstasy-abuse/brief-history-mdma">MDMA</a> (commonly known as ecstasy) dates back to the early 20th century. During the 1970s, some psychiatrists even suggested using the drug for psychotherapy. Even though the drug is now controlled, proponents of <a href="http://healthland.time.com/2011/02/18/ecstasy-as-therapy-have-some-of-its-negative-effects-been-overblown/">ecstasy therapy have reemerged</a> in recent years.




  • Radium Therapy?


    An advertisement that touts preparing radioactive drinking water at home was one of many promotions for radiation therapy around 1913. Now radium is understood to be a <a href="http://www.epa.gov/rpdweb00/radionuclides/radium.html#affecthealth">health hazard</a>--for example, long-term exposure increases the risk of developing several diseases.




  • Bloodletting?


    Throughout history, <a href="http://www.ncbi.nlm.nih.gov/pubmed/15926663">bloodletting</a> (sometimes with the aid of a leech) was practiced to both cure and prevent illness. But this treatment wasn't all bad--<a href="http://www.msnbc.msn.com/id/5319129/ns/health-health_care/t/fda-approves-leeches-medical-devices/#.UGH6QaRSTox">medical leeches</a> are now sometimes suggested <a href="http://articles.baltimoresun.com/2011-01-23/health/bs-hs-medical-leeches-20110116_1_leeches-medical-devices-medical-science">to help with blood circulation or draining blood</a> during surgeries.




  • Mummy Powder?


    Across medieval Europe and the Middle East, corpses were ground into powder and used as medicine. This "<a href="http://www.aol.com/video/mummy-powder-/517406504/">mummy powder</a>" was thought to cure common ailments, such as <a href="http://io9.com/5917027/powdered-mummy-gladiator-blood-and-other-historical-medicines-made-from-human-corpses">headaches and stomach ulcers</a>.




  • Mercury To Treat Syphilis?


    Mercury was used as a <a href="http://ocp.hul.harvard.edu/contagion/syphilis.html">treatment for syphilis</a> until the early 20th century. Side effects of such mercury treatments could include tooth loss, ulcerations, neurological damage or even death.




  • Shark Cartilage To Treat Cancer?


    The suggestion of using shark cartilage to treat cancer emerged around the 1950s, stemming from research by <a href="http://www.nytimes.com/1998/09/29/nyregion/john-f-prudden-78-surgeon-and-researcher.html">Dr. John Prudden</a>. But recent studies have found no health effects in taking shark cartilage, according to the <a href="http://www.cancer.gov/cancertopics/pdq/cam/cartilage/HealthProfessional/page5">National Cancer Institute</a>.




  • Soothing Syrup?


    Mrs. Winslow's "<a href="http://www.ncbi.nlm.nih.gov/pubmed/11806256">soothing syrup</a>" was a popular formula that emerged in the late 1800s to help ease the teething process for young children. What was in this special syrup? Alcohol and morphine sulfate. The syrup was taken off the market in the 1930s.