PHILADELPHIA – For the folks who promote vaccination, these are trying times. Recently, CNN hosted a segment titled: “Virus or Vaccine: Which is Worse?”
It’s enough to set Paul Offit to ranting, which he did this week at a meeting of the Infectious Diseases Society of America. Offit, a physician who heads the infectious disease division at Children’s Hospital of Philadelphia, has devoted a career to fighting illness. In his job, vaccines are often the most reliable weapon available, and cost-effective to boot. And although it’s astonishingly more dangerous to contract a disease than it is to get vaccinated for it, that message seems to have gotten lost somewhere along the way.
Offit traces this detour back to 1982, when DPT — the shot that prevents diphtheria, tetanus and pertussis – was (wrongly) linked to brain damage. “Three people believed their kids were harmed by the vaccine,” he says.
Offit has compassion for families who have a child who has suffered, whatever the cause may be, known or unknown. But since 1982, it’s been one accusation after another against vaccines. People tried to link the HIB vaccine to diabetes (no evidence), the hepatitis B vaccine to multiple sclerosis (all but one study found no link), and other vaccines to SIDS or autism. Recently, the HPV vaccine — which prevents cervical cancer – got linked to heart attacks and strokes (no proof).
And now the seasonal flu vaccine and H1N1 flu vaccine are being skipped by millions of people who somehow distrust the science that went into making them, even though the illnesses they cause can be fatal. Read more »
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Posted in medicalmatrix | February 13, 2010 | 
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In the study, published in the Feb. 15 issue of The Journal of Infectious Diseases, now available online, Jared Baeten and colleagues from the United States and Kenya collected detailed sexual data from a group of male Kenyan truckers and, using statistical models, developed infectivity measures that estimate the per-sexual-act probability of HIV transmission. The study is the first to calculate the probability of infection for men who have multiple, concurrent heterosexual partners, which was found to be significantly higher than infectivity rates calculated in the past from studies of monogamous couples. Their results may help explain the rapid spread of HIV in settings where circumcision is not common and multiple sexual partnerships are.
Between 1993 and 1997, 745 male employees of trucking companies based in Mombasa, Kenya were followed for the study. Initially they were evaluated for circumcision status and HIV-negativity. Over the length of the study the men were asked to give information concerning the number of sexual encounters with three different partner types–wives, casual partners, and prostitutes–and were screened for HIV and other sexually transmitted infections. At the end of the study the probability of infection was calculated using a statistical model that incorporated published data to estimate the rates of HIV infection among the three types of sexual partners.
For the men in the study, the overall probably of becoming HIV-infected following a single act of intercourse was calculated to be .0063, or one in 160. Uncircumcised men had a more than two-fold increased risk of infection per sexual act compared with circumcised men–one in 80 versus one in 200. Read more »
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Background
Mycoplasma species are the smallest free-living organisms. These organisms are unique among prokaryotes in that they lack a cell wall, a feature largely responsible for their biologic properties such as their lack of a reaction to Gram stain and their lack of susceptibility to many commonly prescribed antimicrobial agents, including beta-lactams. Mycoplasmal organisms are usually associated with mucosal surfaces, residing extracellularly in the respiratory and urogenital tracts. They rarely penetrate the submucosa, except in the case of immunosuppression or instrumentation, when they may invade the bloodstream and disseminate to different organs and tissues throughout the body.
Although scientists have isolated at least 17 species of Mycoplasma from humans, 4 types of organisms are responsible for most clinically significant infections that may come to the attention of practicing physicians. These species are Mycoplasma pneumoniae, Mycoplasma hominis, Mycoplasma genitalium, and Ureaplasma species. The focus of this article is infections caused by M pneumoniae; articles on Ureaplasma infections (eg, Ureaplasma Infection) and genital mycoplasmal infections contain discussions of infections caused by other mycoplasmal species.
Pathophysiology
M pneumoniae is perhaps best known as the cause of walking or atypical pneumonia, but the most frequent clinical syndrome caused by this organism is actually tracheobronchitis or bronchiolitis, often accompanied by upper respiratory tract manifestations. Pneumonia develops in only 5%-10% of persons who are infected. Acute pharyngitis and myringitis are less common.
After inhalation of respiratory aerosols, the organism attaches to host cells in the respiratory tract. The P1 adhesin and other accessory proteins mediate attachment, followed by induction of ciliostasis, local inflammation that consists primarily of perivascular and peribronchial infiltration of mononuclear leukocytes, and tissue destruction that may be mediated by liberation of peroxides. Recently, M pneumoniae has been shown to produce an exotoxin that is believed to play a role in the damage to the respiratory epithelium that occurs during acute infection. The organism also has the ability to exist intracellularly. Additionally, acute mycoplasmal respiratory tract infection may be associated with exacerbations of chronic bronchitis and asthma. More extensive information on the pathogenesis of mycoplasmal respiratory infections is available in a recent review article.
Spread of infection throughout households is common, although person-to-person transmission is slower than for many other common bacterial respiratory tract infections; close contact appears necessary. Generally, the incubation period is 2-3 weeks. The organism may persist in the respiratory tract for several months, and sometimes for years in patients who are immunosuppressed, after initial infection. Read more »
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