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Tuesday, 11 December 2007

US statistics

Arch Intern Med. 2007;167(22):2443-2452.
Trends in Tuberculosis/Human Immunodeficiency Virus Comorbidity, United States, 1993-2004
Rachel Albalak, PhD; Richard J. O’Brien, MD; et al.
Background To our knowledge, this is the first assessment of trends in tuberculosis (TB)/human immunodeficiency virus (HIV) comorbidity in the United States based on national TB surveillance data.
Methods We analyzed all incident TB cases reported to the Centers for Disease Control and Prevention national TB surveillance system from all 50 states and the District of Columbia from 1993 through 2004. Trends in TB/HIV cases were examined according to selected demographic and clinical characteristics.
Results Cases of TB/HIV decreased from 3681 (15% of 25 108 TB cases) in 1993 to 1187 (8% of 14 515 TB cases) in 2004, accounting for 23% of the overall decrease in TB cases during this period. The TB/HIV case rate decreased from 1.4/100 000 in 1993 to 0.4/100 000 in 2004. The highest TB/HIV comorbidity rates persisted in persons aged 25 to 44 years (13.8%), males (9.7%), US-born persons (10.7%), non-Hispanic blacks (17.8%), and persons from the Northeast (11.0%) and the South (10.1%). Propensity stratification, used to account for the unequal probability of patients with TB being tested for HIV during the study period, did not show important differences in TB/HIV comorbidity trends.
Conclusions Comorbidity due to TB/HIV decreased substantially between 1993 and 2004, primarily in US-born persons in states that experienced a TB resurgence between 1985 and 1992. These decreases coincide with improvements in TB control and advances in HIV treatment and diagnosis. The overall decreases obscure the wide variation in comorbidity that exists among some demographic groups and the recent slowing in the decline over the past 3 years.

Sunday, 9 December 2007

More recent history -- Christmas seals

This year the American Lung Association is celebrating 100 years of Christmas Seals® by launching a new Christmas Seals(R) website, "Most Americans alive today have no vivid memories of how widespread deadly tuberculosis was before the 1950s, but it claimed entire families in this country, struck down people from all walks of life, often in their prime."
Jacob Riis, a journalist best known as the author of How the Other Half Lives, pleaded in a newspaper article for someone in America to develop a stamp or seal like the ones he saw being sold in Denmark as a method of raising funds to provide treatment to those without means. Emily Bissell, an American Red Cross volunteer from a prominent Delaware family, took up Riis' challenge. She designed the first Christmas Seal using the American Red Cross proprietary cross and sold them in her local post office. While not a substitute for official U.S. postage, she encouraged people to buy and affix these seals to holiday packages to demonstrate commitment to helping treat tuberculosis. Sales, however, were slow. Leigh Mitchell Hodges, a columnist for the Philadelphia Inquirer, came to the rescue, convincing his editor to run a picture of the seal every day leading up to Christmas and to publish stories about tuberculosis. Buoyed by this publicity, Ms. Bissell succeeded beyond her wildest dreams, and the American Lung Association, then known as the National Tuberculosis Society, gained a means of raising funds.

Saturday, 8 December 2007

BCG Disease

A vaccine meant to protect against tuberculosis is jeopardising the lives of HIV-infected infants, warn experts in a major new report. They call for improvements to vaccination programmes to avoid increasing the health risks for children whose immune systems are weakened by HIV.
The report focuses on how the “global epidemics of HIV and tuberculosis has exploded to create a deadly co-epidemic”, that is rapidly spreading in sub-Saharan Africa. It warns that about a third of the world’s 40 million people with HIV/AIDS are
co-infected with TB, and that the mortality rate these people is five times higher than that for tuberculosis alone.
It also notes that the use of the Bacille Calmette-Guérin (BCG) vaccine against TB in babies with HIV may actually be making the situation worse.
Veronica Miller, a co-author of the report and director of the Washington, DC-based Forum for Collaborative HIV Research, said that there is an "urgent" need for changes to vaccination programmes in sub-Saharan Africa, including improved testing to know whether infants have HIV before vaccinating them against TB.
Live strain
The growing threat of TB and the drug-resistant forms of this bacterial infection that commonly attacks the lungs has increased the need for widespread vaccination, experts say.
Unfortunately, there is a lack of new vaccines against TB, which kills nearly 2 million people each year. For this reason, doctors must rely on the BCG vaccine, developed almost a century ago from a usually non-pathogenic, live strain of Mycobacterium bovis – the cow form of the bacterium that causes TB.
Physicians routinely administer this vaccine to newborns in regions where TB has re-emerged as a threat. This means that millions of infants in developing nations in Africa and Asia receive the vaccine in their first few hours of life.
Unfortunately, though, many of these infants are born with HIV, and subsequently have a weakened immune system. This weakened condition makes them vulnerable to “BCG disease”, a serious illness caused by the M. bovis of the BCG vaccine, which would otherwise not pose a threat.
BCG disease
One recent study conducted in South Africa and published in the journal Clinical Infectious Diseases found that six out of the eight children that became severely ill from the BCG vaccine ultimately died from the M. bovis infection (vol 15, p 559-61). The majority of these children were found to have had HIV.
Miller says that an estimated 600,000 children are born with HIV each year and hundreds are at risk of dying as a consequence of BCG vaccination.
The World Health Organization (WHO) had previously recommended that the BCG vaccine be given to all healthy infants as soon as possible after birth. However, the WHO revised its position and stated in a
May 2007 report that "recent evidence shows that children who were HIV-infected when vaccinated with BCG at birth, and who later developed AIDS, were at increased risk of developing BCG disease."
The report adds that, "among these children, the benefits of potentially preventing severe TB are outweighed by the risks associated with the use of BCG vaccine."
Sophisticated tests
The challenge is to develop more sophisticated HIV tests for newborns, says Miller, who also conducts research at George Washington University in Washington, DC, US. But this will take a bigger financial commitment from governments and aid organisations, she adds.
She explains that the types of HIV tests commonly used in the developing world cannot distinguish the HIV status of infants until they reach about six months of age.
The search for more effective tuberculosis vaccines could produce novel options that avoid the problem of BCG-related illness, says Lewellys Barker at the Aeras Global TB Vaccine Foundation in Rockville, Maryland, US.
He notes that scientists are designing TB vaccines that involve the injection of proteins, as opposed to live bacteria, which would not pose as great a threat to children with HIV.
Journal reference:
HIV-TB Co-Infection: Meeting the Challenge (pdf)

Half a million years

ScienceDaily (Dec. 8, 2007) — Although most scientists believe tuberculosis emerged only several thousand years ago, new research from The University of Texas at Austin reveals the most ancient evidence of the disease has been found in a 500,000-year-old human fossil from Turkey.
The discovery of the new specimen of the human species, Homo erectus, suggests support for the theory that dark-skinned people who migrate northward from low, tropical latitudes produce less vitamin D, which can adversely affect the immune system as well as the skeleton.
Prior to this discovery in western Turkey, which helps scientists fill a temporal and geographical gap in human evolution, the oldest evidence of tuberculosis in humans was found in mummies from Egypt and Peru that date to several thousand years ago.
Paleontologists spent decades prospecting in Turkey for remains of Homo erectus, widely believed to be the first human species to migrate out of Africa. After moving north, the species had to adapt to increasingly seasonal climates.
The researchers identified this specimen of Homo erectus as a young male based on aspects of the cranial suture closure, sinus formation and the size of the ridges of the brow. They also found a series of small lesions etched into the bone of the cranium whose shape and location are characteristic of the Leptomeningitis tuberculosa, a form of tuberculosis that attacks the meninges of the brain.
After reviewing the medical literature on the disease that has reemerged as a global killer, the researchers found that some groups of people demonstrate a higher than average rate of infection, including Gujarati Indians who live in London, and Senegalese conscripts who served with the French army during World War I.
The research team identified two shared characteristics in the communities: a path of migration from low, tropical latitudes to northern temperate regions and darker skin color.
People with dark skin produce less vitamin D because the skin pigment melanin blocks ultraviolet light. And, when they live in areas with lower ultraviolet radiation such as Europe, their immune systems can be compromised.
John Kappelman, professor of anthropology at The University of Texas at Austin, is part of an international team of researchers from the United States, Turkey and Germany who have published their findings in the Dec. 7 issue of the American Journal of Physical Anthropology.
It is likely that Homo erectus had dark skin because it evolved in the tropics, Kappelman explained. After the species moved north, it had to adapt to more seasonal climates. The researchers hypothesize the young male's body produced less vitamin D and this deficiency weakened his immune system, opening the door to tuberculosis.
"Skin color represents one of biology's most elegant adaptations," Kappelman said. "The production of vitamin D in the skin serves as one of the body's first lines of defenses against a whole host of infections and diseases. Vitamin D deficiencies are implicated in hypertension, multiple sclerosis, cardiovascular disease and cancer."
Before antibiotics were invented, doctors typically treated tuberculosis by sending patients to sanatoria where they were prescribed plenty of sunshine and fresh air.
"No one knew why sunshine was integral to the treatment, but it worked," Kappelman said. "Recent research suggests the flush of ultraviolet radiation jump-started the patients' immune systems by increasing the production of vitamin D, which helped to cure the disease."
The Leakey Foundation and the Scientific and Technical Research Council of Turkey funded the research.
Adapted from materials provided by University of Texas at Austin.