In medicine, infectious disease or communicable disease is disease caused by a biological agent such as by a virus, bacterium or parasite. This is contrasted to physical causes, such as burns or chemical ones such as through intoxication.

Basics

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Infectious diseases are the invasion of a host organism by a foreign replicator, generally microorganisms, often called microbes, that are invisible to the naked eye. Microbes that cause illness are also known as pathogens. The most common pathogens are various bacteria and viruses, though a number of other microorganisms, including some kinds of fungi and protozoa, also cause disease. Prions are borderline, and memes would not usually be considered in this scope. An infectious disease is termed contagious if it is easily transmitted from one person to another.

More on [ Infectious disease ]

NEJM — Collection Updates for Infectious Diseases

BOOK REVIEW:
Laboratory medicine has no more urgent role than in the diagnosis and management of infections in immunocompromised patients. For this vulnerable population, clinical algorithms are logically rooted in the need...
ORIGINAL ARTICLE: Evaluation of Universal Antenatal Screening for Group B Streptococcus
Melissa K. Van Dyke, Ph.D., Christina R. Phares, Ph.D., Ruth Lynfield, M.D., Ann R. Thomas, M.D., Kathryn E. Arnold, M.D., Allen S. Craig, M.D., Janet Mohle-Boetani, M.D., Ken Gershman, M.D., William Schaffner, M.D., Susan Petit, M.P.H., Shelley M. Zansky, Ph.D., Craig A. Morin, M.P.H., Nancy L. Spina, M.P.H., Kathryn Wymore, M.P.H., Lee H. Harrison, M.D., Kathleen A. Shutt, M.S., Joseph Bareta, M.P.H., Sandra N. Bulens, M.P.H., Elizabeth R. Zell, M.Stat., Anne Schuchat, M.D., and Stephanie J. Schrag, D.Phil.Background: Group B streptococcal disease is one of the most common infections in the first week after birth. In 2002, national guidelines recommended universal late antenatal screening of pregnant women...
IMAGES IN CLINICAL MEDICINE: Biliary Stones
Ping-Hsien Chen, M.D. and Chiao-Hsiung Chuang, M.D.A 63-year-old woman presented with a 2-day history of fever, abdominal pain, and vomiting. There was no history of previous episodes. Physical examination revealed fever and moderate abdominal tenderness in...

Centers for Disease Control and Prevention

CDC Recommends Shingles Vaccine
People age 60 and older should be vaccinated against shingles, or herpes zoster, a condition often marked by debilitating chronic pain...
New CDC Study Finds Arthritis Can be a Barrier for Adults Seeking to Manage Diabetes through Physical Activity
More than half of adults with diagnosed diabetes also have arthritis, a painful condition that can be a barrier to physical activity—an important health strategy for managing diabetes...
Falls a Leading Cause of Injury-Related Emergency Department Visits for Infants Each Year, CDC Study Shows
Half of the estimated 328,500 infants 12 months of age or younger who were treated for injuries in hospital emergency departments each year from 2001 to 2004 were injured as a result of a fall, according to a study by the Centers for Disease Control and Prevention.

BMC Infectious Diseases - Latest Articles

Use of a T cell interferon gamma release assay in the investigation for suspected active tuberculosis in a low prevalence area
Niclas WinqvistPer BjorkmanAnn NorenHakan Miorner Fri, 03 Jul 2009 00:00:00 -0000
Background: In settings with low background prevalence of tuberculosis (TB) infection, interferon-gamma release assays (IGRA) could be useful for diagnosing active TB. This study aims to evaluate the performance of QuantiFERON(R)-TB Gold (QFT-G) in the investigation for suspected active TB, with particular attention to patients originating in high-incidence countries. Furthermore, factors associated with QFT-G results in patients with active TB were assessed. Methods: From patients investigated for clinically suspected active TB, blood was obtained for QFT-G testing, in addition to routine investigations. Positive (PPV) and negative (NPV) predictive values for QFT-G were calculated, comparing patients with confirmed TB and those with other final diagnoses. QFT-G results in TB patients originating from countries with intermediate or high TB incidence were compared with QFT-G results from a control group of recently arrived asymptomatic immigrants from high-incidence countries. Factors associated with QFT-G outcome in patients with confirmed TB were assessed. Results: Among 141 patients, 41/70 (58.6%) with confirmed TB had a positive QFT-G test, compared to 16/71 (22.6%) patients with other final diagnoses, resulting in overall PPV of 71.9% and NPV of 67.6%. For patients with pulmonary disease, PPV and NPV were 61.1% and 67.7%, respectively, and 90.5% and 66.7% for subjects with extrapulmonary manifestations. Comparing patients from high-incidence countries with controls yielded a PPV for active TB of 76.7%, and a NPV of 82.7%. Patients with confirmed TB and positive QFT-G results were characterized by a lower median peripheral white blood cell count (5.9E9/L vs. 8.8E9/L; P<0.001) and a higher median body mass index (22.7 vs. 20.7; P=0.043) as compared to QFT-G-negative TB patients. Conclusions: The overall PPV and NPV of QFT-G for identifying active TB were unsatisfactory, especially for pulmonary disease. Thus, the usefulness of QFT-G for this purpose is questionable. However, a high PPV was observed for extrapulmonary TB and QFT-G might be considered in the diagnostic process in this situation. The PPV and NPV for identifying active TB among persons originating from regions with high-and intermediate TB incidence was similar to that observed in subjects originating in the low-incidence region.
Role of pathogenic oral flora in postoperative pneumonia following brain surgery
Kinga BagyiAngela HaczkuIldiko MartonJudit SzaboAttila GasparMelinda AndrasiImre VargaJudit TothAlmos Klekner Mon, 29 Jun 2009 00:00:00 -0000
Background: Post-operative pulmonary infection often appears to result from aspiration of pathogens colonizing the oral cavity. It was hypothesized that impaired periodontal status and pathogenic oral bacteria significantly contribute to development of aspiration pneumonia following neurosurgical operations. Further, the prophylactic effects of a single dose preoperative cefazolin on the oral bacteria were investigated. Methods: A matched cohort of 18 patients without postoperative lung complications was compared to 5 patients who developed pneumonia within 48 hours after brain surgery. Patients waiting for elective operation of a single brain tumor underwent dental examination and saliva collection before surgery. Bacteria from saliva cultures were isolated and periodontal disease was scored according to type and severity. Patients received 15 mg/kg cefazolin intravenously at the beginning of surgery. Serum, saliva and bronchial secretion were collected promptly after the operation. The minimal inhibitory concentrations of cefazolin regarding the isolated bacteria were determined. The actual antibiotic concentrations in serum, saliva and bronchial secretion were measured by capillary electrophoresis upon completion of surgery. Bacteria were isolated again from the sputum of postoperative pneumonia patients. Results: The number and severity of coexisting periodontal diseases were significantly greater in patients with postoperative pneumonia in comparison to the control group (p=0.031 and p=0.002, respectively). The relative risk of developing postoperative pneumonia in high periodontal score patients was 3.5 greater than in patients who had low periodontal score (p<0.0001). Cefazolin concentration in saliva and bronchial secretion remained below detectable levels in every patient. Conclusions: Presence of multiple periodontal diseases and pathogenic bacteria in the saliva are important predisposing factors of postoperative aspiration pneumonia in patients after brain surgery. The low penetration rate of cefazolin into the saliva indicates that its prophylactic administration may not be sufficient to prevent postoperative aspiration pneumonia. Our study suggests that dental examination may be warranted in order to identify patients at high risk of developing postoperative respiratory infections.
Truncation in the tcdC region of the Clostridium difficile PathLoc of clinical isolates does not predict increased biological activity of Toxin B or Toxin A.
Ruth MurrayDave BoydMichael MulveyPaul LevettMichelle Alfa Sun, 28 Jun 2009 00:00:00 -0000
Background: The increased severity of disease associated with the NAP1 strain of Clostridium difficile has been attributed to mutations to the tcdC gene which codes for a negative regulator of toxin production. To assess the role of hyper-production of Toxins A and B in clinical isolates of Clostridium difficile, two NAP1-related and five NAP1 non-related strains were compared. Methods: Sequencing was performed on tcdC, tcdR, and tcdE to determine if there were differences that might account for hyper-production of Toxin A and Toxin B in NAP1-related strains. Biological activity of Toxin B was evaluated using the HFF cell CPE assay and Toxin A biological activity was assessed using the Caco-2 Trans-membrane resistance assay. Results: Our results confirm that Toxin A and Toxin B production in NAP1-related strains and ATCC 43255 occurs earlier in the exponential growth phase compared to most NAP1-nonrelated clinical isolates. Despite the hyper-production observed in ATCC 43255 it had no mutations in tcdC, tcdR or tcdE. Analysis of the other clinical isolates indicated that the kinetics and ultimate final concentration of Toxin A and B did not correlate with the presence or lack of alterations in tcdC, tcdR or tcdE. Conclusions: Our data do not support a direct role for alterations in the tcdC gene as a predictor of hyperproduction of Toxin A and B in NAP1-related strains.
Outbreaks of Streptococcus pneumoniae carriage in day care cohorts in Finland - implications for elimination of transmission
Fabian HotiPanu ErastoTuija LeinoKari Auranen Sat, 27 Jun 2009 00:00:00 -0000
Background: Day care centre (DCC) attendees play a central role in maintaining the circulation of Streptococcus pneumoniae (pneumococcus) in the population. Exposure within families and within DCCs are the main risk factors for colonisation with pneumococcal serotypes in DCC attendees. Methods: Transmission of serotype specific carriage was analysed with a continuous time event history model, based on longitudinal data from day care attendees and their family members. Rates of acquisition, conditional on exposure, were estimated in a Bayesian framework utilising latent processes of carriage. To ensure a correct level of exposure, non-participating day care attendees and their family members were included in the analysis. Posterior predictive simulations were used to quantify transmission patterns within day care cohorts, to estimate the basic reproduction number for pneumococcal carriage in a population of day care cohorts, and to assess the critical vaccine efficacy against carriage to eliminate pneumococcal transmission. Results: The model, validated by posterior predictive sampling, was successful in capturing the strong temporal clustering of pneumococcal serotypes in the day care cohorts. In average 2.7 new outbreaks of pneumococcal carriage initiate in a day care cohort each month. While 39% of outbreaks were of size one, the mean outbreak size was 7.6 individuals and the mean length of an outbreak was 2.8 months. The role of families in creating and maintaining transmission was minimal, as only 10% of acquisitions in day care attendees were from family members. Considering a population of day care cohorts, a child-to-child basic reproduction number was estimated as 1.4 and the critical vaccine efficacy against acquisition of carriage as 0.3. Conclusions: Pneumococcal transmission occurs in serotype specific outbreaks of carriage, driven by within-day-care transmission and between-serotype competition. An amplifying effect of the day care cohorts enhances the spread of pneumococcal serotypes within the population. The effect of vaccination, in addition to reducing susceptibility to pneumococcal carriage in the vaccinated, induces a herd effect, thus creating a counter-effect to the amplifying effect of the cohort. Consequently, the critical vaccine efficacy against carriage, required for elimination of transmission, is relatively low. Use of pneumococcal conjugate vaccines is expected to induce a notable herd protection against pneumococcal disease.
Tularemia induces different biochemical responses in BALB/c mice and common voles
Hana BandouchovaJana SedlackovaMiroslav PohankaLadislav NovotnyMartin HubalekFrantisek TremlFrantisek VitulaJiri Pikula Fri, 26 Jun 2009 00:00:00 -0000
Background: Both BALB/c mice and common voles (Microtus arvalis) are considered highly susceptible to tularemia. However, the common vole is reported to harbour Francisella tularensis in European habitats as well as to survive longer with chronic shedding of the bacterium. The purpose of the present study was to compare the response of these two rodents to a wild Francisella tularensis subsp. holarctica strain infection. Methods: Rodents were evaluated for differences in the total antioxidant capacity derived from lowmolecular-weight antioxidants, biochemistry including lipid metabolism, tissue bacterial burdens and histopathology following experimental intraperitoneal infection with 160 colony forming units (CFU) pro toto. Results: Bacterial burdens in common voles started to develop later post-exposure and amounted to lower levels than in BALB/c mice. Elevation of liver function enzymes was more pronounced in mice than common voles and there were marked differences in lipid metabolism in the course of tularemia in these two species. Hypertriglyceridemia and hypercholesterolemia developed in mice, while physiologically higher levels of triglycerides and cholesterol showed a decreasing tendency in common voles. On the other hand, the total plasma antioxidant capacity gradually dropped to 81.5% in mice on day 5 post-infection, while it increased to 130% on day 6 post-infection in common voles. Significant correlations between tissue bacterial burdens and several biochemical parameters were found. Conclusions: As differences in lipid metabolism and the total antioxidant capacity of highly susceptiblerodent species were demonstrated, the role of triglycerides, cholesterol and antioxidants intularemic sepsis should be further investigated.
Allergic sensitisation in tuberculosis patients at the time of diagnosis and following chemotherapy
Linda EllertsenDag StorlaLien DiepKarl BrokstadHarald WikerGeir Hetland Fri, 26 Jun 2009 00:00:00 -0000
Background: It is still a matter of debate whether there is an association between infection with Mycobacterium tuberculosis (M. tuberculosis) and allergy. Previously, we have shown higher levels of specific IgE to different inhalant allergens and total IgE in tuberculosis (TB) patients compared to controls. The objectives of this study were to evaluate a possible change in allergic sensitisation after successful TB treatment and to confirm the finding of our previous study of enhanced allergic sensitisation in TB patients compared to controls in a more controlled setting. Additionally, we wanted to determine the cytokine profile in the same groups and finally to evaluate the association between Bacillus Calmette-Guerin vaccination (BCG) scar and allergic sensitisation among the controls. Methods: Sera were analysed for specific IgE to inhalant allergens (Phadiatop) and total IgE by the use of ImmunoCAP 1000 (Pharmacia Diagnostics). Thirteen different cytokines were also analysed in the sera by multiplex bead immunoassay (Luminex 100, Luminex Corporation), and clinical symptoms of allergy and BCG scar were reported in a questionnaire. Results: A reduction in levels of specific and total IgE were observed after successful TB treatment. TB patients also had higher levels of specific and total IgE compared to healthy controls. Both interleukin (IL)-6 and interferon (IFN)gamma were higher in tuberculosis patients compared to healthy controls. The levels of IL-6 were reduced after successful tuberculosis treatment. The presence of a BCG scar was associated with a reduced risk of developing allergic sensitisation. Conclusions: We observed a reduced level of allergic sensitisation after successful TB treatment. TB patients seem to be more allergically sensitised than healthy controls confirming our previous finding. Furthermore, we observed an inverse association between allergic sensitisation and visible BCG scar, which adds additional support to the hygiene hypothesis.

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