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Symbiotic nitrogen (N)‐fixing trees can provide large quantities of new N to ecosystems, but only if they are sufficiently abundant. The overall abundance and latitudinal abundance distributions of N‐fixing trees are well characterised in the Americas, but less well outside the Americas.Here, we characterised the abundance of N‐fixing trees in a network of forest plots spanning five continents, ~5,000 tree species and ~4 million trees. The majority of the plots (86%) were in America or Asia. In addition, we examined whether the observed pattern of abundance of N‐fixing trees was correlated with mean annual temperature and precipitation.Outside the tropics, N‐fixing trees were consistently rare in the forest plots we examined. Within the tropics, N‐fixing trees were abundant in American but not Asian forest plots (~7% versus ~1% of basal area and stems). This disparity was not explained by mean annual temperature or precipitation. Our finding of low N‐fixing tree abundance in the Asian tropics casts some doubt on recent high estimates of N fixation rates in this region, which do not account for disparities in N‐fixing tree abundance between the Asian and American tropics.Synthesis. Inputs of nitrogen to forests depend on symbiotic nitrogen fixation, which is constrained by the abundance of N‐fixing trees. By analysing a large dataset of ~4 million trees, we found that N‐fixing trees were consistently rare in the Asian tropics as well as across higher latitudes in Asia, America and Europe. The rarity of N‐fixing trees in the Asian tropics compared with the American tropics might stem from lower intrinsic N limitation in Asian tropical forests, although direct support for any mechanism is lacking. The paucity of N‐fixing trees throughout Asian forests suggests that N inputs to the Asian tropics might be lower than previously thought. [ABSTRACT FROM AUTHOR]

BACKGROUND: National blood donation screening for West Nile virus (WNV) started in June 2003, after the documentation of WNV transfusion-associated transmission (TAT) in 2002. STUDY DESIGN AND METHODS: Blood donations were screened with investigational nucleic acid amplification assays in minipool formats. Blood collection agencies (BCAs) reported screening results to state and local public health authorities. Donor test results and demographic information were forwarded to CDC via ArboNET, the national electronic arbovirus surveillance system. State health departments and BCAs also reported suspect WNV TATs to CDC, which investigated these reports to confirm WNV infection in blood transfusion recipients in the absence of likely mosquito exposure. RESULTS: During 2003 to 2005, a total of 1,425 presumptive viremic donors were reported to CDC from 41 states. Of 36 investigations of suspected WNV TAT in 2003, 6 cases were documented. Estimated viremia levels were available for donations implicated in four TAT cases; the median estimated viremia was 0.1 plaque-forming units (PFUs) per mL (range, 0.06-0.50 PFU/mL; 1 PFU equals approximately 400 copies/mL). CONCLUSIONS: National blood screening for WNV identified and removed more than 1,400 potentially infectious blood donations in 2003 through 2005. Despite the success of screening in 2003, some residual WNV TAT risk remained due to donations containing very low levels of virus. Screening algorithms employing selected individual-donation testing were designed to address this residual risk and were fully implemented in 2004 and 2005. Continued vigilance for TAT will evaluate the effectiveness of these strategies. [ABSTRACT FROM AUTHOR]

Abstract: Background: The second-generation hepatitis C virus (HCV) enzyme immunoassay (EIA 2), an antibody-detection test, has high sensitivity and is one of the recommended screening tests for detecting HCV infection in the United States. However, its sensitivity among oncology patients is unknown. Objective: Assess the EIA 2 sensitivity among a group of oncology patients at a Nebraska clinic where an HCV outbreak occurred during 2000–2001 using nucleic acid testing (NAT) and recombinant immunoblot assay (RIBA) as the gold standards. Study design: Serum specimens were collected from patients 16 months after transmission had stopped. We tested the specimens using EIA 2 (Abbott HCV EIA 2.0), a NAT assay based on transcription-mediated amplification (TMA) (Gen-Probe TMA assay) and RIBA (Chiron RIBA® HCV 3.0 SIA). HCV infection was defined as a positive RIBA or TMA test in an oncology patient. Alanine aminotransferase (ALT) levels were determined in EIA 2-negative/TMA-positive samples. Results: A total of 264 samples were included in the study. We identified 92 HCV infections, 76 of which were Abbott EIA 2 positive. Abbott EIA 2 sensitivity was 83% (76/92), lower than that reported among healthy adults (90%) (p =0.01) and poor sensitivity was associated with receipt of chemotherapy during the outbreak period (p =0.02). Only 1 (6%) of the 16 EIA 2-negative cases had elevated ALT. Conclusions: In this study, EIA 2 sensitivity among oncology patients was lower than that previously reported among immunocompetent persons. Impaired antibody production related to cancer and/or chemotherapy might explain the reduced sensitivity. These findings indicate that, when assessing HCV status in oncology patients, a NAT test should be routinely considered in addition to EIA. [Copyright &y& Elsevier]