LPA kringle IV type 2 is associated with type 2 diabetes in a Chinese population with very high cardiovascular risk.

The connection between lipoprotein (a) [Lp(a)] levels and the risks of cardiovascular disease and diabetes remains poorly understood. Lp(a) is encoded by the LPA gene, and evidence suggests that the kringle IV type 2 (KIV-2) variant is particularly important to Lp(a) isoform size. A large isoform size, represented as a high number of KIV-2 repeats in LPA, is associated with low serum Lp(a) concentrations and an increased risk of type 2 diabetes. We investigated the associations among Lp(a) concentrations, LPA KIV-2 repeats, and type 2 diabetes in a Chinese population of 1,863 consecutive patients with very high cardiovascular risk, as identified by coronary angiography. Individuals with Lp(a) levels in the top tertile [67.86 (35.34-318.50) mg/dl] had a lower risk of diabetes compared with those in the bottom tertile [7.38 (0.60-12.91) mg/dl]. There was an inverse association between the number of KIV-2 repeats and serum Lp(a) concentrations. This study demonstrated that a high number of LPA KIV-2 repeats are associated with increased risk of type 2 diabetes in a Chinese population with very high cardiovascular risk, which suggests that large Lp(a) isoform size, associated with low Lp(a) concentration, has a causal effect on type 2 diabetes.

Enterovirus 71 encephalomyelitis and Japanese encephalitis can be distinguished by topographic distribution of inflammation and specific intraneuronal detection of viral antigen and RNA.

AIMS: To investigate if two important epidemic viral encephalitis in children, Enterovirus 71 (EV71) encephalomyelitis and Japanese encephalitis (JE) whose clinical and pathological features may be nonspecific and overlapping, could be distinguished. METHODS: Tissue sections from the central nervous system of infected cases were examined by light microscopy, immunohistochemistry and in situ hybridization. RESULTS: All 13 cases of EV71 encephalomyelitis collected from Asia and France invariably showed stereotyped distribution of inflammation in the spinal cord, brainstem, hypothalamus, cerebellar dentate nucleus and, to a lesser extent, cerebral cortex and meninges. Anterior pons, corpus striatum, thalamus, temporal lobe, hippocampus and cerebellar cortex were always uninflamed. In contrast, the eight JE cases studied showed inflammation involving most neuronal areas of the central nervous system, including the areas that were uninflamed in EV71 encephalomyelitis. Lesions in both infections were nonspecific, consisting of perivascular and parenchymal infiltration by inflammatory cells, oedematous/necrolytic areas, microglial nodules and neuronophagia. Viral inclusions were absent. CONCLUSIONS: Immunohistochemistry and in situ hybridization assays were useful to identify the causative virus, localizing viral antigens and RNA, respectively, almost exclusively to neurones. The stereotyped distribution of inflammatory lesions in EV71 encephalomyelitis appears to be very useful to help distinguish it from JE.

Genetic map construction and QTL mapping of resistance to blackleg (Leptosphaeria maculans) disease in Australian canola (Brassica napus L.) cultivars.

Genetic map construction and identification of quantitative trait loci (QTLs) for blackleg resistance were performed for four mapping populations derived from five different canola source cultivars. Three of the populations were generated from crosses between single genotypes from the blackleg-resistant cultivars Caiman, Camberra and (AV)Sapphire and the blackleg-susceptible cultivar Westar(10). The fourth population was derived from a cross between genotypes from two blackleg resistant varieties (Rainbow and (AV)Sapphire). Different types of DNA-based markers were designed and characterised from a collection of 20,000 EST sequences generated from multiple Brassica species, including a new set of 445 EST-SSR markers of high value to the international community. Multiple molecular genetic marker systems were used to construct linkage maps with locus numbers varying between 219 and 468, and coverage ranging from 1173 to 1800 cM. The proportion of polymorphic markers assigned to map locations varied from 70 to 89% across the four populations. Publicly available simple sequence repeat markers were used to assign linkage groups to reference nomenclature, and a sub-set of mapped markers were also screened on the Tapidor x Ningyou (T x N) reference population to assist this process. QTL analysis was performed based on percentage survival at low and high disease pressure sites. Multiple QTLs were identified across the four mapping populations, accounting for 13-33% of phenotypic variance (V (p)). QTL-linked marker data are suitable for implementation in breeding for disease resistance in Australian canola cultivars. However, the likelihood of shifts in pathogen race structure across different geographical locations may have implications for the long-term durability of such associations.

Evaluation of PorB variable region typing of Neisseria gonorrhoeae using PCR-ELISA in samples collected from men who have sex with men.

A polymerase chain reaction (PCR)-based enzyme-linked immunosorbent assay (ELISA) methodology was developed to characterize Neisseria gonorrhoeae porB gene variable regions (VR); the methodology was evaluated in comparison to porB VR typing by checkerboard hybridization. Clinical noncultured samples from 35 men who have sex with men (MSM), positive by nucleic amplification assays for N. gonorrhoeae, were typed using a panel of 40 oligonucleotide probes to porB VRs and compared to checkerboard hybridization. Complete concordance was observed between the two methods at PIB VRs 1, 3, and 7. At the more degenerate VRs 5 and 6, PCR ELISA resulted in obtaining more typeable VRs than checkerboard hybridization due to single nucleotide mismatches. By PCR ELISA, two predominant PIB porB types were identified in 58% of the samples and the remaining 16 samples had one of six other porB types. Both PCR ELISA and checkerboard hybridization methods of porB VR typing allowed characterization of N. gonorrhoeae from noncultured clinical samples including throat and rectal swabs and discriminated N. gonorrhoeae from N. meningitidis present in some of the samples. PCR ELISA is a rapid, relatively inexpensive and alternative molecular typing method for N. gonorrhoeae, suitable for use in conjunction with molecular diagnostic tests.

Topographic changes in SARS coronavirus-infected cells at late stages of infection.

Scanning electron and atomic force microscopy was used for the first time to view the maturation of the severe acute respiratory syndrome-associated coronavirus at the cell surface. The surface form of the cells at advanced infection displayed prolific pseudopodia that, in addition to the rest of the plasma membrane, were also active sites of virus release. High magnification of the maturing virus particles showed a rosette appearance with short knoblike spikes under both the scanning electron and atomic force microscopes. The final expulsion step of the maturing virus particles seemed to result in some disruptions to the plasma membrane. The cytoskeletal network along the edge of the infected cells was enhanced and could be involved in transporting and expelling the progeny virus particles. Thickening of the actin filaments at the cell edge provided the bending force to extrude the virus particles.

The severe acute respiratory syndrome coronavirus in tears.

BACKGROUND: Severe acute respiratory syndrome (SARS) is a new infectious disease that caused a global outbreak in 2003. Research has shown that it is caused by a novel coronavirus. A series of cases is reported where polymerase chain reaction (PCR) testing on tears had demonstrated the presence of the virus. Detection of ocular infection from tears using the PCR technique has been widely used by ophthalmologists to diagnose infections for other viruses. METHODS: This is a case series report from cases classified as probable or suspect SARS cases. Tear samples were collected from 36 consecutive patients who were suspected of having SARS in Singapore over a period of 12 days (7-18 April 2003), and analysed by PCR using protocols developed by the WHO network of laboratories. RESULTS: Three patients with probable SARS (one female and two male patients) had positive results from their tear samples. Tear samples were used to confirm SARS in the female patient, who was positive only from her tears. The positive specimens were found in cases sampled early in their course of infection. CONCLUSIONS: This is the first case series reported with the detection of the SARS coronavirus from tears, and has important implications for the practice of ophthalmology and medicine. The ability to detect and isolate the virus in the early phase of the disease may be an important diagnostic tool for future patients and tear sampling is both simple and easily repeatable. Many healthcare workers are in close proximity to the eyes of patients and this may be a source of spread among healthcare workers and inoculating patients. Ophthalmic practices may need to change as more stringent barrier methods, appropriate quarantine, and isolation measures are vital when managing patients with SARS.

Atypical SARS in geriatric patient.

We describe an atypical presentation of severe acute respiratory syndrome (SARS) in a geriatric patient with multiple coexisting conditions. Interpretation of radiographic changes was confounded by cardiac failure, with resolution of fever causing delayed diagnosis and a cluster of cases. SARS should be considered even if a contact history is unavailable, during an ongoing outbreak.

Proliferative growth of SARS coronavirus in Vero E6 cells.

An isolate of SARS coronavirus (strain 2003VA2774) was obtained from a patient and used to infect Vero E6 cells. The replication cycle of the virus was followed from 1 to 30 h post-infection (p.i.). It was surprising to observe the swift growth of this human virus in Vero cells. Within the first hour of infection, the most obvious ultrastructural change was the proliferation of the Golgi complexes and related vesicles accompanied by swelling of some of the trans-Golgi sacs. Extracellular virus particles were present by 5 h p.i. in about 5 % of the cells and this increased dramatically to about 30 % of the cell population within an hour (6 h p.i.). Swollen Golgi sacs contained virus nucleocapsids at different stages of maturation. These virus precursors were also in large vacuoles and in close association with membrane whorls. The membrane whorls could be the replication complexes, since they appeared rather early in the replication cycle. As infection progressed from 12 to 21 h p.i., the cytoplasm of the infected cells was filled with numerous large, smooth-membraned vacuoles containing a mixture of mature virus and spherical cores. Several of these vacuoles were close to the cell periphery, ready to export out the mature progeny virus particles via exocytosis. By 24 to 30 h p.i., crystalline arrays of the extracellular virus particles were seen commonly at the cell surface.

Hand, foot and mouth disease in Singapore: a comparison of fatal and non-fatal cases.

AIM: An epidemic of hand, foot and mouth disease (HFMD) occurred in Singapore between September and November 2000. During the epidemic, there were four HFMD-related deaths and after the epidemic, another three HFMD-related deaths. This study sought to determine the risk factors predictive of death from HFMD disease. METHODS: The risk factors for fatal HFMD were determined by comparing clinical and laboratory findings between fatal cases (n = 7) and non-fatal controls (n = 131) admitted between September 2000 and April 2001. Enterovirus 71 positive fatal cases (n = 4) and non-fatal controls (n = 63) were also compared. RESULTS: In total, 138 HFMD cases with a mean age of 32 mo were studied. The majority of fatal cases died from interstitial pneumonitis, of whom three also had brainstem encephalitis. Of the 131 non-fatal cases, 3 had concomitant infections (respiratory syncytial virus bronchiolitis, right-sided pneumonia, Haemophilus influenzae type b meningitis), 2 had aseptic meningitis, and 1 each had transient drowsiness, intravenous immunoglobulin-related complications and transverse myelitis. By multivariate logistic regression analysis, atypical physical findings (p = 0.0006), raised total white cell count (p = 0.0128), vomiting (p = 0.0116) and absence of mouth ulcers (p = 0.043) were predictive of a fatal course. Although previous epidemics have described neurogenic pulmonary oedema as the main cause of death, the fatal cases in this study died mainly from interstitial pneumonitis alone or with myocarditis or encephalitis. CONCLUSION: Although HFMD is generally a benign disease, risk factors such as vomiting, absence of mouth ulcers, atypical presentation and raised total white cell count should alert the physician of a fatal course of illness.

Early events of SARS coronavirus infection in vero cells.

An isolate from a patient in the recent severe acute respiratory syndrome (SARS) outbreak in Singapore was used to infect Vero E6 cells. This study concentrated on the first 30 min of infection. It was discovered that the SARS coronavirus attached, entered, and uncoated the nucleocapsids, all within a 30-min period. At 5 min after infection, several virus particles lined the Vero cell plasma membrane. Virus particles were at various stages of fusion at the cell surface, since entry was not a synchronised process. After entry (10 and 15 min), spherical core particles moved into the cytoplasm within large vacuoles. Quite surprising at such early stages of infection (20 min), a virus-induced change in the infected cells was evident. The induction of myelin-like membrane whorls was obvious within the same vacuoles as the core particles. The significance of this virus-induced change is unknown at this stage. By 25-30 min postinfection (p.i.), the spherical core particles appeared to be disassociating and, in their place, doughnut-shaped electron-dense structures were observed. These could be the virus genomes together with the helical nucleocapsids. They were no longer in large vacuoles but packaged into smaller vacuoles in the cytoplasm, and occasionally in small groups.

Clinical characteristics of an outbreak of hand, foot and mouth disease in Singapore.

BACKGROUND: We experienced a hand, foot and mouth disease (HFMD) outbreak in late year 2000 in Singapore. Between 14 September 2000 and 14 November 2000, a total of 3526 cases of HFMD were notified. There were 652 patients clinically suspected to have HFMD, who were seen at the Children's Emergency department of KK Women's and Children's Hospital of Singapore. OBJECTIVE OF THE STUDY: To study the clinical profile and virologic isolates of children admitted with HFMD during the outbreak. STUDY DESIGN: A prospective observational study. METHODS: Analysis of clinical features and virologic studies of 129 selected cases of HFMD and herpangina. RESULTS: The median age was 25 months with a range of between 4 months and 11 years. The majority were less than 5 years old (87%). The male-to-female ratio was 1.3:1. The median numbers of day of illness to presentation to the hospital was 3 days. Poor feeding and loss of appetite accounted for 76.7% of the admissions. Symptoms of vomiting were present in 37.2% of the cases. Oral ulcers were found in 96.1%, rashes over hands in 87.6%, over feet in 86.8% and over buttocks in 54.3%. Only 4.7% exhibited no rashes other than oral ulcers and were labelled as herpangina. The median duration of fever was 3 days, ranging from 2 to 7 days. An intravenous drip was required in 68.2% due to poor feeding. Viral cultures were sent in 89.1% of patients of whom 61.7% of patients were positive for viruses. Of the positive cultures, types of viruses isolated were EV71 (enterovirus 71) in 59/71 (83%), Coxsackievirus (A16, A24, A2 B3, B4) in 6/71 (8.4%), EV Untypable in 4/71 (5.6%) and mixed [EV71, echo25, cytomegalovirus (CMV)] in 2/71 (2.8%). EV71 was isolated mostly from stool samples followed by vesicle fluid culture and throat swabs. Two siblings aged 14 months and 2.5 years died during this period at day 5 of illness, their post-mortem examinations showed interstitial pneumonitis of the lungs. EV71 was isolated from the brain, heart, tonsils, intestines, throat and rectal swabs. A raised total white cell count of 14,000/L versus 12,000/L was significantly associated with complicated HFMD (P = 0.04). There was no difference in clinical characteristics of EV71 versus non-EV71 infections. Other viral illnesses, e.g. measles and CMV, may be mistaken for HFMD in the outbreak setting. CONCLUSIONS: HFMD tends to occur in younger children less than 5 years old due to low herd immunity. Poor feeding due to mouth ulcers accounts for admission to hospital requiring intravenous drip. EV71 accounted for the majority (75%) of the positive isolations, followed by coxsackievirus and untypable EV, mixed infection of echovirus or CMV. The yield of virus isolation was highest from stool, followed by vesicles and throat swabs. There is no difference in clinical characteristics of EV71 and non-EV71 virus infections. Enterovirus can cause mild symptoms to fatal death. Two infants died of interstitial pneumonitis and encephalitis.

Late clinical and magnetic resonance imaging follow up of Nipah virus infection.

The Nipah virus is a newly identified paramyxovirus responsible for an outbreak of fatal encephalitis in Malaysia and Singapore. This paper reports the follow up clinical and magnetic resonance imaging findings in 22 affected subjects. Of 13 patients with encephalitis, one died, one was lost to follow up, and seven recovered. Among the four remaining patients, one had residual sixth nerve palsy, another suffered from severe clinical depression, and a third patient had evidence of retinal artery occlusion. One patient with delayed onset Horner syndrome had a single lesion in the cervical spinal cord. The brain magnetic resonance findings were stable or improved in nine patients over 18 months of follow up. Among a second group of nine asymptomatic seropositive abattoir workers, magnetic resonance examination in seven subjects revealed discrete small lesions in the brain; similar to those detected in encephalitis patients. These findings suggest that in addition to encephalitis, the newly discovered Nipah virus affects the spinal cord and the retina. Late clinical and radiological findings can occur in Nipah virus infections as with other paramyxoviruses.

A survey of Nipah virus infection among various risk groups in Singapore.

Following the Nipah virus (NV) outbreak in March 1999 in Singapore, a serological survey was undertaken to screen individuals potentially exposed to NV. Blood samples were tested for NV IgM, IgG and neutralizing antibodies. Twenty-two (1.5%) of 1469 people tested had antibodies suggesting NV infection. Although 12 of the 22 infected people (54.6%) were symptomatic, the remaining 10 (45.4%) were clinically well and had no past history of compatible pulmonary or neurological disease. Clinical and serological findings suggested three people had been infected with NV before the outbreak was recognized. All those who were infected were male abattoir workers. None of the people who had contact with horses, and no healthcare workers exposed to infected patients and their specimens had detectable antibodies. This study provides evidence that NV causes asymptomatic infection. All of the antibody positive individuals had direct contact with pigs and there was no evidence of human to human transmission.

Aseptic meningitis in children--the Singapore experience.

OBJECTIVE: To study the incidence, aetiology, clinical characteristics and management of paediatric aseptic meningitis in a paediatric hospital in Singapore. MATERIALS AND METHODS: Patients with cerebrospinal fluid (CSF) pleocytosis, a negative Gram stain and bacterial culture were reviewed retrospectively from 1 January to 31 December 2000. Eighty-seven patients who fulfilled the criteria for aseptic meningitis and without neurological deficits were studied. In addition, reverse transcriptase polymerase chain reaction (RT-PCR) using pan enterovirus primers was subsequently performed on 73 of these CSF specimens which were available for storage. RESULTS: The incidence of aseptic meningitis was approximately 37 cases per 10,000 admissions. Non-polio enteroviruses were isolated from 29 of 64 (45.3%) CSF and 38 of 52 (73.1%) stool samples. RT-PCR was positive in 43 (58.9%) of the archived CSF specimens. The aetiologies of the remaining cases were mostly unidentified. Their ages ranged from 5 days to 12 years (median, 2 months). All patients except 1 had fever. Vomiting or poor feeding occurred in 44.7%, cough or running nose in 35.3%, irritability was observed in 35.3%, seizures in 7.1%, a rash in 10.6% and diarrhoea in 5.9%. All patients recovered without sequelae. The median CSF white cell count was 212 cells/mm3 (range, 7 to 12,000). The median glucose concentration was 2.7 mmol/L (range, 1.6 to 4.4). The median CSF/blood glucose ratio was 0.52 (range, 0.23 to 0.73). Median length of stay was 7 days (range, 4 to 17). Eighty-four patients (96.6%) received antibiotics for a median of 5.5 days (range, 2 to 14). CONCLUSION: Enteroviruses were the most common aetiologic agent identified. A method of early diagnosis using RT-PCR for enteroviruses is necessary to reduce the current duration of antibiotic usage and to decrease the length of hospital stay.

Prevention of human immunodeficiency virus (HIV) transmission from mother to child--a cohort study in Singapore.

INTRODUCTION: The landmark Paediatric AIDS Clinical Trials Group (PACTG) trial 076 showed in 1994 that antiretroviral therapy (ART) was effective in reducing maternal-child transmission of human immunodeficiency virus (HIV). This trial included antenatal oral zidovudine (ZDV), intrapartum intravenous ZDV, 6 weeks of oral ZDV to the babies and no breastfeeding. MATERIALS AND METHODS: This study is an on-going, prospective, open-label trial conducted from 1995 in which we enrolled HIV-infected pregnant women using the above strategy. Since 1997, the antenatal component of the regimen was modified to include lamivudine with ZDV. All babies had serial HIV polymerase chain reaction (PCR) and antibody tests including enzyme-linked immunosorbent assay (EIA), particle agglutination (PA) and Western blot (WB) at day 1, 1 week, 1, 2, 3, 6, 12 and 18 months. RESULTS: A total of 16 out of 19 eligible women were recruited from 1995 to 1999. The median age was 26 years (range 22 to 38 years), 38% were Singaporeans, median CD4 was 421 cells/mL (range 18 to 713 cells/mL) and median baseline gestational age was 23.5 weeks (range 8 to 32 weeks). None of the 16 children was infected as evidenced by 2 negative HIV PCRs including 1 done > 4 months old with a follow-up of 6 months to 2 years. There was a statistically significant difference between the 3 HIV antibody tests at 12 months of age (P = 0.003), there being more negative results with WB as compared to PA (P = 0.02). However, the difference between the 3 tests at 18 months was not statistically significant. No long-term side effects in these children were seen. CONCLUSION: Although the number of patients in this study is small, the absolute prevention of transmission (95% confidence intervals 0%-17%) in this cohort supports the recommendation of antenatal HIV screening and treatment of those infected.

Alteration of virus entry mode: a neutralisation mechanism for Dengue-2 virus.

Polyclonal antibodies derived from dengue virus immune sera and 3H5 monoclonal antibody showed potent neutralisation effect on dengue-2 virus in the plaque reduction neutralisation assay. This study demonstrated that antibodies present in immune human sera and 3H5 monoclonal antibody neutralised dengue-2 virus by altering the virus entry pathway into cells. In the presence of neutralising antibodies, dengue-2 virus was endocytosed by LLC-MK2 cells. The endocytosis process involved ruffling of antibody-coated virions by cellular pseudopodia and invagination of cell membrane. This mode of entry is atypical as compared to direct fusion of dengue-2 virus with cell membrane in the absence of antibody. The virions were internalised in the form of virion-antibody complexes consisting of single or clumps of virions. After 3 minutes of incubation, neutralised virions were detected in cellular vesicles, and signs of intra-endosomal penetration into cytoplasm were not evident even after a prolonged incubation of 10 minutes, suggesting that viral uncoating was compromised. Vesicle-bound virions were no longer detected after 20 minutes of incubation. In addition, no sign of viral replication was detected in cells infected with "neutralised" virions by immunofluorescence assay. This indicated that internalised virions had been degraded leading to abortive infection. In conclusion, antibodies present in 3H5 monoclonal antibody and human immune sera rendered dengue-2 virus non-infective by neutralising the viral fusion site and causing alteration of viral entry mode. Antibodies in immune sera but not 3H5 monoclonal antibody also exerted minimal inhibitory effect on virus binding and internalisation.

RT-PCR, nucleotide, amino acid and phylogenetic analyses of enterovirus type 71 strains from Asia.

A specific and sensitive method based on RT-PCR was developed to detect enterovirus 71 (EV71) from patients with hand, foot and mouth disease, myocarditis, aseptic meningitis and acute flaccid paralysis. RT-PCR primers from conserved parts of the VP1 capsid gene were designed on the basis of good correlation with sequences of EV71 strains. These primers successfully amplified 44 strains of EV71 including 34 strains isolated from Singapore in 1997 and 1998, eight strains from Malaysia isolated in 1997 and 1998, one Japanese strain and the neurovirulent strain EV71/7423/MS/87. RT-PCR of 30 strains of other enteroviruses including coxsackievirus A and B, and echoviruses failed to give any positive amplicons. Hence, RT-PCR with these primers showed 100% correlation with serotyping. Direct sequencing of the RT-PCR products of 20 EV71 strains revealed a distinct cluster with two major subgroups, thus enabling genetic typing of the viruses. The genetic heterogeneity of these strains culminated in amino acid substitutions within the VP1, VP2 and VP3 regions. The sequencing of a 2.9 kb fragment comprising the capsid region and the major part of 5' UTR of two Singapore strains revealed that they belonged to a group distinct from the prototype EV71/BrCr strain and the EV71/7423/MS/87 strain. The dendrogram generated from 341 bp fragments within the VP1 region revealed that the strains of Singapore, Malaysia and Taiwan belong to two entirely different EV71 genogroups, distinct from the three genogroups identified in another recent study.

Failure of routine HIV-1 tests in a case involving transmission with preseroconversion blood components during the infectious window period.

CONTEXT: Current screening practices for blood donations have been successful in reducing human immunodeficiency virus (HIV) transmission through receipt of contaminated blood products. However, HIV-infected blood donations made prior to seroconversion and before high levels of viral replication occur could test negative using both serologic antigen and antibody tests. Testing based on nucleic acid amplification (NAT) is being implemented to screen for HIV-infected blood donated during this period, yet the issue of single vs minipool donation screening remains unresolved. OBJECTIVES: To determine HIV-1 genetic linkage between virus in 2 HIV-1-infected recipients of blood components and virus in the donor, who was HIV antigen and antibody negative at the time of donation; to screen the blood donor's plasma with HIV NAT assays, including those currently proposed for use in US blood donation screening. DESIGN AND SETTING: Case study conducted in October 1997 involving the Communicable Disease Centre, Singapore General Hospital, and the Singapore Blood Transfusion Service, Singapore. SUBJECTS: The blood donor and the 2 recipients of donor platelets and red blood cells. MAIN OUTCOME MEASURES: Genetic analysis of the HIV-1 p17 coding region of gag and the C2V5 region of env to determine the genetic relatedness of virus from the donor and recipients; reactivity in quantitative and qualitative assays, and reactivity in donor screening HIV NAT assays in single donation and minipool screening contexts. RESULTS: Direct DNA sequencing demonstrated identical HIV-1 subtype E viral sequences in the donor and recipients. Based on comparisons of a qualitative and quantitative assay for HIV-1 RNA levels, a low level of viremia (range, 5-39 copies/mL in plasma) was estimated to be in the donor's undiluted blood at the time of donation. Additional testing using donor-screening NAT assays showed consistent detection of HIV RNA in the undiluted donor plasma whereas detection was inconsistent at the 1:16 and 1:24 dilution levels currently used in minipool screening of blood donations in the United States. CONCLUSIONS: Transmission of HIV from a blood donor to a platelet recipient and a red blood cell recipient occurred in the preseroconversion infectious window period. The viral load in the implicated donation was estimated to be less than 40 copies/mL of plasma. Current US minipool HIV NAT screening protocols may not be sufficiently sensitive to detect all infectious window-period donations. JAMA. 2000;284:210-214