Experimental determinations of the detection efficiency for positrons impacting a channel electron multiplier with incident energies between 0–1400 eV are presented. A log-normal dependence with energy is established and used to compute the positron-to-positronium detection efficiency ratio as a function of positronium energy, as required for determining quantities involving the ratio of positron and positronium rates. A log-normal energy-dependence is also observed in results of previous work with electrons, protons and ions.

Background While syphilis transmission is increasing, precisely how Treponema pallidum is transmitted sexually is unclear. This study of MSM with early syphilis determined the frequency of Treponema pallidum shedding from potentially asymptomatic sites and the stage with the most frequent shedding. Methods MSM were recruited between 2015 and 2019, at Melbourne Sexual Health Centre, Australia. Men were eligible if they reported sex with men during the previous year, were aged ≥18 years and had laboratory-confirmed primary, secondary, or early latent syphilis. All syphilis lesions were swabbed. Non-lesion samples collected were oral rinse, oral cavity swab, anal canal swab, urine, and semen. Specimens were tested for T. pallidum using two PCR assays. Results 200 men with serologically-confirmed early syphilis were included: 54 (27%) primary, 93 (46·5%) secondary and 53 (26·5%) early latent cases. T. pallidum DNA was detected orally in 48 (24%; 95% CI: 18.3–30.5%) men by oral rinse and/or oral lesion swab, 24 with no oral lesion. Oral T. pallidum detection was most frequent during secondary syphilis compared to other stages, (44%(41/93) versus 7% (7/107), p <0·0001); and in men with RPR titres ≥1:64 (32% (37/117) versus 13% (11/83), p = 0·0026). T. pallidum was detected by anal canal swab and/or anal lesion swab in 45/196 (23%; 95%CI: 17.3–29.5%) men, 10 with no anal lesion. 74% (69/93) of men with secondary syphilis had T. pallidum detected at any site: 26% (24/93) had detection at ≥2 separate sites. T. pallidum was detected in 6% (12/198) of urine and 12% (6/50) of semen samples. Conclusion Unrecognised oral and anal shedding of T. pallidum may be a factor in sustaining syphilis transmission. Secondary syphilis may be the most infectious stage, with oral transmission possibly being important. Earlier detection and treatment for syphilis to prevent progression to the secondary stage may improve syphilis control.

Background Globally, syphilis remains a major and resurgent public health problem with high incidence rates in many settings, including among men who have sex with men (MSM). Left untreated, syphilis can lead to further transmission, morbidity and enhanced Human Immunodeficiency Virus (HIV) transmission. A primary chancre is classically described as an indurated single painless ulcer at the site of Treponema pallidum inoculation. However, recent clinical experience is that primary syphilis can present atypically, as multiple and/or painful ulcers with features suggestive of genital herpes. We aimed to describe serology and Treponema pallidum polymerase chain reaction (Tp PCR) positive lesions of primary syphilis in men, the rates of painful or multiple lesions, whether there was concurrent genital Herpes simplex virus (HSV) infection and whether concurrent HIV infection altered the presentation. Methods Tp PCR positive results with confirmatory syphilis serology and HSV PCR results reported by VIDRL were identified and compared to MSHC medical records over a five-year period from 2010 to 2014. Results 183 patients fulfilled the criteria of Tp PCR positive primary syphilis. Primary syphilis lesions were frequently painful (49.2%) or multiple (37.7%), and were infrequently associated with HSV (2.7%). Presentation was not significantly altered by HIV status. Anal lesions were more common in HIV positive men (34.2%) than in HIV negative men (11.6%). Syphilis reinfections were more common in HIV positive men (39.5%) than in HIV negative men (11.7%). Conclusion Tp PCR is a useful tool to confirm syphilis as a cause of genital lesions and positivity may precede serological markers. Early syphilis lesions may be clinically misidentified as HSV infection if syphilis is not considered. Awareness of the clinical variability of primary syphilis lesions should be included in health promotion messages to the public and health care providers. Disclosure statement There are no conflicts of interest.

SETTINGVictoria, Australia.OBJECTIVETo describe the epidemiology and control of tuberculosis (TB) in Victoria, 2005-2010.DESIGNRetrospective review of laboratory-confirmed TB in Victoria, 2005-2010. State TB reference laboratory records were matched with Department of Health notification records to obtain laboratory, demographic, clinical and treatment data.RESULTSThe incidence of TB fell in the Australian-born population but increased overall, reflecting an increase in the proportion of overseas-born cases from 88.9% to 95.8% between 2005 and 2010 (P = 0.03). Patients from India and Viet Nam accounted for over one third of all cases. For overseas-born cases, the median time between arrival and diagnosis was 4 years. Half of all diagnoses were pulmonary disease, of which 45.4% were Ziehl-Neelsen smear-positive. Treatment was most commonly self-administered (76.9%), and very few patients defaulted or failed treatment (1.1%). Only 4.1% of cases were linked to another laboratory-confirmed case. Multidrug-resistant TB remained uncommon (1.7% of cases).CONCLUSIONSTB in Victoria remains low by global standards and continues to overwhelmingly affect the overseas-born population. Current TB control strategies in Victoria are effective, but strengthened control in high-burden countries will also improve TB control locally.

SETTING The effectiveness of public health strategies following exposure to multidrug-resistant tuberculosis (MDR-TB) is not clear. OBJECTIVE To perform long-term follow-up of MDR-TB contacts and review individual outcomes and management approaches. DESIGN Retrospective review of MDR-TB contacts identified by the Victorian Department of Health from 1995 to 2010. Health records, including personal medical and pharmacy records and statewide clinical and laboratory TB databases, were searched to identify management strategies and individual outcomes. RESULTS A total of 570 contacts of 47 MDR-TB cases were identified, with a total follow-up period of 3093 person-years of observation (PYO) since exposure. Of 570 contacts, 49 (8.6%) were considered likely to have been infected with Mycobacterium tuberculosis from index cases, and 11/49 (22.5%) of these were prescribed preventive therapy tailored to isolate susceptibility. No MDR-TB cases occurred in those receiving preventive treatment, while two cases were observed in those not treated (incidence 2878/100 000 PYO during the first 2 years post exposure). CONCLUSIONS The risk of MDR-TB transmission to close contacts in this low-prevalence setting highlights the potential for public health strategies involving preventive treatment.

The efficiency for collimated positronium production by charge-exchange in positron collisions with gaseous targets has been investigated in the range 20–396 eV. At 250 and 396 eV, CO2 has been found to be approximately twice as efficient as N2, the previous best neutralising gas at high energies. The efficiency from Xe, whilst lower at low energies, becomes comparable to that from H2 at around 100–120 eV; at ∼250 eV, it is an order of magnitude lower.

Positronium (Ps), a hydrogen-like atom composed of an electron and its antimatter partner, the positron, is formed in considerable quantities whenever positrons interact with matter. It has unexpectedly been found to scatter from a wide variety of atoms and molecules in a way very similar to that of a bare electron moving at the same velocity, despite Ps being neutral and twice the mass.

Cross-sections are presented, both integrated and differential with respect to the longitudinal energy of the ejected positrons, for the fragmentation of Ps in collisions with Xe at 18 and 30eV impact energy and compared with available theory. The shapes of the positron spectra are also compared with those measured in collisions with He at the same impact energy.

Recent progress on the scattering of an ortho-positronium beam is reviewed. Similarities are noted amongst the total cross-sections for positronium scattering from various targets. The integrated Ps fragmentation cross-sections, determined by detecting each of the ejected particles, are presented for collisions with He and Xe atoms. In the case of He, a good agreement is found with theory, whilst preliminary results for Xe suggests that significant target ionisation occurs for this target at 30eV Ps impact energy.

Progress in the production of a monoenergetic Ps beam and in the experimental investigation of its interactions with simple atoms and molecules is reviewed. The current status on measurements of total and positronium fragmentation cross-sections, as well as their comparison with theories, is summarised.

Recent advances in the field of positron-induced ionization and positronium collisions are reviewed. Major outstanding problems are highlighted.

The efficiency for conversion of a positron beam into a positronium (Ps) beam by charge exchange from molecular nitrogen has been investigated in the range of Ps kinetic energy, EPs = 30–250 eV. Measurements have also been made for the production efficiency of collimated Ps from molecular hydrogen in order to make a direct comparison with previous work. The results show that while H2 remains the best converter at lower energies, N2 becomes more efficient from 90 eV upwards. Using N2 as a production gas for collimated Ps, the accessible energy range for Ps scattering is increased by at least 100 eV. A measure of the differential Ps formation cross-section from N2, as well as indirect estimates of Ps–N2 total cross-sections, have also been obtained.

The absolute cross section for the fragmentation of positronium in collision with He atoms has been measured. The results are compared with available theories. The longitudinal energy distributions of positrons resulting from fragmentation have also been determined and are found to display a peak situated just below half the residual energy. This is suggestive of the occurrence of "electron loss to the continuum" in which the two residual charged particles lie in a low relative-velocity Coulomb-continuum state.

Objective. To elucidate the seroepidemiology of hepatitis C in patients with clotting disorders in comparison with other blood borne infections; to examine the effects of hepatitis C on liver function; and to assess the effectiveness of current screening and inactivation procedures used in preventing the transmission of blood borne viruses by clotting factor preparations.Design: A retrospective analysis of the prevalence of antibodies to hepatitis C virus (HCV), hepatitis B virus (HBV) and human immunodeficiency virus (HIV) by means of commercially available enzyme immunoassays (for antibodies to HCV and HIV) or radioimmunoassays (for HBV antibodies and surface antigen). An analysis was made of serum transaminase levels where such information was available and this was correlated with HCV status.Patients and setting: Panels of sera were collected from adults and children with clotting disorders attending two Melbourne haemophilia treatment centres in 1973 (n = 33), 1980 (n = 33), 1984-1985 (n = 111) and 1987-1990 (n = 217) and tested for antibodies to HCV, HBV and HIV.Results: The prevalence of antibodies to HCV in the four panels tested was 45%, 74%, 75% and 76%, and the prevalence of markers of infection with HBV was 66%, 74%, 62% and 65% respectively. No antibodies to HIV were found in sera in Panels I and 11 but the prevalence in Panels III and IV was 23% and 36% respectively. In subjects in whom liver function test results were available, there was a significant association between the presence of antibodies to HCV and raised transaminase levels. Since heat inactivation of clotting factors was commenced in Australia in 1984, no new cases of transmission of HIV by clotting factors has been detected, but transmission of HCV in 19 subjects and HBV in one subject could not be excluded.Conclusions: Hepatitis C infection in haemophiliacs has been a very frequent event, and the presence of antibodies to HCV is associated with an increased incidence of raised transaminase levels. Screening and heat inactivation of clotting factors has prevented further HIV transmission, but exposure to HBV and HCV has not been eliminated.

OBJECTIVE:To determine the relationship between the development of hepatitis C antibody (anti-HCV) and the clinical symptoms in acute hepatitis C.DESIGN:Retrospective analysis of sera from patients with acute non-A non-B hepatitis.SETTING AND PATIENTS:Patients admitted to Fairfield Hospital with the diagnosis of acute non-A non-B hepatitis between 1979 and 1989. Inclusion criteria included a typical clinical illness, accompanied by an alanine aminotransferase level of more than 2.5 times the upper limit of normal (normal, less than or equal to 40 U/L) and negative serological test results for acute hepatitis A and B.MAIN OUTCOME MEASURE:Time to develop anti-HCV after the onset of symptoms in patients with acute hepatitis C.RESULTS:Seroconversion was demonstrated in 26 of the 128 patients who fulfilled the inclusion criteria. In these patients, antibody was detected between one week and 32 weeks after the onset of dark urine; more than half the patients (54%) had seroconverted by four weeks and a third (34%) developed antibodies within two weeks. Of 20 patients who had sera collected within four weeks of the onset of dark urine, 14 (70%) had developed antibody.CONCLUSION:These results suggest that in patients with community-acquired hepatitis C, seroconversion occurs significantly earlier than is observed in patients who have been infected by blood transfusion. Sera taken shortly after the onset of symptomatic hepatitis C may be useful in the diagnosis of this condition.

Parenterally transmitted non-A, non-B (NANB) hepatitis virus or hepatitis C virus is a common cause of both acute and chronic hepatitis. Using a recently developed enzyme-linked immunosorbent assay we looked at the prevalence of antibodies to hepatis C virus (anti-HCV) in a number of groups. People with haemophilia (75.6%) and intravenous drug users (61.9%) had the highest prevalence, while homosexual men attending a sauna (34.1%) and prisoners (30.8%) had a moderately high prevalence of anti-HCV. A lower prevalence of antibody was detected in female prostitutes (10.4%), institutionalised mentally retarded subjects (9.5%), homosexual men requesting human immunodeficiency virus (HIV) testing through their local doctor (8.8%), dialysis patients (5.9%), renal transplant patients (6.9%), and patients referred from a sexually transmitted diseases clinic (6.2%). The lowest prevalence of anti-HCV was recorded in women attending a provincial hospital for antenatal care (0.4%). The predominance of anti-HCV in groups of people exposed to blood-borne and sexually transmitted infections suggests that these routes may be primarily involved in the spread of hepatitis C virus infection.