Can antiviral drugs contain pandemic influenza transmission?

Antiviral drugs dispensed during the 2009 influenza pandemic generally failed to contain transmission. This poses the question of whether preparedness for a future pandemic should include plans to use antiviral drugs to mitigate transmission.Simulations using a standard transmission model that allows for infected arrivals and delayed vaccination show that attempts to contain transmission require relatively few antiviral doses.

A simple, valid, numerical score for grading chest x-ray severity in adult smear-positive pulmonary tuberculosis.

Background: The grading of radiological severity in clinical trials in tuberculosis (TB) remains unstandardised. The aim of this study was to generate and validate a numerical score for grading chest x-ray (CXR) severity and predicting response to treatment in adults with smear-positive pulmonary TB.

Methods: At a TB clinic in Papua, Indonesia, serial CXRs were performed at diagnosis, 2 and 6 months in 115 adults with smear-positive pulmonary TB.

Studies needed to address public health challenges of the 2009 H1N1 influenza pandemic: insights from modeling.

In light of the 2009 influenza pandemic and potential future pandemics, Maria Van Kerkhove and colleagues anticipate six public health challenges and the data needed to support sound public health decision making.

Estimating antiviral effectiveness against pandemic influenza using household data.

Current estimates of antiviral effectiveness for influenza are based on the existing strains of the virus. Should a pandemic strain emerge, strain-specific estimates will be required as early as possible to ensure that antiviral stockpiles are used optimally and to compare the benefits of using antivirals as prophylaxis or to treat cases. We present a method to measure antiviral effectiveness using early pandemic data on household outbreak sizes, including households that are provided with antivirals for prophylaxis and those provided with antivirals for treatment only.

Age-specific risk factors for sporadic Campylobacter infection in regional Australia.

In a case-control study in the Hunter region of New South Wales, Australia, 354 cases and 593 controls were recruited to investigate meat, other food, and environmental exposures as potential risk factors for domestically acquired Campylobacter illness. In a multivariable model, illness was significantly associated with household exposure to diarrheal illness, consumption of restaurant chicken or beef, eating two or more "fast" food meals in a week, and overseas travel. Comparing exposures for the 0- to 4-year and 5-year and older age groups allowed detection of additional risk factors.

Spatial dynamics of an epidemic of severe acute respiratory syndrome in an urban area.

Objective: To map risk of exposure to severe acute respiratory syndrome (SARS) in an urban area and assess the ability of traditional interventions to control dispersion of the disease.

Methods: Data on the Beijing SARS epidemic were used to map spatial clusters of identified contacts and to estimate transmission of SARS using a model with a time-dependent transmission rate.

Results: The estimated transmission rate decreased dramatically from 20 to 30 April 2003.

The waiting time for inter-country spread of pandemic influenza.

Background: The time delay between the start of an influenza pandemic and its subsequent initiation in other countries is highly relevant to preparedness planning. We quantify the distribution of this random time in terms of the separate components of this delay, and assess how the delay may be extended by non-pharmaceutical interventions.

Methods And Findings: The model constructed for this time delay accounts for: (i) epidemic growth in the source region, (ii) the delay until an infected individual from the source region seeks to travel to an at-risk country, (iii) the chance that infected travelers are detected by screening at exit and entry borders, (iv) the possibility of in-flight transmission, (v) the chance that an infected arrival might not initiate an epidemic, and (vi) the delay until infection in the at-risk country gathers momentum.

Population-based detection of systolic and diastolic dysfunction with amino-terminal pro-B-type natriuretic peptide.

Background: There is limited information regarding the clinical utility of amino-terminal pro-B-type natriuretic peptide (NT-proBNP) for the detection of left ventricular (LV) dysfunction in the community. We evaluated predictors of circulating NT-proBNP levels and determined the utility of NT-proBNP to detect systolic and diastolic LV dysfunction in older adults.

Methods: A population-based sample of 1229 older adults (mean age 69.

An analysis for a cross-over cohort study with an application to the study of triggers of Menière's disease.

When studying the effect of a transient exposure on the risk of a rare illness, for time and cost effectiveness it is desirable to follow a cohort of individuals who are 'prone' to the illness over an observation period. In this paper, we present a method of analysis for data arising from such a study. The proposed method can be used to estimate the relative risk of an exposure triggering the illness and the distribution of the time delay from exposure to the onset of illness.

Low-level fluoroquinolone resistance among Campylobacter jejuni isolates in Australia.

Background: Ciprofloxacin-resistant Campylobacter jejuni isolates obtained from infected patients in Australia have not been detected in studies of isolates from specific geographic areas. The Australian government has prohibited the use of fluoroquinolone in food-producing animals. To assess the impact of this policy, we have examined the antimicrobial susceptibility of isolates from 5 Australian states.

Air travel and the risk of deep vein thrombosis.

Background: The magnitude of the risk of venous thromboembolism (VTE) following air travel has been difficult to resolve due to a lack of adequate data. We determine the association more precisely by using a large dataset and an improved method of analysis.

Method: Data on air-travel history for each of 5,196 patients hospitalised for VTE in Western Australia from 1981 to 1999 is analysed using a log-linear regression model for the probability that a flight triggers VTE and for the baseline hazard rate for VTE hospitalisation.

Control of transmission with two types of infection.

The effectiveness of a vaccination strategy to control transmission of an infectious disease depends on the way vaccine doses are distributed to individuals in a community of households. Here we show that this dependence is more complicated when acquisition and severity of illness are determined by the size of the infecting dose, as is thought to be the case for measles and varicella. Two alternative formulations for the way vaccination changes an individual's susceptibility and infectivity show that vaccination coverage, the nature of the vaccine response and the distribution of household size also have a big impact on which strategy is more effective.

Prevalence of heart failure and systolic ventricular dysfunction in older Australians: the Canberra Heart Study.

Objective: To estimate the prevalence of heart failure (HF) and left ventricular (LV) systolic dysfunction in a population-based sample of older Australians.

Design, Setting And Participants: A cross-sectional survey of 2000 randomly selected residents of Canberra, aged 60-86 years, conducted between February 2002 and June 2003. Participants were assessed by history, physical examination by a cardiologist, and echocardiography.

Estimating vaccine effects from studies of outbreaks in household pairs.

The traditional way to measure efficacy of a vaccine, with respect to reduced susceptibility and reduced infectivity once infected, is to look at relative attack rates. Although straightforward to apply, such measures do not take disease transmission into account, with the consequence that they can depend strongly on the community setting, the duration of the study period, the way participants are recruited into the study and the virulence of the infection. Sometimes they give a very misleading assessment of the vaccine, as we illustrate by examples.

Analysis of a potential trigger of an acute illness.

Sometimes certain short-term risk exposures are postulated to act as a trigger for the onset of a specific acute illness. When the incidence of the illness is low it is desirable to investigate this possible association using only data on cases detected during a specific observation period. Here we propose an analysis for such a study based on a model expressed in terms of the probability that the exposure triggers the illness and a random delay from a triggered illness until its diagnosis.

Monitoring measles elimination in Victoria.

Objectives: To weigh the evidence from outbreak data that Victoria has achieved, and is maintaining, elimination of measles. To identify age groups that measles vaccination has not protected adequately.

Methods: Data on observed measles outbreaks in Victoria since the start of 1998 are used to estimate the reproduction number of cases, and the probability that it is maintained below unity, its threshold value for elimination.

Controlling emerging infectious diseases like SARS.

To control emerging infectious diseases like SARS, it is necessary to resort to basic control measures that limit exposures to infectious individuals. These measures include isolating cases at diagnosis, quarantining household members and tracing contacts of diagnosed cases, providing the community with advice on how to reduce exposures, and closing schools. To justify such intervention it is important to understand how well each of these measures helps to limit transmission.

The effect of transient exposures on the risk of an acute illness with low hazard rate.

There are many situations where intermittent short-term exposures of a certain kind are thought to temporarily enhance the risk of onset of an adverse health event (illness). When the hazard rate of the illness is small it is desirable to investigate this possible association using only data on cases occurring in a finite observation period. Here we extend a method for such an analysis by allowing the baseline hazard for the illness to depend on the increasing age over the observation period and using age at the times of exposure, a time dependent variable, as a covariate in the effect of the transient exposure.

Does ambient temperature affect foodborne disease?

Background: Foodborne illness is a significant public health issue in most countries, including Australia. We examined the association between temperature and salmonellosis notifications, and compared these associations for 5 Australian cities.

Methods: Log-linear models describing monthly salmonellosis notifications in terms of calendar time and monthly average temperatures were fitted over the period 1991 to 2001 for each city.

Estimating vaccine effects on transmission of infection from household outbreak data.

This article is concerned with a method for making inferences about various measures of vaccine efficacy. These measures describe reductions in susceptibility and in the potential to transmit infection. The method uses data on household outbreaks; it is based on a model that allows for transmission of infection both from within a household and from the outside.

Age-specific back-projection of HIV diagnosis data.

A method for reconstructing the HIV infection curve from data on both HIV and AIDS diagnoses is enhanced by using age as a covariate and by using the diagnosis data to estimate parameters that were previously assumed known. Maximum likelihood estimation is used for parameters of the induction distribution. Each of the set of parameters that specify the baseline rate of infection over time and the set of parameters giving the relative susceptibility over age are estimated by maximizing the likelihood subject to a smoothness requirement.