[Show abstract][Hide abstract] ABSTRACT: To guide control policies, it is important that the determinants of influenza transmission are fully characterized. Such assessment is complex because the risk of influenza infection is multifaceted and depends both on immunity acquired naturally or via vaccination and on the individual level of exposure to influenza in the community or in the household. Here, we analyse a large household cohort study conducted in 2007-2010 in Vietnam using innovative statistical methods to ascertain in an integrative framework the relative contribution of variables that influence the transmission of seasonal (H1N1, H3N2, B) and pandemic H1N1pdm09 influenza. Influenza infection was diagnosed by haemagglutination-inhibition (HI) antibody assay of paired serum samples. We used a Bayesian data augmentation Markov chain Monte Carlo strategy based on digraphs to reconstruct unobserved chains of transmission in households and estimate transmission parameters. The probability of transmission from an infected individual to another household member was 8% (95% CI, 6%, 10%) on average, and varied with pre-season titers, age and household size. Within households of size 3, the probability of transmission from an infected member to a child with low pre-season HI antibody titers was 27% (95% CI 21%-35%). High pre-season HI titers were protective against infection, with a reduction in the hazard of infection of 59% (95% CI, 44%-71%) and 87% (95% CI, 70%-96%) for intermediate (1∶20-1∶40) and high (≥1∶80) HI titers, respectively. Even after correcting for pre-season HI titers, adults had half the infection risk of children. Twenty six percent (95% CI: 21%, 30%) of infections may be attributed to household transmission. Our results highlight the importance of integrated analysis by influenza sub-type, age and pre-season HI titers in order to infer influenza transmission risks in and outside of the household.
[Show abstract][Hide abstract] ABSTRACT: Family plays an important role in the lives of injecting drug users (IDUs) in Vietnam. This study examined the preliminary outcomes of an intervention targeting IDUs and their family members in Vietnam. Eighty-three families, including 83 IDUs and 83 family members, were recruited from 4 communes in Phú Tḥo Province, Vietnam. The 4 communes were randomized to either an intervention condition or a standard care condition. The IDUs and their family members in the intervention condition completed 4 group sessions, with the aims to improve their mental health and family relations and to promote positive behavioral change. The intervention effect was evaluated at baseline and 3- and 6-month follow-up assessments. A significant reduction in depressive symptoms and improvement in family functioning were reported for IDUs in the intervention group compared with those in the standard care group. The family members in the intervention group reported better coping skills at 3 months, fewer depressive symptoms at 6 months, and improved family function at both 3 and 6 months compared with those in the standard care group. However, no significant intervention effect was observed for IDUs in terms of drug-using behavior. This study demonstrates the feasibility and preliminary outcomes of an intervention that simultaneously targets IDUs and their family members in Vietnam. Study findings highlight the importance of including family members and enhancing their role in drug use intervention efforts. (PsycINFO Database Record (c) 2013 APA, all rights reserved).
Psychology of Addictive Behaviors 07/2014; · 2.09 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Introduction of human papillomavirus (HPV) vaccine in national programs has proceeded apace since 2006, mostly in high-income countries. Recently concluded pilots of HPV vaccination in low-income countries have provided important lessons learned for these settings; however, rigorous evaluations of the feasibility of these delivery strategies that effectively reach young adolescents have been few. This paper presents results from a qualitative evaluation of a demonstration program which implemented school-based and health center-based HPV vaccinations to all girls in grade 6, or 11 years of age, for two years in four districts of Vietnam.
BMC Public Health 06/2014; 14(1):556. · 2.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This study investigated whether a large dengue epidemic that struck Hanoi in 2009 also affected a nearby semirural area. Seroconversion (dengue virus-reactive immunoglobulin G enzyme-linked immunosorbent assay) was high during 2009 compared with 2008, but neutralization assays showed that it was caused by both dengue virus and Japanese encephalitis virus infections. The findings highlight the importance of continued Japanese encephalitis virus vaccination and dengue surveillance.
The American journal of tropical medicine and hygiene 03/2014; · 2.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Influenza household transmission studies are required to guide prevention strategies but most passively recruit index cases that seek healthcare. We investigated A(H1N1)pdm09 transmission in a household-based cohort during 2009.
Health-workers visited 270 households weekly, and collected swabs from influenza-like-illness cases. If A(H1N1)pdm09 was RT-PCR-confirmed, all household members had symptoms assessed and swabs collected daily for 10-15 days. Viral RNA was quantified and sequenced and serology performed on pre-pandemic sera.
Index cases were detected in 20 households containing 81 people. 98.5% lacked A(H1N1)pdm09 neutralizing antibodies in pre-pandemic sera. Eleven (18.6%, 95%CI 10.7 - 30.4%) of 59 contacts were infected. Virus genetic diversity within households was negligible and less than between households. Index and secondary cases were distributed between mothers, daughters and sons, and had similar virus-RNA shedding and symptom dynamics. Fathers were rarely infected. Five secondary cases (45%) had no apparent symptoms and three shed virus before symptoms. Secondary infection was associated with index case wet cough (OR 1.56, 95%CI 1.22 - 1.99).
In this cohort of A(H1N1)pdm09 susceptible persons, virus sequencing was capable of discriminating household from community transmission. Household transmission involved mothers and children but rarely fathers. Asymptomatic or pre-symptomatic shedding was common.
The Journal of infection 01/2014; · 4.13 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The interrelationship between the well-being of injecting drug users (IDUs) and their family environment has been widely documented. However, few intervention programs have addressed the needs of both IDUs and their family members.
This study describes a randomized intervention pilot targeting 83 IDUs and 83 of their family members from four communes in Phú Thọ province, Vietnam. The IDUs and family members in the intervention condition received multiple group sessions, with the intent to improve psychological well-being and family relationships. The intervention outcomes (depressive symptoms and family relations) were evaluated at baseline, 3-month and 6-month follow-up assessments.
Depressive symptoms and family relations reported by IDUs were found to be correlated to those reported by their family members. Overall, significant intervention effects on depressive symptoms and family relations were observed for both IDUs and family members. A similar improvement pattern in family relations emerged for both the IDU and family member samples, although the intervention effect of reducing depressive symptoms was more sustainable for family members at the 6-month assessment when compared to the IDU sample.
The intervention pilot addressed challenges faced by IDUs and their family members and revealed correlated outcomes for the two groups. Findings suggest a vital need to include family members in future drug prevention and harm reduction intervention efforts.
Drug and alcohol dependence 01/2014; 134:348-354. · 3.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Understanding global influenza migration and persistence is crucial for vaccine strain selection. Using 240 new human influenza A virus whole genomes collected in Vietnam during 2001-2008, we looked for persistence patterns and migratory connections between Vietnam and other countries. We found that viruses in Vietnam migrate to and from China, Hong Kong, Taiwan, Cambodia, Japan, South Korea, and the United States. We attempted to reduce geographic bias by generating phylogenies subsampled at the year and country levels. However, migration events in these phylogenies were still driven by the presence or absence of sequence data, indicating that an epidemiologic study design that controls for prevalence is required for robust migration analysis. With whole-genome data, most migration events are not detectable from the phylogeny of the hemagglutinin segment alone, although general migratory relationships between Vietnam and other countries are visible in the hemagglutinin phylogeny. It is possible that virus lineages in Vietnam persisted for >1 year.
[Show abstract][Hide abstract] ABSTRACT: There are no contemporary data available describing human immunity to novel influenza A/H7N9. Using 1723 prospectively collected serum samples in southern Vietnam, we tested for antibodies to five avian influenza antigens using a protein microarray. General-population antibody titers against subtype H7 virus are higher than antibody titers against subtype H5, and lower than titers against H9. The highest titers were observed for human influenza subtypes. Titers to avian influenza antigens increased with age and with geometric mean antibody titer to human influenza antigens. There were no titer differences between the urban and the rural location in our study.
The Journal of Infectious Diseases 05/2013; · 5.85 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The emergence of New Delhi metallo-beta-lactamase 1 resistant to the powerfull antibiotic carbapenem in Gram-negative bacteria constitutes an important growing public health threat. After discovered in 2008 in Sweden from Indian patient previously hospitalized in New Delhi-India and now worldwide. The NDM -1 bacteria are now not only reported in hospital settings but also in community. The conresponding gene is mostly plasmid-located, further enhancing their spread. This review were summarized the current knowledge on NDM -1 Gram negative bacteria, including distribution, epidemiology, clinical and molercular characterization, method to detect NDM -1 bacteria as well as the problems of NDM -1 need to be addressed.
Preventive Medicine 01/2013; 6(142):20-30. · 3.50 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Serological studies are the gold standard method to estimate influenza infection attack rates (ARs) in human populations. In a common protocol, blood samples are collected before and after the epidemic in a cohort of individuals; and a rise in haemagglutination-inhibition (HI) antibody titers during the epidemic is considered as a marker of infection. Because of inherent measurement errors, a 2-fold rise is usually considered as insufficient evidence for infection and seroconversion is therefore typically defined as a 4-fold rise or more. Here, we revisit this widely accepted 70-year old criterion. We develop a Markov chain Monte Carlo data augmentation model to quantify measurement errors and reconstruct the distribution of latent true serological status in a Vietnamese 3-year serological cohort, in which replicate measurements were available. We estimate that the 1-sided probability of a 2-fold error is 9.3% (95% Credible Interval, CI: 3.3%, 17.6%) when antibody titer is below 10 but is 20.2% (95% CI: 15.9%, 24.0%) otherwise. After correction for measurement errors, we find that the proportion of individuals with 2-fold rises in antibody titers was too large to be explained by measurement errors alone. Estimates of ARs vary greatly depending on whether those individuals are included in the definition of the infected population. A simulation study shows that our method is unbiased. The 4-fold rise case definition is relevant when aiming at a specific diagnostic for individual cases, but the justification is less obvious when the objective is to estimate ARs. In particular, it may lead to large underestimates of ARs. Determining which biological phenomenon contributes most to 2-fold rises in antibody titers is essential to assess bias with the traditional case definition and offer improved estimates of influenza ARs.
[Show abstract][Hide abstract] ABSTRACT: Since the end of the 1990s, unexplained outbreaks of acute encephalitis in children coinciding with litchi harvesting (May-July) have been documented in the Bac Giang Province in northern Vietnam. A retrospective ecologic analysis of data for 2004-2009 involving environmental, agronomic, and climatic factors was conducted to investigate the suspected association between the outbreaks and litchi harvesting. The clinical, biological, and immunologic characteristics of the patients suggested a viral etiology. The ecologic study revealed an independent association between litchi plantation surface proportion and acute encephalitis incidence: Incidence rate ratios were 1.52 (95% CI 0.90-2.57), 2.94 (95% CI 1.88-4.60), and 2.76 (95% CI 1.76-4.32) for second, third, and fourth quartiles, respectively, compared with the lowest quartile. This ecologic study confirmed the suspected association between incidence of acute encephalitis and litchi plantations and should be followed by other studies to identify the causative agent for this syndrome.
[Show abstract][Hide abstract] ABSTRACT: Emergence of Gram-negative pathogens carrying the New Delhi metallo-beta-lactamase gene (NDM-1) conveying carbapenem resistance is an urgent and global concern.…
Journal of clinical microbiology 10/2012; · 4.16 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The GAVI Alliance's decision in late 2011 to invite developing countries to apply for funding for human papillomavirus (HPV) vaccine introduction underscores the importance of understanding levels of HPV vaccine acceptance in developing country settings. In this paper, we present findings from qualitative research on parents' rationales for vaccinating or not vaccinating their daughters (vaccine acceptance) and their decision-making process in the context of an HPV vaccination demonstration project in Vietnam (2008-2009).
We designed a descriptive qualitative study of HPV vaccine acceptability among parents of girls eligible for vaccination in four districts of two provinces in Vietnama. The study was implemented after each of two years of vaccinations was completed. In total, 133 parents participated in 16 focus group discussions and 27 semi-structured interviews.
Focus group discussions and in-depth interviews with parents of girls vaccinated revealed that they were generally very supportive of immunization for disease prevention and of vaccinating girls against HPV. The involvement of the National Expanded Program of Immunization in the demonstration project lent credibility to the HPV vaccine, contributing to high levels of acceptance. For parents who declined participation, concerns about side effects, the possibility that the vaccine was experimental, and the possible impact of the vaccine on future fertility rose to the surface. In terms of the decision-making process, many parents exhibited 'active decision-making,' reaching out to friends, family, and opinion leaders for guidance prior to making their decision.
Vietnam's HPV vaccination experience speaks to the importance of close collaboration with the government to make the most of high levels of trust, and to reduce suspicions about new vaccines that may arise in the context of vaccine introduction in developing country settings.
BMC Public Health 08/2012; 12:629. · 2.08 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background: Pregnant women fear being identified as HIV-1-infected and this has hampered prevention programmes and the calculation of transmission rates in Viet Nam. We introduced post-test counselling, antiretroviral prophylaxis, and formula feeding, and determined the vertical transmission rate in parts of Northern Viet Nam. Methods: HIV infection was identified in 234 pregnant women; 182 (77.8%) accepted follow-up of their children. Counselling was given on 3-7 occasions for altogether approximately 6 h on antiretroviral prophylaxis and formula feeding to avoid transmission, and on the importance of surveillance of the child. All children were formula-fed. A polymerase chain reaction (PCR) was used for the diagnosis of HIV-1 in the children. One hundred and thirty-five of the 182 mothers allowed ≥3 blood samples to be taken from birth to ≥1 y of age, 32/182 provided a birth sample only, and 15/182 provided a sample later only. Nevirapine was given at delivery to 93/135 (69%) women, and to 128/135 (95%) children. Additionally, combination therapy was given to 15/135 (11%) who entered the study before delivery, and azidothymidine to their children for 1 week. Results: Nine of 135 (6.7%) children became infected and 2/15 of the others, giving altogether 11/150 infected (7.3%). Intrauterine transmission was identified in 7/167 (4.2%) children by a positive PCR test at birth. PCR was negative at birth but positive at 1 month in 2/135 (1.5%), pointing to delivery-associated transmission. Thus, intrauterine transmission accounted for 78% (7/9). None of the uninfected children died, but 3/11 (p =0.004) of the HIV-1-infected died (in AIDS). Conclusion: Post-test confidential counselling, formula feeding, and antiretroviral prophylaxis resulted in low rates of delivery-associated and late HIV-1 transmissions.
[Show abstract][Hide abstract] ABSTRACT: 18,500 laboratory-confirmed deaths caused by the 2009 pandemic influenza A H1N1 were reported worldwide for the period April, 2009, to August, 2010. This number is likely to be only a fraction of the true number of the deaths associated with 2009 pandemic influenza A H1N1. We aimed to estimate the global number of deaths during the first 12 months of virus circulation in each country.
We calculated crude respiratory mortality rates associated with the 2009 pandemic influenza A H1N1 strain by age (0-17 years, 18-64 years, and >64 years) using the cumulative (12 months) virus-associated symptomatic attack rates from 12 countries and symptomatic case fatality ratios (sCFR) from five high-income countries. To adjust crude mortality rates for differences between countries in risk of death from influenza, we developed a respiratory mortality multiplier equal to the ratio of the median lower respiratory tract infection mortality rate in each WHO region mortality stratum to the median in countries with very low mortality. We calculated cardiovascular disease mortality rates associated with 2009 pandemic influenza A H1N1 infection with the ratio of excess deaths from cardiovascular and respiratory diseases during the pandemic in five countries and multiplied these values by the crude respiratory disease mortality rate associated with the virus. Respiratory and cardiovascular mortality rates associated with 2009 pandemic influenza A H1N1 were multiplied by age to calculate the number of associated deaths.
We estimate that globally there were 201,200 respiratory deaths (range 105,700-395,600) with an additional 83,300 cardiovascular deaths (46,000-179,900) associated with 2009 pandemic influenza A H1N1. 80% of the respiratory and cardiovascular deaths were in people younger than 65 years and 51% occurred in southeast Asia and Africa.
Our estimate of respiratory and cardiovascular mortality associated with the 2009 pandemic influenza A H1N1 was 15 times higher than reported laboratory-confirmed deaths. Although no estimates of sCFRs were available from Africa and southeast Asia, a disproportionate number of estimated pandemic deaths might have occurred in these regions. Therefore, efforts to prevent influenza need to effectively target these regions in future pandemics.
The Lancet Infectious Diseases 06/2012; 12(9):687-95. · 19.97 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: During 2007-2008, surveillance of transmitted human immunodeficiency virus (HIV) drug resistance (TDR) was performed following World Health Organization guidance among clients with newly diagnosed HIV infection attending voluntary counseling and testing (VCT) sites in Ho Chi Minh City (HCMC), Vietnam. Moderate (5%-15%) TDR to nonnucleoside reverse-transcriptase inhibitors (NNRTIs) was observed among VCT clients aged 18-21 years. Follow-up surveillance of TDR in HCMC and other geographic regions of Vietnam is warranted. Data generated will guide the national HIV drug resistance surveillance strategy and support selection of current and future first-line antiretroviral therapy and HIV prevention programs.
[Show abstract][Hide abstract] ABSTRACT: Prospective community-based studies have provided fundamental insights into the epidemiology of influenza in temperate regions, but few comparable studies have been undertaken in the tropics. The authors conducted prospective influenza surveillance and intermittent seroprevalence surveys in a household-based cohort in Vietnam between December 2007 and April 2010, resulting in 1,793 person-seasons of influenza surveillance. Age- and sex-standardized estimates of the risk of acquiring any influenza infection per season in persons 5 years of age or older were 21.1% (95% confidence interval: 17.4, 24.7) in season 1, 26.4% (95% confidence interval: 22.6, 30.2) in season 2, and 17.0% (95% confidence interval: 13.6, 20.4) in season 3. Some individuals experienced multiple episodes of infection with different influenza types/subtypes in the same season (n = 27) or reinfection with the same subtype in different seasons (n = 22). The highest risk of influenza infection was in persons 5-9 years old, in whom the risk of influenza infection per season was 41.8%. Although the highest infection risk was in school-aged children, there were important heterogeneities in the age of infection by subtype and season. These heterogeneities could influence the impact of school closure and childhood vaccination on influenza transmission in tropical areas, such as Vietnam.
American journal of epidemiology 03/2012; 175(10):1062-74. · 5.59 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: In Vietnam there has been relatively little success in controlling the HIV epidemic, in part because the subpopulations most exposed to the virus are often difficult to engage in prevention research and programs. In this qualitative study we explored social contexts shaping HIV risk behaviors among Vietnamese men involved in unskilled, unregistered, and low-income labor in urban settings. Based on self-disclosed behaviors, it is clear that these men were at high risk of sexually transmitted infection (STI). Evidence emerged from the interview data highlighting equivalent influences of individual psychological factors, social integration, social barriers, and accessibility regarding drug use and sexual risk behavior. Psychological influences such as tedium, distress, fatalism and revenge, and the strong effects of collective decision making and fear of social isolation appeared important for these men living on the economic and social
margins of this rapidly urbanizing society. The study findings suggest directions for research and culturally appropriate HIV preventive education and services for these men.
Qualitative Health Research 01/2012; 22(2):871-879. · 2.19 Impact Factor