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Alexandra M Oster - Top 30 Publications

HIV Transmission Dynamics among Foreign-born Persons in the United States.

In the United States (U.S.), foreign-born persons are disproportionately affected by HIV and differ epidemiologically from U.S.-born persons with diagnosed HIV infection. Understanding HIV transmission dynamics among foreign-born persons is important to guide HIV prevention efforts for these populations. We conducted molecular transmission network analysis to describe HIV transmission dynamics among foreign-born persons with diagnosed HIV.

Receipt and timing of HIV drug resistance testing in six U.S. jurisdictions.

The Department of Health and Human Services recommends drug resistance testing at linkage to HIV care. Because receipt and timing of testing are not well characterized, we examined testing patterns among persons with diagnosed HIV who are linked to care. Using surveillance data in six jurisdictions for persons aged ≥13 years with HIV infection diagnosed in 2013, we assessed the proportion receiving testing, and among these, the proportion receiving testing at linkage. Multivariable log-binomial regression modeling estimated associations between selected characteristics and receipt of testing (1) overall, and (2) at linkage among those tested. Of 9,408 persons linked to care, 66% received resistance testing, among whom 68% received testing at linkage. Less testing was observed among male persons who inject drugs (PWID), compared with men who have sex with men (adjusted prevalence ratio [aPR]: 0.88; 95% confidence interval [CI]: 0.81-0.97) and persons living in areas with population <500,000 compared with those in areas with population ≥2,500,000 (aPR: 0.88; CI: 0.84-0.93). In certain jurisdictions, testing was lower for persons with initial CD4 counts ≥500 cells/mm(3), compared with those with CD4 counts <200 cells/mm(3) (aPR range: 0.80-0.85). Of those tested, testing at linkage was lower among male PWID (aPR: 0.85; CI: 0.75-0.95) and, in some jurisdictions, persons with CD4 counts ≥500 cells/mm(3) (aPR range: 0.63-0.73). Two-thirds of persons with diagnosed HIV who were linked to care received resistance testing, and most received testing at linkage as recommended. Improving receipt and timing of testing among male PWID, persons in less populous settings, and in all jurisdictions, regardless of CD4 count, may improve care outcomes.

Transmission fitness of drug-resistant HIV revealed in a surveillance system transmission network.

Test-and-treat programs are central to the global control of HIV, but transmitted drug resistance threatens the effectiveness of these programs. HIV mutations conferring resistance to antiretroviral drugs reduce replicative fitness in vitro, but their effect on propagation in vivo is less understood. Here, we estimate transmission fitness of these mutations in antiretroviral-naïve populations in the U.S. National HIV Surveillance System by comparing their frequency of clustering in a genetic transmission network relative with wild-type viruses. The large dataset (66,221 persons), comprising 30,196 antiretroviral-naïve persons, permitted the evaluation of sixty-nine resistance mutations. Decreased transmission fitness was demonstrated for twenty-three mutations, including M184V. In contrast, many high prevalence mutations (e.g. K103N, Y181C, and L90M) had transmission fitness that was indistinguishable from or exceeded wild-type fitness, permitting the establishment of large, self-sustaining drug resistance reservoirs. We highlight implications of these findings on strategies to preserve global treatment effectiveness.

HIV acquisition and transmission among men who have sex with men and women: What we know and how to prevent it.

Men who have sex with men and women (MSMW) compose a subset of men who have sex with men (MSM) and represent an estimated 35% of MSM. Research on the HIV risk behaviors of MSMW has largely focused on their behaviors in comparison to men who have sex with men only (MSMO). Results suggest that compared to MSMO, MSMW are less likely to have ever had an HIV test, are at greater risk of being unaware of their HIV infection and are less likely to have encountered HIV prevention activities or materials. Additional research is needed to provide a more comprehensive understanding of the unique sexual behaviors and lived experience of MSMW as a group in order to better inform HIV prevention efforts. The purpose of this paper is to summarize existing data and discuss strategies to reduce HIV acquisition and transmission among MSMW.

Increasing HIV-1 subtype diversity in seven states, United States, 2006-2013.

The aim of the analysis was to explore HIV-1 subtype diversity in the United States and understand differences in prevalence of non-B subtypes and circulating recombinant forms (CRFs) between demographic/risk groups and over time.

HIV-1 Infection and Transmission Networks of Younger People in Chicago, Illinois, 2005-2011.

Analysis of HIV nucleotide sequences can be used to identify people with highly similar HIV strains and understand transmission patterns. The objective of this study was to identify groups of people highly connected by HIV transmission and the extent to which transmission occurred within and between geographic areas in Chicago, Illinois.

Male-to-Female Sexual Transmission of Zika Virus-United States, January-April 2016.

We report on 9 cases of male-to-female sexual transmission of Zika virus in the United States occurring January-April 2016. This report summarizes new information about both timing of exposure and symptoms of sexually transmitted Zika virus disease, and results of semen testing for Zika virus from 2 male travelers.

HIV Testing Experience Before HIV Diagnosis Among Men Who Have Sex with Men - 21 Jurisdictions, United States, 2007-2013.

Gay, bisexual, and other men who have sex with men (MSM) continue to be the population most affected by human immunodeficiency virus (HIV) in the United States. In 2014, 81% of diagnoses of HIV infection were among adult and adolescent males, and among these, 83% of infections were attributable to male-to-male sexual contact (1). Since 2006, CDC has recommended HIV testing at least annually for sexually active MSM to foster early detection of HIV infection and prevent HIV transmission (2,3). Several initiatives and strategies during the past decade have aimed to expand HIV testing among MSM to increase early diagnosis and treatment and reduce transmission. To better understand HIV testing patterns among MSM with diagnosed HIV infection, CDC analyzed data for 2007-2013 from jurisdictions conducting HIV incidence surveillance as part of CDC's National HIV Surveillance System (NHSS). Findings from this analysis suggest that increasing percentages of MSM have had a negative HIV test during the 12 months before diagnosis (48% in 2007, 56% in 2013, among those with a known date of previous negative HIV test), indicating a trend toward increased HIV testing and earlier HIV diagnosis among persons most at risk for HIV.

Early Identification and Prevention of the Spread of Ebola - United States.

In response to the 2014-2016 Ebola virus disease (Ebola) epidemic in West Africa, CDC prepared for the potential introduction of Ebola into the United States. The immediate goals were to rapidly identify and isolate any cases of Ebola, prevent transmission, and promote timely treatment of affected patients. CDC's technical expertise and the collaboration of multiple partners in state, local, and municipal public health departments; health care facilities; emergency medical services; and U.S. government agencies were essential to the domestic preparedness and response to the Ebola epidemic and relied on longstanding partnerships. CDC established a comprehensive response that included two new strategies: 1) active monitoring of travelers arriving from countries affected by Ebola and other persons at risk for Ebola and 2) a tiered system of hospital facility preparedness that enabled prioritization of training. CDC rapidly deployed a diagnostic assay for Ebola virus (EBOV) to public health laboratories. Guidance was developed to assist in evaluation of patients possibly infected with EBOV, for appropriate infection control, to support emergency responders, and for handling of infectious waste. CDC rapid response teams were formed to provide assistance within 24 hours to a health care facility managing a patient with Ebola. As a result of the collaborations to rapidly identify, isolate, and manage Ebola patients and the extensive preparations to prevent spread of EBOV, the United States is now better prepared to address the next global infectious disease threat.The activities summarized in this report would not have been possible without collaboration with many U.S. and international partners (

The International Dimension of the U.S. HIV Transmission Network and Onward Transmission of HIV Recently Imported into the United States.

The majority of HIV infections in the United States can be traced back to a single introduction in late 1960s or early 1970s. However, it remains unclear whether subsequent introductions of HIV into the United States have given rise to onward transmission. Genetic transmission networks can aid in understanding HIV transmission. We constructed a genetic distance-based transmission network using HIV-1 pol sequences reported to the U.S. National HIV Surveillance System (n = 41,539) and all publicly available non-U.S. HIV-1 pol sequences (n = 86,215). Of the 13,145 U.S. persons clustered in the network, 457 (3.5%) were genetically linked to a potential transmission partner outside the United States. For internationally connected persons residing in but born outside the United States, 61% had a connection to their country of birth or to another country that shared a language with their country of birth. Bayesian molecular clock phylogenetic analyses indicate that introduced nonsubtype B infections have resulted in onward transmission within the United States.

Update: Interim Guidance for Prevention of Sexual Transmission of Zika Virus--United States, 2016.

CDC issued interim guidance for the prevention of sexual transmission of Zika virus on February 5, 2016. The following recommendations apply to men who have traveled to or reside in areas with active Zika virus transmission and their female or male sex partners. These recommendations replace the previously issued recommendations and are updated to include time intervals after travel to areas with active Zika virus transmission or after Zika virus infection for taking precautions to reduce the risk for sexual transmission. This guidance defines potential sexual exposure to Zika virus as any person who has had sex (i.e., vaginal intercourse, anal intercourse, or fellatio) without a condom with a man who has traveled to or resides in an area with active Zika virus transmission. This guidance will be updated as more information becomes available.

Update: Interim Guidance for Health Care Providers Caring for Women of Reproductive Age with Possible Zika Virus Exposure--United States, 2016.

CDC has updated its interim guidance for U.S. health care providers caring for women of reproductive age with possible Zika virus exposure to include recommendations on counseling women and men with possible Zika virus exposure who are interested in conceiving. This guidance is based on limited available data on persistence of Zika virus RNA in blood and semen. Women who have Zika virus disease should wait at least 8 weeks after symptom onset to attempt conception, and men with Zika virus disease should wait at least 6 months after symptom onset to attempt conception. Women and men with possible exposure to Zika virus but without clinical illness consistent with Zika virus disease should wait at least 8 weeks after exposure to attempt conception. Possible exposure to Zika virus is defined as travel to or residence in an area of active Zika virus transmission (, or sex (vaginal intercourse, anal intercourse, or fellatio) without a condom with a man who traveled to or resided in an area of active transmission. Women and men who reside in areas of active Zika virus transmission should talk with their health care provider about attempting conception. This guidance also provides updated recommendations on testing of pregnant women with possible Zika virus exposure. These recommendations will be updated when additional data become available.

Transmission of Zika Virus Through Sexual Contact with Travelers to Areas of Ongoing Transmission - Continental United States, 2016.

Zika virus is a flavivirus closely related to dengue, West Nile, and yellow fever viruses. Although spread is primarily by Aedes species mosquitoes, two instances of sexual transmission of Zika virus have been reported, and replicative virus has been isolated from semen of one man with hematospermia. On February 5, 2016, CDC published recommendations for preventing sexual transmission of Zika virus. Updated prevention guidelines were published on February 23. During February 6-22, 2016, CDC received reports of 14 instances of suspected sexual transmission of Zika virus. Among these, two laboratory-confirmed cases and four probable cases of Zika virus disease have been identified among women whose only known risk factor was sexual contact with a symptomatic male partner with recent travel to an area with ongoing Zika virus transmission. Two instances have been excluded based on additional information, and six others are still under investigation. State, territorial, and local public health departments, clinicians, and the public should be aware of current recommendations for preventing sexual transmission of Zika virus, particularly to pregnant women. Men who reside in or have traveled to an area of ongoing Zika virus transmission and have a pregnant partner should abstain from sexual activity or consistently and correctly use condoms during sex with their pregnant partner for the duration of the pregnancy.

Interim Guidelines for Prevention of Sexual Transmission of Zika Virus - United States, 2016.

Zika virus is a mosquito-borne flavivirus primarily transmitted by Aedes aegypti mosquitoes (1,2). Infection with Zika virus is asymptomatic in an estimated 80% of cases (2,3), and when Zika virus does cause illness, symptoms are generally mild and self-limited. Recent evidence suggests a possible association between maternal Zika virus infection and adverse fetal outcomes, such as congenital microcephaly (4,5), as well as a possible association with Guillain-Barré syndrome. Currently, no vaccine or medication exists to prevent or treat Zika virus infection. Persons residing in or traveling to areas of active Zika virus transmission should take steps to prevent Zika virus infection through prevention of mosquito bites (

Disparities in Consistent Retention in HIV Care--11 States and the District of Columbia, 2011-2013.

In 2013, 45% of new human immunodeficiency virus (HIV) infection diagnoses occurred in non-Hispanic blacks/African Americans (blacks) (1), who represent 12% of the U.S.

The evolving contribution of emergency department testing studies: from risk to care.

Molecular analysis allows inference into HIV transmission among young men who have sex with men in the United States.

The objective of this study is to understand the spread of HIV among and between age and racial/ethnic groups of men who engage in male-to-male sexual contact (MSM) in the United States.

Clinical Inquiries Received by CDC Regarding Suspected Ebola Virus Disease in Children--United States, July 9, 2014-January 4, 2015.

The 2014–2015 Ebola virus disease (Ebola) epidemic is the largest in history and represents the first time Ebola has been diagnosed in the United States. On July 9, 2014, CDC activated its Emergency Operations Center and established an Ebola clinical consultation service to assist U.S. state and local public health officials and health care providers with the evaluation of suspected cases. CDC reviewed all 89 inquiries received by the consultation service during July 9, 2014– January 4, 2015, about children (persons aged ≤18 years). Most (56 [63%]) children had no identifiable epidemiologic risk factors for Ebola; among the 33 (37%) who did have an epidemiologic risk factor, in every case this was travel from an Ebola-affected country. Thirty-two of these children met criteria for a person under investigation (PUI) because of clinical signs or symptoms. Fifteen PUIs had blood samples tested for Ebola virus RNA by reverse transcription–polymerase chain reaction; all tested negative. Febrile children who have recently traveled from an Ebola-affected country can be expected to have other common diagnoses, such as malaria and influenza, and in the absence of epidemiologic risk factors for Ebola, the likelihood of Ebola is extremely low. Delaying evaluation and treatment for these other more common illnesses might lead to poorer clinical outcomes. Additionally, many health care providers expressed concerns about whether and how parents should be allowed in the isolation room. While maintaining an appropriate level of vigilance for Ebola, public health officials and health care providers should ensure that pediatric PUIs receive timely triage, diagnosis, and treatment of other more common illnesses, and care reflecting best practices in supporting children’s psychosocial needs.

Using Molecular HIV Surveillance Data to Understand Transmission Between Subpopulations in the United States.

Studying HIV transmission networks provides insight into the spread of HIV and opportunities for intervention. We identified transmission dynamics among risk groups and racial/ethnic groups in the United States.

Unhealthy environments, unhealthy consequences: Experienced homonegativity and HIV infection risk among young men who have sex with men.

Unfavourable social environments can negatively affect the health of gay, bisexual, and other men who have sex with men (MSM). We described how experienced homonegativity - negative perceptions and treatment that MSM encounter due to their sexual orientations - can increase HIV vulnerability among young MSM. Participants (n = 44) were young MSM diagnosed with HIV infection during January 2006-June 2009. All participants completed questionnaires that assessed experienced homonegativity and related factors (e.g. internalised homonegativity). We focus this analysis on qualitative interviews in which a subset of participants (n = 28) described factors that they perceived to have placed them at risk for HIV infection. Inductive content analysis identified themes within qualitative interviews, and we determined the prevalence of homonegativity and related factors using questionnaires. In qualitative interviews, participants reported that young MSM commonly experienced homonegativity. They described how homonegativity generated internalised homonegativity, HIV stigma, silence around homosexuality, and forced housing displacement. These factors could promote HIV risk. Homonegative experiences were more common among young Black (vs. non-Black) MSM who completed questionnaires. Results illustrate multiple pathways through which experienced homonegativity may increase HIV vulnerability among young MSM. Interventions that target homonegativity might help to reduce the burden of HIV within this population.

Population Size Estimates for Men who Have Sex with Men and Persons who Inject Drugs.

Understanding geographic variation in the numbers of men who have sex with men (MSM) and persons who inject drugs (PWID) is critical to targeting and scaling up HIV prevention programs, but population size estimates are not available at generalizable sub-national levels. We analyzed 1999-2010 National Health and Nutrition Examination Survey data on persons aged 18-59 years. We estimated weighted prevalence of recent (past 12 month) male-male sex and injection drug use by urbanicity (the degree to which a geographic area is urban) and US census region and calculated population sizes. Large metro areas (population ≥1,000,000) had higher prevalence of male-male sex (central areas, 4.4% of men; fringe areas, 2.5%) compared with medium/small metro areas (1.4%) and nonmetro areas (1.1%). Injection drug use did not vary by urbanicity and neither varied by census region. Three-quarters of MSM, but only half of PWID, resided in large metro areas. Two-thirds of MSM and two-thirds of PWID resided in the South and West. Efforts to reach MSM would benefit from being focused in large metro areas, while efforts to reach PWID should be delivered more broadly. These data allow for more effective allocation of funds for prevention programs.

Uptake of Testing for HIV and Syphilis Among Men Who Have Sex with Men in Baltimore, Maryland: 2004-2011.

Men who have sex with men (MSM) in Baltimore are at disproportionately high risk for HIV and syphilis infection. Testing and diagnosis are important first steps in receiving treatment and reducing transmission. We analyzed cross-sectional data collected in 2004-2005, 2008, and 2011 among MSM not reporting a previous positive HIV test (n = 1268) in Baltimore, Maryland as part of the National HIV Behavioral Surveillance System to determine the proportion of men tested for HIV and/or syphilis within the previous 12 months and examine the extent to which opportunities for testing were being missed in health care settings. Within the previous 12 months, 54 % of men had received an HIV test; 31 % had received a syphilis test; and only 23 % of men had received testing for both. Among 979 men who did not receive both tests, 72 % had seen a health care provider in the past year, suggesting missed testing opportunities.

Low viral suppression and high HIV diagnosis rate among men who have sex with men with syphilis--Baltimore, Maryland.

The burden of syphilis and HIV among gay, bisexual, and other men who have sex with men (MSM) in Baltimore, Maryland, is substantial. Syphilis and HIV surveillance data were analyzed to characterize MSM with syphilis, including those with repeat infection and HIV coinfection, to strengthen prevention efforts.

HIV Risk, prevention, and testing behaviors among heterosexuals at increased risk for HIV infection--National HIV Behavioral Surveillance System, 21 U.S. cities, 2010.

At the end of 2010, an estimated 872,990 persons in the United States were living with a diagnosis of human immunodeficiency virus (HIV) infection. Approximately one in four of the estimated HIV infections diagnosed in 2011 were attributed to heterosexual contact. Heterosexuals with a low socioeconomic status (SES) are disproportionately likely to be infected with HIV.

Clinical inquiries regarding Ebola virus disease received by CDC--United States, July 9-November 15, 2014.

Since early 2014, there have been more than 6,000 reported deaths from Ebola virus disease (Ebola), mostly in Guinea, Liberia, and Sierra Leone. On July 9, 2014, CDC activated its Emergency Operations Center for the Ebola outbreak response and formalized the consultation service it had been providing to assist state and local public health officials and health care providers evaluate persons in the United States thought to be at risk for Ebola. During July 9-November 15, CDC responded to clinical inquiries from public health officials and health care providers from 49 states and the District of Columbia regarding 650 persons thought to be at risk. Among these, 118 (18%) had initial signs or symptoms consistent with Ebola and epidemiologic risk factors placing them at risk for infection, thereby meeting the definition of persons under investigation (PUIs). Testing was not always performed for PUIs because alternative diagnoses were made or symptoms resolved. In total, 61 (9%) persons were tested for Ebola virus, and four, all of whom met PUI criteria, had laboratory-confirmed Ebola. Overall, 490 (75%) inquiries concerned persons who had neither traveled to an Ebola-affected country nor had contact with an Ebola patient. Appropriate medical evaluation and treatment for other conditions were noted in some instances to have been delayed while a person was undergoing evaluation for Ebola. Evaluating and managing persons who might have Ebola is one component of the overall approach to domestic surveillance, the goal of which is to rapidly identify and isolate Ebola patients so that they receive appropriate medical care and secondary transmission is prevented. Health care providers should remain vigilant and consult their local and state health departments and CDC when assessing ill travelers from Ebola-affected countries. Most of these persons do not have Ebola; prompt diagnostic assessments, laboratory testing, and provision of appropriate care for other conditions are essential for appropriate patient care and reflect hospital preparedness.

Testing for human immunodeficiency virus among cancer survivors under age 65 in the United States.

Knowing the human immunodeficiency virus (HIV) serostatus of patients at the time of cancer diagnosis or cancer recurrence is prerequisite to coordinating HIV and cancer treatments and improving treatment outcomes. However, there are no published data about HIV testing among cancer survivors in the United States. We sought to provide estimates of the proportion of cancer survivors tested for HIV and to characterize factors associated with having had HIV testing.

HPV vaccine coverage among men who have sex with men - National HIV Behavioral Surveillance System, United States, 2011.

Men who have sex with men (MSM) are at high risk for disease associated with human papillomavirus (HPV). In late 2011, HPV vaccine was recommended for males through age 21 and MSM through age 26. Using data from the 2011 National HIV Behavioral Surveillance System, we assessed self-reported HPV vaccine uptake among MSM, using multivariate analysis to calculate adjusted prevalence ratios (aPRs) and 95% confidence intervals (CIs). Among 3221 MSM aged 18-26, 157 (4.9%) reported ≥1 vaccine dose. Uptake was higher among men who visited a healthcare provider (aPR 2.3, CI: 1.2-4.2), disclosed same-sex sexual attraction/behavior to a provider (aPR 2.1, CI: 1.3-3.3), reported a positive HIV test (aPR 2.2, CI: 1.5-3.2), or received hepatitis vaccine (aPR 3.9, CI: 2.4-6.4). Of 3064 unvaccinated MSM, 2326 (75.9%) had visited a healthcare provider within 1 year. These national data on HPV vaccine uptake among MSM provide a baseline as vaccination recommendations are implemented.

Increases in HIV testing among men who have sex with men--National HIV Behavioral Surveillance System, 20 U.S. Metropolitan Statistical Areas, 2008 and 2011.

In 2011, 62% of estimated new HIV diagnoses in the United States were attributed to male-to-male sexual contact (men who have sex with men, MSM); 39% of these MSM were black or African American. HIV testing, recommended at least annually by CDC for sexually active MSM, is an essential first step in HIV care and treatment for HIV-positive individuals. A variety of HIV testing initiatives, designed to reach populations disproportionately affected by HIV, have been developed at both national and local levels. We assessed changes in HIV testing behavior among MSM participating in the National HIV Behavioral Surveillance System in 2008 and 2011. We compared the percentages tested in the previous 12 months in 2008 and 2011, overall and by race/ethnicity and age group. In unadjusted analyses, recent HIV testing increased from 63% in 2008 to 67% in 2011 overall (P<0.001), from 63% to 71% among black MSM (P<0.001), and from 63% to 75% among MSM of other/multiple races (P<0.001); testing did not increase significantly for white or Hispanic/Latino MSM. Multivariable model results indicated an overall increase in recent HIV testing (adjusted prevalence ratio [aPR] = 1.07, P<0.001). Increases were largest for black MSM (aPR = 1.12, P<0.001) and MSM of other/multiple races (aPR = 1.20, P<0.001). Among MSM aged 18-19 years, recent HIV testing was shown to increase significantly among black MSM (aPR = 1.20, P = 0.007), but not among MSM of other racial/ethnic groups. Increases in recent HIV testing among populations most affected by HIV are encouraging, but despite these increases, improved testing coverage is needed to meet CDC recommendations.

Did CDC's 2006 revised HIV testing recommendations make a difference? Evaluation of HIV testing in the US household population, 2003-2010.

To examine changes in the prevalence of HIV testing among adults following the Centers for Disease Control and Prevention's 2006 revised HIV testing recommendations.

In response to surveillance of HIV in the United States and England, Wales, and Northern Ireland: what have we learned and what do we do about it?