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Introduction
Gregory C. Gray MD, MPH is a Professor in Infectious Disease Epidemiology in the Departments of Internal Medicine (Infectious Diseases), Microbiology & Immunology, Global Health & Emerging Diseases at the University of Texas Medical Branch in Galveston, Texas.
Professor Gray received his medical degree, at the University of Alabama at Birmingham, School of Medicine, Birmingham, Alabama, his Masters in Public Health degree from Johns Hopkins School of Hygiene & Public Heal
Current institution
Additional affiliations
January 2010 - July 2014
Publications
Publications (505)
In February 2024, while conducting surveillance for novel respiratory viruses, we studied four beef cattle farms near Monterrey, Mexico. Nasal swabs were collected from sick and healthy beef cattle along with 3 h aerosol samples. None of the samples had molecular evidence of influenza A viruses. Three (8%) of thirty-six nasal swabs collected from t...
Background Adenoviruses have caused epidemics among both humans and poultry in Pakistan. There is growing evidence that adenoviruses sometimes spillover to infect other species. In this pilot study, we sought to study the distribution of circulating adenovirus types among humans, poultry and other animals in several areas of Pakistan. Methods From...
Background
In early April 2024 we studied 2 Texas dairy farms that had suffered incursions of H5N1 highly pathogenic avian influenza virus (HPAIV) the previous month.
Methods
We employed molecular assays, cell and egg culture, Sanger and next generation sequencing to isolate and characterize viruses from multiple farm specimens (cow nasal swab, mi...
In this report, we sought to demonstrate that freshwater sampling for migrating bird-associated novel respiratory virus incursions is possible and more desirable than the alternative approach of capturing and swabbing wild migrating birds. Freshwater sampling should be considered as an alternative approach for pre-pandemic pathogen surveillance.
Background: In early April 2024 we studied two Texas dairy farms which had suffered incursions of H5N1 highly pathogenic avian influenza virus (HPAIV) the previous month.
Methods: We employed molecular assays, cell and egg culture, Sanger and next generation sequencing to isolate and characterize viruses from multiple farm specimens (cow nasal swab...
Background
In recent years, Vietnam has suffered multiple epizootics of influenza in poultry.
Methods
From 10 January 2019 to 26 April 2021, we employed a One Health influenza surveillance approach at live bird markets (LBMs) and swine farms in Northern Vietnam. When the COVID-19 pandemic permitted, each month, field teams collected oral secretion...
During March and April 2024, we studied dairy cattle specimens from a single farm in Texas, USA, using multiple molecular, cell culture, and next-generation sequencing pathogen detection techniques. Here, we report evidence that highly pathogenic avian influenza A(H5N1) virus strains of clade 2.3.4.4b were the sole cause of this epizootic.
This study used metagenomics to identify respiratory viruses in cattle, farm workers, and environments in US and Mexico.
Our study objective was to use a One Health approach in studying livestock farms to monitor for novel coronaviruses and influenza viruses that could represent spillover events.
This prospective, longitudinal, community-based study, EpidemiologiCal POpulatioN STudy of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in Lake CounTy, Illinois (CONTACT), investigated coronavirus disease 2019 (COVID-19) immunity, occupational risks related to SARS-CoV-2 exposure, and long-term immunoglobulin G (IgG) seroconversion...
Since the 1990s, multiple infectious diseases have "spilled over" from nonhuman animals to infect humans and cause significant global morbidity and mortality. Despite efforts to detect and respond to such threats, surveillance and mitigation efforts have been criticized as ineffective. This article describes what "spillover" and "spillback" events...
Due to the extensive host range of influenza A viruses, it is difficult to determine the best diagnostic algorithm to efficiently screen samples from a variety of host species for influenza A viruses. While there are some influenza diagnostic algorithms that are specific to host species, to our knowledge, no single algorithm exists for the characte...
Background:
Zoonotic influenza surveillance in Myanmar is sparse, despite the risks of introduction of such viruses from neighboring countries that could impact the poultry industry and lead to spillover to humans.
Methods:
In July and August 2019, our multi-institutional partnership conducted a One Health-oriented, cross-sectional surveillance...
Although cattle are a reservoir for influenza D virus (IDV), little is known about human exposure to IDV. We assessed IDV exposure and associated health effects among United States dairy workers, a population at heightened risk of cattle zoonoses. In prospective, cross‐shift sampling of 31 workers employed at five large‐herd dairy operations in two...
Background
Pigs are unique reservoirs for virus ecology. Despite the increased use of improved biosecurity measures, pig viruses readily circulate in Chinese swine farms.
Objectives
The main objective of this study was to examine archived swine oral secretion samples with a panel of pan‐species viral assays such that we might better describe the v...
Texas is a geographically large state with large human and livestock populations, many farms, a long coastal region, and extreme fluctuations in weather. During the last 15 years, the state of Texas has frequently suffered disasters or catastrophes causing extensive morbidity and economic loss. These disasters often have complicated consequences re...
The aeromicrobiological transmission pathway of enteric pathogens in places with unsafe sanitation services is poorly understood. In an attempt to partly fill this knowledge gap, we assessed the potential public health impact of bioaerosols near open waste canals (OWCs) using Quantitative Microbial Risk Assessment (QMRA). We used data acquired in L...
Since the beginning of the SARS‐CoV‐2 pandemic, antibody responses and antibody effector functions targeting SARS‐CoV‐2‐infected cells have been understudied. Consequently, the role of these types of antibodies in SARS‐CoV‐2 disease (COVID‐19) and immunity is still undetermined. To provide tools to study these responses, we used plasma from SARS‐Co...
Here we review the existing evidence of animal alphacoronaviruses (Alphacoronavirus 1 species) circulating in human patients with acute respiratory illness. Thus far, the viruses similar to canine, feline and porcine alphacoronaviruses (including the most recent CCoV-HuPn-2018 and HuCCoV_Z19) have been detected in humans in Haiti, Malaysia, Thailan...
Introduction:
EpidemiologiCal POpulatioN STudy of SARS-CoV-2 in Lake CounTy, Illinois (CONTACT) is an observational, epidemiological study with a 9-month longitudinal follow-up of nonhospitalized persons aged 18 years or older currently living or employed in Lake County, IL. We describe the study design and report baseline characteristics of the s...
We assessed environmental contamination of inpatient rooms housing COVID-19 patients in a dedicated COVID-19 unit. Contamination with SARS-CoV-2 was found on 5.5% (19/347) of surfaces via RT-PCR and 0.3% (1/347) of surfaces via cell culture. Environmental contamination is uncommon in hospitals rooms; RNA presence is not a specific indicator of infe...
Introduction
Streptococcus suis is a zoonotic pathogen found in swine that may cause systemic infection in humans. S. suis is endemic in Southeast Asia and is the leading cause of adult meningitis in Vietnam. Given Vietnam's increasing centralization of the swine industry, we sought to estimate the prevalence of S. suis on large swine farms in Nort...
An increasing body of literature suggests that aerosol inhalation plays a primary role in COVID-19 transmission, particularly in indoor settings. Mechanistic stochastic models can help public health professionals, engineers, and space planners understand the risk of aerosol transmission of COVID-19 in order to mitigate it. We developed such model a...
Background
Leptospirosis diagnoses have increased in Sarawak, Malaysia in recent years.
Methods
To better understand the burden of disease and associated risk factors, we evaluated 147 patients presenting with clinical leptospirosis to local hospitals in Sarawak, Malaysia for the presence of Leptospira and associated antibodies. Sera and urine spe...
The livestock industry in Mongolia accounts for 24% of national revenue, with one third of the population maintaining a pastoral lifestyle. This close connection between Mongolian population and livestock is a major concern for pathogen transfer, especially given the increase in vector-borne diseases globally. This study examines blood samples from...
Modern day large-scale, high-density farming environments are inherently susceptible to viral outbreaks, inadvertently creating conditions that favor increased pathogen transmission and potential zoonotic spread. Metagenomic sequencing has proven to be a useful tool for characterizing the microbial burden in both people, livestock, and environmenta...
Background
Human Adenoviruses (HAdVs) cause a wide array of illnesses in all age groups. They particularly cause frequent morbidity among children. In China, human adenovirus types 3, 4, 7, 11, 14, 21, and 55 have caused at least seven outbreaks since 2000. However, limited studies are available regarding the epidemiological patterns and diversity...
Background
Cryptosporidium spp. and Giardia duodenalis are important zoonotic enteric pathogens of One Health concern for humans, animals, and the environment. For this study, we investigated parasite prevalence and risk factors among rural, peri-urban, and urban households and environments of Mongolia.
Methods
This cross-sectional study implement...
Growth in pork production during the last decade in South Africa has escalated the risk of zoonotic pathogen emergence. This cross-sectional study was conducted to evaluate evidence for cross-species transmission of influenza A virus between pigs and swine workers. Between February and October 2018, samples from swine workers and pigs were collecte...
We examined a collection of 386 animal, 451 human, and 109 archived bioaerosol samples with a new pan-species coronavirus molecular assay. Thirty-eight (4.02%) of 946 specimens yielded evidence of human or animal coronaviruses. Our findings demonstrate the utility of employing the pan-CoV RT-PCR assay in detecting varied coronavirus among human, an...
Antiviral therapeutics are a front-line defense against virally induced diseases. Because viruses frequently mutate to escape direct inhibition of viral proteins, there is interest in targeting the host proteins that the virus must co-opt to complete its replication cycle. However, a detailed understanding of the interactions between the virus and...
Background
During the validation of a highly sensitive pan-species coronavirus (CoV) semi-nested RT-PCR assay, we found canine CoV (CCoV) RNA in nasopharyngeal swabs from eight (2.5%) of 301 patients hospitalized with pneumonia during 2017-18 in Sarawak, Malaysia. Most patients were children living in rural areas with frequent exposure to domestica...
Despite many recent efforts to predict and control emerging infectious disease threats to humans, we failed to anticipate the zoonotic viruses which led to pandemics in 2009 and 2020. The morbidity, mortality, and economic costs of these pandemics have been staggering. We desperately need a more targeted, cost-efficient, and sustainable strategy to...
Background Human Adenoviruses (HAdVs) cause a wide array of illnesses in all age groups. They particularly cause frequent morbidity among children. In China, human adenovirus types 3, 4, 7, 11, 14, 21, and 55 have caused at least seven outbreaks since 2000. However, limited studies are available regarding the epidemiological patterns and diversity...
Influenza viruses are an important cause of disease in both humans and animals, and their detection and characterization can take weeks. In this study, we sought to compare classical virology techniques with a new rapid microarray method for the detection and characterization of a very diverse, panel of animal, environmental, and human clinical or...
Human adenovirus type 4 (HAdV-E4) frequently causes epidemics among military and civilian populations. We conducted a systematic review of 144 peer-reviewed articles reporting HAdV-E4 infections, published during the years 1960 – 2020. More than 24,500 HAdV-E4 infections, including 27 associated deaths, were documented. HAdV-E4 infections were repo...
In this paper we review recent human respiratory virus epidemics, their zoonotic nature, and our current inability to identify future prepandemic threats. We propose a cost-efficient, One Health surveillance strategy that will be more efficient and more sustainable than previous efforts.
Dengue is a rapidly spreading mosquito-borne flavivirus infection that is prevalent in tropical and sub-tropical regions. Humans are known to be the main reservoir host maintaining the epidemic cycles of dengue but it is unclear if dengue virus is also maintained in a similar enzootic cycle. The systematic review was conducted in accordance to Coch...
Abstract In 2018, our team collected aerosols samples from five poultry farms in Malaysia. Influenza D virus was detected in 14% of samples. One sample had an 86.3% identity score similar to NCBI accession number MH785020.1. This is the first molecular sequence of influenza D virus detected in Southeast Asia from a bioaerosol sample. Our findings i...
The strong bond between herder and livestock was forged centuries ago in rural Mongolia and remains an element of national pride and a cornerstone to the economy. However, semi-nomadic herders frequently live at the edge of human health care, veterinary services, and municipal infrastructure like water and sanitation. This study examined zoonotic r...
Abstract
Objectives: To determine aetiology of illness among children and adults presenting during outbreak of severe respiratory illness in Southern Province, Sri Lanka, in 2018.
Design: Prospective, cross-sectional study.
Setting: 1600-bed, public, tertiary care hospital in Southern Province, Sri Lanka.
Participants: 410 consecutive patients,...
During April and May 2020, we studied 20 hospitalized COVID-19 patients, their hospital rooms (fomites and aerosols), and their close contacts for molecular and culture evidence of SARS-CoV-2 virus. Among the more than 400 samples, we found molecular evidence of virus in most sample types, especially the nasopharygeal (NP), saliva, and fecal sample...
Background:
In a year-long pneumonia etiology study conducted June 2017 to May 2018 in Sarawak, Malaysia, 599 patients' nasopharyngeal swab specimens were studied with real-time polymerase chain reaction (rPCR)/ reverse-transcription (rRT-PCR) assays for respiratory pathogens known to contribute to the high burden of lower respiratory tract infect...
Despite close contact between humans and animals on large scale farms, little to no infectious disease research is conducted at this interface. Our goal in this preliminary study was to explore if we could detect swine pathogens using a non-invasive, indirect approach through the study of swine slurry. From April to November 2018, 105 swine slurry...
Disease outbreaks can readily threaten swine production operations sometimes resulting in large economic losses. Pathogen surveillance within swine farms can be an effective approach for the early identification of new disease threats and the mitigation of transmission before broad dissemination among a herd occurs. Non‐invasive environmental bioae...
Understanding the particle size distribution in the air and patterns of environmental contamination of SARS-CoV-2 is essential for infection prevention policies. Here we screen surface and air samples from hospital rooms of COVID-19 patients for SARS-CoV-2 RNA. Environmental sampling is conducted in three airborne infection isolation rooms (AIIRs)...
Severe acute respiratory illness (SARI) is a major cause of death and morbidity in low- and middle-income countries, however, the etiologic agents are often undetermined due to the lack of molecular diagnostics in hospitals and clinics. To examine evidence for select viral infections among patients with SARI in northern Vietnam, we studied 348 naso...
Evidence of exposure to enteric pathogens through the air and associated risk of infection is scarce in the literature outside of animal- or human-waste handling settings. Cities with poor sanitation are important locations to investigate this aerial exposure pathway as their rapid growth will pose unprecedented challenges in waste management. To a...
During 2018, we conducted periodic bioaerosol sampling at a live bird market in Kunshan China and found (55%) of 120 samples to have evidence of avian influenza virus. We recovered four live viruses through egg culture. These results support the effectiveness of noninvasive bioaerosol sampling in live animal markets.
Background: Understanding the particle size distribution in the air and patterns of environmental contamination of SARS-CoV-2 is essential for infection prevention policies.
Objective: To detect the surface and air contamination by SARS-CoV-2 and study the associated patient-level factors.
Design: Cross-sectional study.
Setting: Airborne infection...
Background
During the past two decades, three novel coronaviruses (CoVs) have emerged to cause international human epidemics with severe morbidity. CoVs have also emerged to cause severe epidemics in animals. A better understanding of the natural hosts and genetic diversity of CoVs are needed to help mitigate these threats.
Objective
To design and...
Background:
Worldwide, horses play critical roles in recreation, food production, transportation, and as working animals. Horses' roles differ by geographical region and the socioeconomic status of the people, but despite modern advances in transportation, which have in some ways altered humans contact with horses, potential risks for equine zoonot...
The One Health approach has received widespread international endorsements from professional, academic, and governmental organizations as the way forward in tackling complex interdisciplinary problems, such as emerging zoonotic diseases, antimicrobial resistance, and food safety. Yet conspicuously absent from US One Health training or research acti...
Due to their overall immunocompromised state, lung transplant recipients (LTRs) are at increased risk for the development of viral respiratory infections compared to the general population. Such respiratory infections often lead to poor transplant outcomes. We performed a systematic review of the last 30 years of medical literature to summarize the...
We measured antibodies against H7N9 virus 2 years after infection in 14 patients who were infected during October 2016-September 2017. Approximately 2 years after infection, antibody titers ≥10 were detectable in 13 (92.9%) patients. Three (21.4%) of 14 patients had hemagglutination inhibition titers ≥40, and their geometric mean titer (GMT) was 20...
Given their lack of immunity and increased exposure, military personnel have the potential to serve as carriers or reservoirs for infectious diseases into or out of the deployment areas, but, to our knowledge, the historical evidence for such transmission events has not previously been reviewed. Using PubMed, we performed a systematic review of pub...
There is an increasing body of evidence suggesting that transmission of respiratory viruses occurs through the inhalation of virus-laden particles. Our study describes the use of an aerosol sampling system to monitor the prevalence of airborne viruses in a hospital setting. Using SKC AirCheck Touch pumps, with National Institute for Occupational Sa...
Burkholderia pseudomallei infections are prevalent in Southeast Asia and northern Australia and often misdiagnosed. Diagnostics are often neither sensitive nor rapid, contributing up to 50% mortality rate. In this 2018 pilot study, we enrolled 100 patients aged 6 months-79 years from Kapit Hospital in Sarawak, Malaysia, with symptoms of B. pseudoma...
Adenoviruses (AdVs) are major contributors to clinical illnesses. Novel human and animal AdVs continue to be identified and characterized. Comparative analyses using bioinformatic methods and Omics-based technologies allow insights into how these human pathogens have emerged and their potential for host cross-species transmission. Systematic review...
Background:
A number of serious human adenovirus (HAdV) outbreaks have been recently reported: HAdV-B7 (Israel, Singapore, and USA), HAdV-B7d (USA and China), HAdV-D8, -D54, and -C2 (Japan), HAdV-B14p1 (USA, Europe, and China), and HAdV-B55 (China, Singapore, and France).
Methods:
To understand the epidemiology of HAdV infections in Singapore, w...
Background:
China is thought to be a hotspot for zoonotic influenza virus emergence, yet there have been few prospective studies examining the occupational risk of such infections.
Methods:
We present the first two years of data collected from a five-year, prospective cohort study of swine-exposed and unexposed participants, pigs, and six swine...
Here we review evidence for influenza A viruses (IAVs) moving from swine, avian, feline, equine, and canine species to infect humans. We review case reports, sero-epidemiological, archeo-epidemiological, environmental, and historical studies and consider trends in livestock farming. Although this focused review is not systematic, the aggregated dat...
A hospital outbreak of human parainfluenza virus type 3 (HPIV-3) in haematologic oncology patients is described in 12 patients over a four-week period. Exposure histories and molecular analysis of HPIV-3 isolates suggest that both community-acquired and nosocomially transmitted infections occurred during this outbreak. Molecular analysis of HPIV-3...
Equine influenza virus (EIV) is a common, highly contagious equid respiratory disease. Historically, EIV outbreaks have caused high levels of equine illness and economic damage. Outbreaks have occurred worldwide in the past decade. The risk for EIV infection is not limited to equids; dogs, cats, and humans are susceptible. In addition, equids are a...
Since the first outbreak of avian influenza A(H7N9) virus in China in early 2013, a number of interventions to control the transmission of H7N9 virus from poultry to humans have been implemented. Temporary closing live poultry markets reduced the risk of human infection to an extent, but it did not prevent the spread of the H7N9 virus among poultry...
Twenty‐six per cent of Mongolians live pastoral lifestyles, increasing their likelihood of exposure to ticks and placing them at a higher risk for contracting tick‐borne diseases (TBDs). Anaplasma spp. and Rickettsia spp. have been identified in ticks, livestock and humans in Mongolia, but no known qualitative research has been conducted investigat...
Background
Though pneumonia is a known cause of morbidity and mortality in Sarawak, Malaysia, the etiology and epidemiology of pneumonia are not well described in this equatorial region. Routine clinical diagnostics for pneumonia etiology at government hospitals in Sarawak had historically involved only bacterial diagnostics. Viral diagnostics were...
Mongolia has more than ten times as many livestock as people. Herders are dependent on their livestock for their livelihood, and seasonal movement is driven by the livestock’s grazing needs. The daily, seasonal interactions between Mongolian herders and their livestock put herders at risk for several zoonotic diseases. The goals of this pilot study...