-
Trends in Immunology Dec 2020The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) marks the third highly pathogenic coronavirus to spill over into the human population.... (Review)
Review
The emergence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) marks the third highly pathogenic coronavirus to spill over into the human population. SARS-CoV-2 is highly transmissible with a broad tissue tropism that is likely perpetuating the pandemic. However, important questions remain regarding its transmissibility and pathogenesis. In this review, we summarize current SARS-CoV-2 research, with an emphasis on transmission, tissue tropism, viral pathogenesis, and immune antagonism. We further present advances in animal models that are important for understanding the pathogenesis of SARS-CoV-2, vaccine development, and therapeutic testing. When necessary, comparisons are made from studies with SARS to provide further perspectives on coronavirus infectious disease 2019 (COVID-19), as well as draw inferences for future investigations.
Topics: Animals; COVID-19; Humans; SARS-CoV-2
PubMed: 33132005
DOI: 10.1016/j.it.2020.10.004 -
Nature Reviews. Microbiology Aug 2021Human respiratory virus infections lead to a spectrum of respiratory symptoms and disease severity, contributing to substantial morbidity, mortality and economic losses... (Review)
Review
Human respiratory virus infections lead to a spectrum of respiratory symptoms and disease severity, contributing to substantial morbidity, mortality and economic losses worldwide, as seen in the COVID-19 pandemic. Belonging to diverse families, respiratory viruses differ in how easy they spread (transmissibility) and the mechanism (modes) of transmission. Transmissibility as estimated by the basic reproduction number (R) or secondary attack rate is heterogeneous for the same virus. Respiratory viruses can be transmitted via four major modes of transmission: direct (physical) contact, indirect contact (fomite), (large) droplets and (fine) aerosols. We know little about the relative contribution of each mode to the transmission of a particular virus in different settings, and how its variation affects transmissibility and transmission dynamics. Discussion on the particle size threshold between droplets and aerosols and the importance of aerosol transmission for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and influenza virus is ongoing. Mechanistic evidence supports the efficacies of non-pharmaceutical interventions with regard to virus reduction; however, more data are needed on their effectiveness in reducing transmission. Understanding the relative contribution of different modes to transmission is crucial to inform the effectiveness of non-pharmaceutical interventions in the population. Intervening against multiple modes of transmission should be more effective than acting on a single mode.
Topics: Aerosols; COVID-19; Humans; Hygiene; Personal Protective Equipment; SARS-CoV-2
PubMed: 33753932
DOI: 10.1038/s41579-021-00535-6 -
Acta Medica Portuguesa Dec 2019Over the last few decades, behavioral changes in sexual practices have made oral transmission of traditional sexually transmissible infections increasingly recognized.... (Review)
Review
Over the last few decades, behavioral changes in sexual practices have made oral transmission of traditional sexually transmissible infections increasingly recognized. Patients harboring a sexually transmissible infection may first present lesions on the oral cavity, as these may be visible and interfere with basic functions such as speech or swallowing. Moreover, the oral cavity may function as a reservoir for future spread of these infections. In order to successfully control this problem, a greater focus on oral sex should be persued, along with promotion of the use of condom and education on safe oral sex practices. Furthermore, examination of the oral cavity should is essential when evaluating any patient suspected of harboring a sexually transmissible infection. In this article, oral transmission of several viral and bacterial infections is reviewed, including human papillomavirus infection, genital herpes, syphilis and gonorrhea, among others.
Topics: Chlamydia Infections; Chlamydia trachomatis; Gonorrhea; HIV Infections; Herpes Simplex; Humans; Mouth Diseases; Papillomavirus Infections; Safe Sex; Sexual Behavior; Sexually Transmitted Diseases; Syphilis
PubMed: 31851887
DOI: 10.20344/amp.12191 -
Current Opinion in Pulmonary Medicine May 2023The coronavirus disease 2019 pandemic has had a wide-ranging and profound impact on how we think about the transmission of respiratory viruses This review outlines the... (Review)
Review
PURPOSE OF REVIEW
The coronavirus disease 2019 pandemic has had a wide-ranging and profound impact on how we think about the transmission of respiratory viruses This review outlines the basis on which we should consider all respiratory viruses as aerosol-transmissible infections, in order to improve our control of these pathogens in both healthcare and community settings.
RECENT FINDINGS
We present recent studies to support the aerosol transmission of severe acute respiratory syndrome coronavirus 2, and some older studies to demonstrate the aerosol transmissibility of other, more familiar seasonal respiratory viruses.
SUMMARY
Current knowledge on how these respiratory viruses are transmitted, and the way we control their spread, is changing. We need to embrace these changes to improve the care of patients in hospitals and care homes including others who are vulnerable to severe disease in community settings.
Topics: Humans; SARS-CoV-2; COVID-19; Respiratory Aerosols and Droplets; Pandemics
PubMed: 36866737
DOI: 10.1097/MCP.0000000000000947 -
Virus Research Dec 2013Highly pathogenic avian H5N1 influenza A viruses occasionally infect humans and cause severe respiratory disease and fatalities. Currently, these viruses are not... (Review)
Review
Highly pathogenic avian H5N1 influenza A viruses occasionally infect humans and cause severe respiratory disease and fatalities. Currently, these viruses are not efficiently transmitted from person to person, although limited human-to-human transmission may have occurred. Nevertheless, further adaptation of avian H5N1 influenza A viruses to humans and/or reassortment with human influenza A viruses may result in aerosol transmissible viruses with pandemic potential. Although the full range of factors that modulate the transmission and replication of influenza A viruses in humans are not yet known, we are beginning to understand some of the molecular changes that may allow H5N1 influenza A viruses to transmit via aerosols or respiratory droplets among mammals. A better understanding of the biological basis and genetic determinants that confer transmissibility to H5N1 influenza A viruses in mammals is important to enhance our pandemic preparedness.
Topics: Animals; Humans; Influenza A Virus, H5N1 Subtype; Influenza, Human; Mammals; Orthomyxoviridae Infections
PubMed: 23954580
DOI: 10.1016/j.virusres.2013.07.017 -
International Journal of Infectious... Nov 2020The persistence and intensity of the current severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic, and the advanced planning required to balance... (Review)
Review
The persistence and intensity of the current severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) pandemic, and the advanced planning required to balance competing concerns of saving lives and avoiding economic collapse, may depend in part on whether the virus is sensitive to seasonal changes in environmental variables, such as temperature and humidity. Although multiple studies have sought to address possible effects of these variables on SARS-CoV-2 transmission, results of these studies have been varied. It is possible that at least some of the differing results are due to insufficient understanding of atmospheric science, including certain physical and chemical principles underlying selected meteorological variables, and how global seasons differ between tropical and temperate zones. The objective of this brief perspective is to provide information that may help explain some of the differing results of studies regarding the influence of environmental variables on transmissibility of SARS-CoV-2. This information may promote better variable selection and results interpretation in future studies of coronavirus disease 2019 (COVID-19) and other infectious diseases.
Topics: COVID-19; Humans; Humidity; Pandemics; SARS-CoV-2; Seasons; Weather
PubMed: 32950732
DOI: 10.1016/j.ijid.2020.09.032 -
Transfusion Medicine Reviews Jan 2008No transmission through transfusion has been reported for classic Creutzfeldt-Jakob disease (CJD). Moreover, a series of epidemiological surveillance, case-control, and... (Review)
Review
No transmission through transfusion has been reported for classic Creutzfeldt-Jakob disease (CJD). Moreover, a series of epidemiological surveillance, case-control, and look-back studies have provided no evidence of such transmission of CJD. Hence, the risk of such transfusion transmission of classic CJD remains theoretical. In contrast, based on data from the United Kingdom, the likelihood of transmission of the agent of the variant form of CJD (vCJD) through blood transfusion by donors who develop the disease within several years of donation is about 14% for recipients who survive longer than 5 years posttransfusion. Leukodepletion may reduce the likelihood of vCJD transmissions, although this procedure by itself removes less than half of the prion infectivity of blood. The potentially longer incubation periods of vCJD with infections in donors who are not methionine/methionine homozygous at codon 129 of the prion protein gene, the unknown number of such donors, and the unknown infectivity of their blood during the incubation period suggests caution in assuming that only known cases of vCJD represent a risk for the transfusion transmission of vCJD. Results from ongoing look-back investigations and other studies will enable continued monitoring and more precise estimations of the risks of the transfusion transmission of CJD and vCJD.
Topics: Animals; Creutzfeldt-Jakob Syndrome; Humans; Incidence; Mass Screening; Prion Diseases; Public Health; Transfusion Reaction
PubMed: 18063192
DOI: 10.1016/j.tmrv.2007.09.003 -
Current Topics in Microbiology and... 2014Influenza A viruses cause yearly epidemics and occasional pandemics. In addition, zoonotic influenza A viruses sporadically infect humans and may cause severe... (Review)
Review
Influenza A viruses cause yearly epidemics and occasional pandemics. In addition, zoonotic influenza A viruses sporadically infect humans and may cause severe respiratory disease and fatalities. Fortunately, most of these viruses do not have the ability to be efficiently spread among humans via aerosols or respiratory droplets (airborne transmission) and to subsequently cause a pandemic. However, adaptation of these zoonotic viruses to humans by mutation or reassortment with human influenza A viruses may result in airborne transmissible viruses with pandemic potential. Although our knowledge of factors that affect mammalian adaptation and transmissibility of influenza viruses is still limited, we are beginning to understand some of the biological traits that drive airborne transmission of influenza viruses among mammals. Increased understanding of the determinants and mechanisms of airborne transmission may aid in assessing the risks posed by avian influenza viruses to human health, and preparedness for such risks. This chapter summarizes recent discoveries on the genetic and phenotypic traits required for avian influenza viruses to become airborne transmissible between mammals.
Topics: Animals; Birds; Humans; Influenza A virus; Influenza in Birds; Influenza, Human; Mammals; Orthomyxoviridae Infections; Swine; Swine Diseases
PubMed: 25048542
DOI: 10.1007/82_2014_387 -
Journal of Epidemiology Feb 2022A measles outbreak involving 60 cases occurred in Yamagata, Japan in 2017. Using two different mathematical models for different datasets, we aimed to estimate measles...
BACKGROUND
A measles outbreak involving 60 cases occurred in Yamagata, Japan in 2017. Using two different mathematical models for different datasets, we aimed to estimate measles transmissibility over time and explore any heterogeneous transmission patterns.
METHODS
The first model relied on the temporal distribution for date of illness onset for cases, and a generation-dependent model was applied to the data. Another model focused on the transmission network. Using the illness-onset date along with the serial interval and geographical location of exposure, we reconstructed a transmission network with 19 unknown links. We then compared the number of secondary transmissions with and without clinical symptoms or laboratory findings.
RESULTS
Using a generation-dependent model (assuming three generations other than the index case), the reproduction number (R) over generations 0, 1, and 2 were 25.3, 1.3, and <0.1, respectively, explicitly yielding the transmissibility over each generation. The network data enabled us to demonstrate that both the mean and the variance for the number of secondary transmissions per primary case declined over time. Comparing primary cases with and without secondary transmission, high viral shedding was the only significant determinant (P < 0.01).
CONCLUSIONS
The R declined abruptly over subsequent generations. Use of network data revealed the distribution of the number of secondary transmissions per primary case and also allowed us to identify possible secondary transmission risk factors. High viral shedding from the throat mucosa was identified as a potential predictor of secondary transmission.
Topics: Disease Outbreaks; Humans; Japan; Measles; Models, Theoretical; Risk Factors
PubMed: 33281152
DOI: 10.2188/jea.JE20200455 -
The Journal of Infectious Diseases Mar 2022The Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the predominant variant worldwide at the time of this study. However, its...
BACKGROUND
The Delta variant of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the predominant variant worldwide at the time of this study. However, its transmission dynamics were unclear.
METHODS
We analyzed 405 local cases infected with the Delta variant of SARS-CoV-2 and temporal patterns of viral shedding identified between 22 June and 31 July 2021 in Daejeon, South Korea.
RESULTS
Overall, 20% were presymptomatic at the time of epidemiological investigation. We identified 6 clustered outbreaks, and all were associated with indoor facilities. In 23 household contacts, the secondary attack rate was 63%. We estimated the mean serial interval as 3.26 days (95% credible interval, 2.92-3.60), and 15% (95% confidence interval, 13%-18%) of cases seeded 80% of all local transmission. Analysis of the nasopharyngeal swab samples identified virus shedding from the presymptomatic cases and the highest viral load was observed 2 days after symptom onset.
CONCLUSIONS
Our findings suggest that the Delta variant is highly transmissible in indoor settings and households. Rapid contact tracing, isolation of the asymptomatic contacts, strict adherence to public health measures, and increased uptake of coronavirus disease 2019 (COVID-19) vaccination, including booster doses, are needed to reduce community transmission of the Delta variant.
Topics: Adolescent; Adult; Aged; COVID-19; Child; Child, Preschool; Communicable Disease Control; Contact Tracing; Disease Outbreaks; Female; Humans; Incidence; Infant; Infant, Newborn; Male; Middle Aged; Republic of Korea; Reverse Transcriptase Polymerase Chain Reaction; SARS-CoV-2; Virus Shedding
PubMed: 34865022
DOI: 10.1093/infdis/jiab586