Current risks of transfusion-transmitted agents: a review

CONTEXT

Infectious disease testing has dramatically improved the safety of blood for transfusion in the United States, especially since the introduction in 1999 of nucleic acid amplification testing. In 2004, methods (primarily culturing) for detecting bacteria in platelets were also added.

OBJECTIVE

To provide current risk estimates for the likelihood of viral transmission by test-negative blood components and to illustrate the safety improvements since the introduction of bacterial testing of platelets.

DATA SOURCES

Published literature from 1999 through 2006 and unpublished American Red Cross data sources.

CONCLUSIONS

The risk of human immunodeficiency virus and hepatitis C virus transmission through blood transfusion since the introduction of nucleic acid amplification testing is approximately 1 in 2 million. Hepatitis B virus risk, for which nucleic acid amplification testing is not performed routinely, remains at 1 in 200,000 to 500,000 using a combination of anti-hepatitis B core and hepatitis B surface antigen testing. Seven cases of transfusion-transmitted West Nile virus have been reported since the introduction of nucleic acid amplification testing in 2003, but none has been reported since system-wide implementation of processes to increase the test sensitivity for use in epidemic areas. The residual risk of receiving a bacterially contaminated platelet component with clinical consequences is estimated at approximately 1 in 75,000, if culture negative and 1 in 33,000 if not tested by culture methods.

Human ecology in pathogenic landscapes: two hypotheses on how land use change drives viral emergence

The emergence of novel viral diseases is driven by socioeconomic, demographic and environmental changes. These include land use changes such as deforestation, agricultural expansion and habitat degradation. However, the links between land use change and disease emergence are poorly understood and probably complex. In this review, we propose two hypotheses for the mechanisms by which land use change can lead to viral emergence: firstly, by perturbing disease dynamics in multihost disease systems via impacts on cross-species transmission rates (the 'perturbation' hypothesis); and secondly, by allowing exposure of novel hosts to a rich pool of pathogen diversity (the 'pathogen pool' hypothesis). We discuss ways by which these two hypotheses might be tested using a combination of ecological and virological approaches, and how this may provide novel control and prevention strategies.

Sharps injuries in UK health care: a review of injury rates, viral transmission and potential efficacy of safety devices

AIMS

To review the literature on sharps injuries and occupational bloodborne virus transmission in health care in the UK and the worldwide evidence for injury prevention of sharps safety devices.

METHODS

Literature review by online database and Internet resource search.

RESULTS

Twenty-four relevant publications were identified regarding UK reported sharps injury rates. UK studies showed as much as a 10-fold difference between injuries reported through standard reporting systems (0.78-5.15 per 100 person-years) and rates estimated from retrospective questionnaires of clinical populations (30-284 per 100 person-years). National surveillance data from England, Wales and Northern Ireland gives a rate of 1.43 known hepatitis C virus or human immunodeficiency virus (HIV) transmissions to health care workers per annum. When extrapolated, this suggests an approximate rate of 0.009 such viral transmissions per 1000 hospital beds per annum. Risk of infection from sources with no risk factors is extremely small (less than one in one million for HIV transmission based on Scottish data). Thirty-one studies on the efficacy of sharps safety devices showed evidence of a reduction in injuries, with the greatest reductions achieved by blunt suture needles and safety cannulae.

CONCLUSIONS

Although injuries remain common, confirmed viral transmission in the UK has been relatively rare. The degree of under-reporting of sharps injuries may be as much as 10-fold. Safety-engineered devices are likely to be effective at injury reduction.

Risking risk: the influence of types of capital and social networks on the injection practices of drug users

Although syringe exchange and other harm reduction interventions have generally been effective in reducing bloodborne pathogen incidence among injection drug users (IDUs), in some cases a minority of IDUs continues to engage in risky injection behavior. Building on emerging perspectives in social epidemiology and research on drug use in anthropology that point to the importance of examining fundamental social causes of risk behavior, or what puts individuals at risk for risk, this study used a multilevel perspective to explore whether forms of capital, social network characteristics, and other contextual factors influence continued risky injection behavior. Quantitative and qualitative data were collected on IDUs in the city of Marseilles, France, where sterile injection equipment has been legal and officially promoted since 1995. In multivariate analysis on data concerning active users, location in the densest part of a large, interconnected network of IDUs greatly increased the likelihood of risky injection practices, while there was a non-significant tendency for low Acquired Cultural and Economic Capital to predict this behavior. Among the strongest individual-level characteristics to predict this outcome were illicit use of prescribed medication, generally high dose buprenorphine, and unprotected sex. Parental abuse of psychoactive drugs during the subject's childhood, on the other hand, greatly decreased the chances of engaging in risky injection behavior. Additionally, qualitative data analysis suggests that risky injection may be linked to lack of resources to procure drugs, and not simply to inadequate sterile injection equipment. Further research, including ecological models, is needed to better understand how fundamental social conditions are related to "risk for risk". However, public health interventions can already address the need for community-level interventions, while rethinking the consequences of inaccessible drugs and unintended "leakage" from the introduction of buprenorphine and other medicalized treatments for opiate dependency.

Epidemiological and experimental studies on a new incident of transmissible mink encephalopathy

Epidemiological investigation of a new incident of transmissible mink encephalopathy (TME) in Stetsonville, Wisconsin, U.S.A. in 1985 revealed that the mink rancher had never fed sheep products to his mink but did feed them large amounts of products from fallen or sick dairy cattle. To investigate the possibility that this occurrence of TME may have resulted from exposure to infected cattle, two Holstein bull calves were injected intracerebrally with mink brain from the Stetsonville ranch. Each bull developed a fatal spongiform encephalopathy 18 and 19 months after inoculation, respectively, and both bovine brains passaged back into mink were highly pathogenic by either intracerebral or oral inoculation. These results suggest the presence of a previously unrecognized scrapie-like infection in cattle in the United States.

Natural vertical transmission of dengue virus in Aedes aegypti and Aedes albopictus: a systematic review

Dengue is of great concern in various parts of the world, especially in tropical and subtropical countries where the mosquito vectors Aedes aegypti and Aedes albopictus are present. The transmission of this virus to humans, by what is known as horizontal transmission, occurs through the bite of infected females of one or other of the two mosquito species. Furthermore, an infected female or male parent, by what is known as vertical transmission, can transfer this arbovirus to some part of their offspring. Considering that vertical transmission may represent an important strategy for maintaining the circulation of arboviruses in nature, the verification of this phenomenon worldwide is extremely important and necessary to better understand its dynamic. In the present study, we conducted a literature review of the presence of natural vertical transmission of dengue virus in Ae. aegypti and Ae. albopictus worldwide. Searches were conducted in MEDLINE, sciELO and Lilacs and all the studies published in Portuguese, English and Spanish were read, evaluated and organized by mosquito species, serotype and the location at which the samples were collected. Forty-two studies were included in accordance with the exclusion criteria and methodology. The presence of natural vertical transmission in Ae. aegypti and Ae. albopictus was most clearly evidenced by dengue virus in endemic countries, especially in those in South America and Asia. Despite several African countries being considered endemic for dengue, there is a lack of publications on this subject on that continent, which highlights the importance of conducting studies there. Furthermore, the finding of natural vertical transmission in Ae. albopictus in countries where this species is not yet incriminated as a vector is of great concern as it demonstrates the circulation of this virus in populations of Ae. albopictus and alerts to the possibility of some other mosquito species playing a role in the transmission dynamics of this arbovirus. Parallel to this, the small number of studies of natural vertical transmission of chikungunya and Zika virus in the world may be explained by the recent entry of these arboviruses into most of the countries concerned.

Evolution of the global burden of viral infections from unsafe medical injections, 2000-2010

Background

In 2000, the World Health Organization estimated that, in developing and transitional countries, unsafe injections accounted for respectively 5%, 32% and 40% of new infections with HIV, hepatitis B virus (HBV) and hepatitis C virus (HCV). Safe injection campaigns were organized worldwide. The present study sought to measure the progress in reducing the transmission of these viruses through unsafe injections over the subsequent decade.

Methods

A mass action model was updated, to recalculate the number of injection-related HIV, HCV and HBV infections acquired in 2000 and provide estimates for 2010. Data about the annual number of unsafe injections were updated. HIV prevalence in various regions in 2000 and 2010 were calculated from UNAIDS data. The ratio of HIV prevalence in healthcare settings compared to the general population was estimated from a literature review. Improved regional estimates of the prevalence of HCV seropositivity, HBsAg and HBeAg antigenemia were used for 2000 and 2010. For HIV and HCV, revised estimates of the probability of transmission per episode of unsafe injection were used, with low and high values allowing sensitivity analyses.

Results

Despite a 13% population growth, there was a reduction of respectively 87% and 83% in the absolute numbers of HIV and HCV infections transmitted through injections. For HBV, the reduction was more marked (91%) due to the additional impact of vaccination. While injections-related cases had accounted for 4.6%–9.1% of newly acquired HIV infections in 2000, this proportion decreased to 0.7%–1.3% in 2010, when unsafe injections caused between 16,939 and 33,877 HIV infections, between 157,592 and 315,120 HCV infections, and 1,679,745 HBV infections.

Conclusion

From 2000 to 2010, substantial progress was made in reducing the burden of HIV, HCV and HBV infections transmitted through injections. In some regions, their elimination might become a reasonable public health goal.

Norwalk gastroenteritis: a community outbreak associated with bakery product consumption

From 23 to 26 August 1982, a gastrointestinal illness occurred among 129 of 248 (52%) persons interviewed who had attended four social events in the Minneapolis-St. Paul area. The median incubation period was 36 hours, and symptoms included diarrhea, nausea, headache, and vomiting. Findings of a food-specific questionnaire given to attendants of the four events confirmed that consumption of cake and frosting was significantly associated with development of the illness (odds ratio, 7.9 to 48.3; p = 0.006 to 0.00001). All cake items were purchased from a single bakery, where the employee who had prepared the frosting had had onset of diarrhea and vomiting on August 20. Given an approximate 60% attack rate among persons who ate frosted items, we estimate that 3000 outbreak-associated cases occurred. Serologic analysis confirmed that 17 of 25 ill persons had fourfold or greater rises in their antibody titer to Norwalk virus. Thus, foodborne transmission of Norwalk virus can result from contamination by a single foodhandler.

Astrovirus infection in volunteers

An extract and a filtrate prepared from feces of a child with mild gastroenteritis were shown by electron microscopy to contain numerous astrovirus particles and were given to eight volunteers by mouth. One subject developed diarrheal illness and concurrently shed large amounts of astrovirus in feces, and one other had mild constitutional symptoms with a lower level of virus shedding. Nine other volunteers were given fecal filtrate from the volunteer with diarrhea, and astrovirus shedding subsequently occurred in two of them. The syndrome accompanying virus shedding appeared distinct from that associated with the "W" agent in previous experiments. Thirteen of 16 astrovirus-inoculated subjects subsequently developed a rise in titer of the homologous antibody in serum. It was concluded that astrovirus causes a transmissible infection that is of low pathogenicity for adults. Immunofluorescence of human embryo kidney cells inoculated with astrovirus and shown by electron microscopy to contain 28 nm virus-like particles was used both to detect virus in feces and to assay astrovirus antibody.

Significant impact of nationwide SARS-CoV-2 lockdown measures on the circulation of other respiratory virus infections in Austria

BACKGROUND

Since the worldwide spread of SARS-CoV-2, different European countries reacted with temporary national lockdowns with the aim to limit the virus transmission in the population. Also Austria started a lockdown of public life in March 2020.

OBJECTIVES

In this study we investigated whether the circulation of different respiratory virus infections in Austria, as assessed by the established respiratory virus surveillance system, is affected by these measures as well and may reflect the success of the lockdown in limiting respiratory virus transmission.

STUDY DESIGN

Sentinel data obtained for influenza virus, respiratory syncytial virus, human metapneumovirus and rhinovirus cases were analyzed and compared between the season 2019/2020 and the five previous seasons.

RESULTS

We observed a rapid and statistically significant reduction of cumulative cases for all these viruses within short time after the lockdown in March 2020, compared to previous seasons (each p < 0.001). Also, sentinel screening for SARS-CoV-2 infections was performed and a decrease of SARS-CoV-2 was seen after the lockdown. While for the seasonally occurring viruses as influenza, respiratory syncytial virus or human metapneumovirus the lockdown led to the end of the annual epidemics, a re-increase of rhinovirus infections was observed after liberalization of numerous lockdown measures.

CONCLUSIONS

Our data provide evidence that occurrence of different respiratory virus infections reflect not only the efficiency of lockdown measures taken against SARS-CoV-2 but it shows also the effects of lockdown releases on the transmission of respiratory viruses.

Emerging infectious diseases that threaten the blood supply

Following the devastating effects of blood-transmitted human immunodeficiency virus (HIV), blood establishments have become increasingly vigilant for the emergence or re-emergence of new threats to the safety of the blood supply. Many agents have fulfilled the broad definition of emerging blood-transmitted infections, including West Nile virus (WNV), Trypanosoma cruzi, Plasmodium spp., Babesia spp., parvovirus B19, dengue virus, and the prions that cause variant Creutzfeld-Jacob disease (vCJD). Other agents such as human herpes virus-8 (HHV-8-Kaposi's sarcoma virus) and Borellia (Lyme disease) and, perhaps, avian flu virus, are known to have a viremic phase, but have not yet been proved to be transfusion-transmitted. In the wake of these threats, transfusion services use a variety of donor screening interventions, including serologic assays, nucleic acid assays, and geographic exclusions based on potential exposure. The ultimate safeguard may be a pre-emptive pathogen inactivation strategy that will disrupt all nucleic acid-containing agents (though not prions). Considerable effort and resources have been invested in this arena, but currently no single technique is effective for inactivation of both liquid and cellular blood products and toxicity issues have not been completely resolved. The blood supply is remarkably safe with the risk of major pathogens such as hepatitis C virus (HCV) and HIV now reduced to less than one transmission per 2 to 3 million exposures. However, to approach near-zero infectious disease risk for emerging and re-emerging pathogens, new strategies such as pathogen inactivation or multi-pathogen microarray technology will need to be developed or refined.

Medically assisted reproduction in the presence of chronic viral diseases

Teams practising medically assisted reproduction techniques try to avoid viruses as much as possible. Attitudes towards chronic carriers of viruses are rapidly changing, especially for human immunodeficiency virus (HIV) patients. We focus our attention on the legitimacy of systematic screening before assisted reproductive techniques and the need for specialized approaches including an adapted laboratory for viral hazards as well as the need for a multidisciplinary team. Specificities of HIV, hepatitis C virus (HCV), hepatitis B virus (HBV) carriers and the hypothesis of a reduced fertility potential are discussed. Are male HIV carriers a new indication for assisted reproductive techniques in order to prevent virus transmission? It is largely proven that sperm gradient preparation techniques efficiently decrease viral loads and therefore have a protective effect on contamination risk during assisted reproductive techniques. Although a few thousand assisted reproductive technique cycles were performed in the world for this indication without contamination, it is still too early to demonstrate that this technology is fully safe. Two examples of contaminations during insemination are examined. Many questions remain unresolved, such as the lack of standardized techniques for semen preparation or virus detection or the relative merits of intrauterine insemination or ICSI to prevent HIV contamination during assisted reproductive techniques. The authors plead for well-structured, separate programmes of care linked to research objectives.

Molecular constraints to interspecies transmission of viral pathogens

The successful replication of a viral pathogen in a host is a complex process involving many interactions. These interactions develop from the coevolution of pathogen and host and often lead to a species specificity of the virus that can make interspecies transmissions difficult. Nevertheless, viruses do sporadically cross species barriers into other host populations, including humans. In zoonotic infections, many of these interspecies transfer events are dead end, where transmission is confined only to the animal-to-human route but sometimes viruses adapt to enable spread from human to human. A pathogen must overcome many hurdles to replicate successfully in a foreign host. The viral pathogen must enter the host cell, replicate with the assistance of host factors, evade inhibitory host products, exit the first cell and move on to the next, and possibly leave the initial host and transmit to another. Each of these stages may require adaptive changes in the pathogen. Although the factors that influence each stage of the replication and transmission of most agents have not been resolved, the genomics of both hosts and pathogens are now at hand and we have begun to understand some of the molecular changes that enable some viruses to adapt to a new host.

Exposure to feline and canine pathogens in bobcats and gray foxes in urban and rural zones of a national park in California

Exposure of bobcats (Lynx rufus) and gray foxes (Urocyon cinereoargenteus) to a range of common canine and feline pathogens was assessed in urban and rural zones of Golden Gate National Recreation Area, a National Park in the San Francisco Bay Area, (California, USA) from 1992 to 1995. Testing included serology for canine distemper virus, canine parvovirus (CPV), canine adenovirus, Leptospira interrogans, feline calicivirus (FCV), feline panleukopenia virus, feline herpesvirus, feline enteric coronavirus (FECV), feline immunodeficiency virus, feline leukemia virus, Toxoplasma gondii, and Bartonella henselae. Testing was also performed for Dirofilaria immitis. Significantly more gray foxes were seropositive for CPV in the urban zone than in the rural zone. In addition, radio-tracking of gray foxes in the rural zone indicated that all three of the rural CPV-seropositive foxes had traveled into adjoining small towns, whereas only one of the 11 seronegative animals had done so. Significantly more bobcats were seropositive for FCV in the rural zone than in the urban zone. Individual bobcats with positive FCV antibody titers had patterns of movement that intercepted park inholdings where domestic cats lived. Bobcat samples were seronegative for all five of the other viral feline pathogens, with the exception of a FECV-seropositive bobcat. High seroprevalence was detected for B. henselae and T. gondii in both zones. Variation in the seroprevalence for different pathogens might be related to differences in the exposure of bobcats and foxes to domestic animals: in the urban zone, gray foxes were located in residential areas outside the park, whereas bobcats were not. Although for most of the pathogens examined there was no relationship between urbanization and exposure, our results for CPV in foxes and FCV in bobcats indicated that proximity to urban areas or contact with humans can increase the risk of disease exposure for wild carnivore populations. Combining behavioral information from radio-tracking with data on pathogen exposure or disease incidence can provide valuable insights into the ecology of wildlife disease that might be missed with broad-scale, population-level comparisons alone.

The global burden of bacterial and viral zoonotic infections

Bacterial and viral zoonotic infections comprise a practically endless, ever-expanding list of pathogens that have the potential to induce human disease of varying severity, with varying means of transmission to humans (including vector-borne and foodborne agents) and of varying epidemiology. Not all theoretically zoonotic pathogens are truly zoonotic in practice, the prime example being influenza viruses; aviann H5N1 influenza remains strictly zoonotic, whereas novel H1N1 influenza displays an anthropocentric cycle that led to a pandemic, despite being of zoonotic origin. The burden of disease induced by zoonotic and viral pathogens is enormous: there are more than ten bacterial zoonoses, each of which affects hundreds of thousands patients annually, often leading to chronic infections and causing significant economic losses of a medical and livestock-related nature. Viral zoonotic agents are constantly emerging or re-emerging, and are associated with outbreaks of limited or expanded geographical spread: the typical trends of viral zoonotic infections, however, is to extend their ecological horizon, sometimes in an unexpected but successful manner, as in the case of West Nile virus, and in other instances less effectively, as was the case, fortunately, in the case of avian influenza. The majority of bacterial and viral zoonotic infections attract disproportionately low scientific and public health interest. Understanding their burden may allow for improved surveillance and prevention measures.