Climate change and vector‐borne viral diseases potentially transmitted by transfusion

Abstract

Vector‐borne diseases occur when infectious agents (virus, protozoa, bacteria, or helminthes) are transmitted to their hosts by a carrier organism. Climate conditions and their changes play a role in the inter‐relationship between these agents, the vectors and the host (or hosts). This review is focused on arthropod‐borne viruses (Arboviruses). These viruses are transmitted between susceptible vertebrate hosts by blood‐feeding arthropods, and may be transmitted by blood transfusion, tissue and organ transplantation and breast feeding. The lifecycle of arboviruses is influenced by changes in temperature, rainfall, humidity, length of day, average daily solar radiation and/or storm patterns, as well as changes in the frequency of rare events such as floods or droughts. A plethora of studies have suggested that climate changes, particularly temperature changes, are likely to be induced by increase in the amount of greenhouse gases, such as methane, carbon dioxide (CO2) and chlorofluorocarbons, which deplete ozone in the atmosphere leading to an increase in ultraviolet radiation. Current models predict that ambient temperature will increase by 3–5°C on average with a doubling in CO2 concentration in the atmosphere. Vectors, pathogens and hosts each survive and reproduce within a range of optimal climatic conditions: temperature and precipitation being most important, while sea level elevation, wind and daylight duration are also important. Climate changes may affect important determinants of vector‐borne disease transmission including (i) vector survival and reproduction, (ii) the vector's biting rate, and (iii) the pathogen's incubation rate within the vector organism. Droughts can increase the dissemination of arboviral diseases in urban areas by allowing a boost in the population of mosquitoes in foul water concentrated in catch basins where they breed. Furthermore, eggs can be vertically infected with arboviruses and heat waves speed up the maturation of the mosquitoes and of the viruses within mosquitoes. Droughts also cause a decline in mosquito predators like frogs, darning needles and dragonflies. In addition, birds congregate around shrinking water sites, enhancing circulation of viruses among birds and mosquitoes. In conclusion, the seriousness of some of the recent epidemics like West Nile virus and Dengue appear to has been influenced by climate change. As most of the arboviral infections are asymptomatic in humans, there is an increased opportunity for blood, organ and tissue donations by infected individuals during the viraemic period, resulting in an increased risk of transmission of arboviruses.

COMMENTARY: Relative safety of pooled whole blood–derived versus single‐donor (apheresis) platelets in the United States: a systematic review of disparate risks

“…The effect of the impending introduction of minipool nucleic‐acid technology testing for HBV (which is expected to reduce the window period by 5 to 8 days) was not taken into account. Two infectious agents that could emerge in the United States in the future were also considered: 1) an HIV‐like novel pathogen with a long incubation period that could accumulate in the blood donor base before it became recognized (thereby approximating the HIV risk before testing was introduced) and 2) a West Nile virus (WNV)‐like pathogen that could change its geographic distribution 62 and emerge as transfusion‐transmitted in the United States (thereby reproducing the WNV risk in the summer and fall of 2002).…”

“…Overall, if 5% of those asymptomatically infected with WNV in 2002 had donated blood, approximately 380 infectious donations 67 could have been made during the 7‐day period of viremia. Dengue fever virus, 68,69 other arboviruses, 62,70 or other infectious agents such as the agent of Q fever 71,72 may replicate the 2002 WNV experience in the future 8 …”

Emerging infections in Asia and its possible global effects

“…Cases of transfusion transmission have not been reported. Mathematical modelling based on sentinel surveillance data, duration of viraemia and the frequency of asymptomatic infection during an epidemic in Reunion Island in 2005‐07 however suggests that this might occur [10].…”

“…Many other arboviruses exist some of which share features with those of WNV, dengue and chikungunya [10]. This is currently a particular concern to authorities in Australia.…”

Detection of blood‐transmissible agents: can screening be miniaturized?

“…The relationship between potential infectivity and viral load was recently evaluated to accurately estimate the residual risk from these viruses 2 . Nevertheless, blood testing must be able to adapt to the demands of microbiologic safety and thus consider the fact that the engaged offensive against the transmissible agents has not yet finished 3‐12 …”