Microbial Variation in Climatic Change and its Effect on Human Health


J. Insira Sarbeen1, Dr. Gheena S2

Saveetha Dental College and Hospital, Chennai

Corresponding Author E-mail : insiraaah237@gmail.com



Aim: The aim of the article is to do a literature review on microbial variation in climatic change and its effect on human health. Objective: The main objective of the article is to review the microbial variation in climatic change and its effect on human health. Background: Each environmental change, whether occurring as a natural phenomenon or through human intervention, changes the ecological balance and context within which disease hosts or vectors and parasites breed, develop, and transmit disease. Each species occupies a particular ecological niche and vector species sub-populations are distinct behaviourally and genetically as they adapt to man-made environments. Conclusion: The article views at highlighting the microbial variation in climatic change and its effect on human health.


KEYWORDS :  Climate Change, Human Health, Microbes, Diseases, Seasonal Change.





Human alteration of the environment has triggered the sixth major extinction event in the history of life and caused changes in the global distribution of organisms. These changes alter ecosystem processes and change the resilience of ecosystems to environmental change. The large ecological and societal consequences of changing biodiversity should be decreased so that to preserve options for future against environmental problems. Humans have greatly altered the global environment, changing global biogeochemical cycles. Fossil-fuel combustion and deforestation have increased atmospheric carbon dioxide (CO2) by  30%. We  have also doubled the concentration of methane and other gases that leads  to global  warming. In the upcoming century these greenhouse gases causes most rapid climate change that the Earth has experienced since the last glaciation 18,000 years ago [1].


The direct  and  indirect  impacts of  these  increases  in greenhouse gas  concentrations on  the oceans  will  cause increase in  temperatures,  acidification, changes the  density structure of the upper ocean which alters  vertical mixing  of waters, weakening  of upwelling winds, and changes  the timing and  volume  of freshwater runoff into coastal marine  waters. The predicted changes in  our  oceans may impact both directly  and indirectly  the interactions between humans and the oceans. Recent studies  have  reviewed oceanic  responses  to  future climate change, the impacts that these changes will have on  human  societies [2]. Annual global temperatures have increased by 0.4◦C since 1980. Understanding the net global impact of recent climate trends would help to anticipate impacts of future climate changes, as well as to more accurately assess recent technologically driven yield progress[3]. Meningococcal meningitis in western Africa shows recurrent seasonal patterns every year. Epidemics typically start at the beginning of February and last until May. We can explain the observed patterns on the basis of seasonally varying environmental factor that aids in  disease transmission [4]. These sorts of extreme weather events reflect massive and ongoing changes in  our climate [5]. Increases in mortality rate and  hospitali-sations  due  to  extreme  heat,  is observed  in well developed and developing  countries and also increases  in  rates  of  injuries and mortality rate due  to  increasing  frequency  of  weather  disasters  in  many  regions. Extensions  in  the  geographic  range  of  several  vector-borne infectious  diseases  or  their  vectors,  including  tick borne  encephalitis  in  Sweden,  the  tick  vector  of  Lyme disease  in  eastern Canada, and malaria in the western Kenyan highlands. Although,  increases  in  the  temperature of  coastal outbreaks  of  cholera  relative  to  the  warming  of  coastal  waters. Increases  in  the  price of  some staple foods,  especially in vulnerable, food-insecure regions, leading to  nutritional  deprivation  in  low-income  households [6]. Globally, infectious diarrhoea is the second-leading cause of death in young children; water-borne gastroenteritis is projected to increase under conditions of global warming [7]. Cholera is a good example of how information concerning environmental factors permits better understanding of the disease not only virulence but equally important transmission and epidemiology [8]. Bacterial meningitis is an infection or inflammation of the protective membranes covering the brain. Several different bacteria are however said to possess the potential to  cause bacterial meningitis and Neisseria meningitidis  is one of the most important because of  its potential to cause  epidemics [9]. Growing concerns over the effects of climate change and environmental deterioration are driving current interest in the influence of climate on disease dynamics. The importance of climatic factors, however, is controversial because of the many human and socioeconomic determinants [1], even for vector-borne diseases such as malaria with well established relations between weather and transmission capacity. Climate and disease associations in the past have lacked quantitative support, certainly for cholera and other diseases with less consensus on environmental drivers [10].



Importance of Seasonality :

At first sight, understanding seasonal patterns seems disconnected from understanding the impact of long-term climate change. However, seasonal patterns are one major pathway for the subtle but potentially drastic effects of climate change on disease dynamics. Long-term climate change affects seasonal patterns through the lengthening of the transmission season and the crossing of environmental and demographic thresholds that underlie seasonal outbreaks. Thus, identifying the specific environmental factors underlying seasonal transmission is a critical step towards predicting and understanding how long-term environmental trends in mean climate and their variability will impact human health [4]. In  the  past  three decades, widening  social  inequities  and changes in  biodiversity which alter the balance among predators,  competitors,  and  prey that  help  keep  pests  and  pathogens  in  check have  apparently contributed to  the resurgence of infectious  diseases.  Global  warming and wider fluctuations  in weather  help  to  spread  these  diseases:  temperature  constrains  the range  of  microbes  and  vectors, and weather affects the timing  and intensity of  disease outbreaks [5].


Weather And Diseases:

The sensitivity to meteorological conditions can manifest in the form of various ailments. The most common is headache, often associated with  state of fatigue. But there are other typical manifestations such as irritability, difficulty concentration and even sleep disorders. It also points of agreement that the seasons influence the onset of certain diseases. The allergists are well aware that bronchial asthma, allergic rhinitis and other disease of the respiratory system have their high points in the spring and autumn, probably due to greater abundance of allergens-pollen, leaf debris, dust -those times of the year. However no known allergic causes such as gastritis and peptic ulcer and nervous system diseases with crises of severe depression or euphoria also have irritation in spring or Autumn [16].


Airborne Particulate Matter and Human Health:

Results of recent research show that particulate matter (PM) composition and size vary widely with both space and time. Despite the variability in PM characteristics, which are believed to influence human health risks, the observed relative health risk estimates per unit PM mass falls within  a narrow range of values. Furthermore, no single chemical species appears to dominate health effects, rather the effects appear to be due to a combination of species. Non-PM factors such as socioeconomic status and lifestyle are also believed to affect the health risk, although accounting for these confounding factors is challenging. Airborne PM is also responsible for a number of effects aside from human health, such as alterations in visibility and climate. The earliest and most methodologically simple studies that evaluated short-term changes in exposure to air pollution focused on severe air pollution episodes. Death counts for several days or weeks were compared before, during, and after the episodes. By the early 1990s, the results of several daily time series studies were reported. These studies did not rely on extreme pollution episodes but evaluated changes in daily mortality counts associated with daily changes in air pollution at relatively low, more common levels of pollution. Because these studies suggested measurable mortality effects of particulate air pollution at relatively low concentrations, there were various questions and concerns that reflected legitimate skepticism about these studies. One question regarding these early daily time series mortality studies was whether or not they could be replicated by other researchers and in other study areas. The original research has been independently replicated and more importantly, comparable associations have been observed in many other cities with different climates, weather conditions, pollution mixes, and    demographics [14].


Implications of Harmful Algal Blooms on Human Health :

Although the adverse health  effects from exposure  to  HA toxins  has been known for  decades (for  some of the cyanobacterial toxins) or more (e.g.,  brevetoxins  associated with Florida red tides), very few  epidemiologic  studies designed to  systematically assess  these effects have been done. Probably the  most widely studied HA  toxins  are the brevetoxins  associated  with Florida red tides. Brevetoxins are a group of polyether toxins that affect sodium channels and can induce bronchoconstriction in the mammalian respiratory  tract. The effects of human exposure to aerosolised breve-toxins have been examined in three  of the  populations most likely to  be susceptible. These  studies  have  shown that healthy  people acutely exposed  to  aerosolised brevetoxins  during  Florida red tide events experience respiratory irritation that  is  reportedly relieved when they leave the beach. People with asthma  are more  susceptible  to brevetoxins, and may experience  both acute  and  more long-term  detriments  in  pulmonary  function [2].


Infectious Diseases:

Globally, infectious diarrhoea is the second-leading cause of death in young children; water-borne gastroenteritis is projected to increase under conditions of global warming [6]. Currently, the World Health Organisation estimates that, approximately 1.62 million children younger than 5 years die of diarrhoea annually, and most cases are attributable to contaminated water. Although children in developed countries are unlikely to die of water-borne infections, they may suffer illness that is attributable indirectly to climate change. Events associated model for global warming by altering weather for periods of several years in the direction of a hotter climate [7].


Vector-Borne Infections:

They are affected by climate change. Both the hosts and the pathogens (eg, bacteria, viruses, parasites) can be sensitive to climatic variables such as temperature, humidity, and rainfall. The ability to predict disease rates related to climate change is complicated by a large number of additional variables such as topography, land use, urbanisation, human population distribution, level of economic development, and public health infrastructure [7]. There is no easy formula that predicts climate change–related infection risk with confidence. Malaria is a climate-sensitive vector-borne illness to which children are particularly vulnerable. Because they lack specific immunity, children experience disproportio nately high levels of both morbidity and mortality from malaria; 75%of malaria deaths occur in children younger than 5 years. The young are also more susceptible to cerebral malaria, which can lead to lifelong neurologic damage in those who survive. More than 3 billion people live in malaria-prone areas today. Climate change is expanding the range of host mosquitoes to higher altitudes and higher latitudes, and warmer temperatures speed the development of the parasite within the host vector. Small children will be most affected by the expansion of malaria zones and the success or failure of societal response to this change [3,6,7] Vector-borne pathogens cause enormous suffering to humans and animals. Many are expanding their range into new areas. Dengue, West Nile and Chikungunya have recently caused substantial human epidemics. Arthropod-borne animal diseases like Bluetongue, Rift Valley fever and African horse sickness pose substantial threats to livestock economies around the world. Climate change can impact the vector-borne disease epidemiology. Changes in climate will influence arthropod vectors, their life cycles and life histories, resulting in changes in both vector and pathogen distribution and changes in the ability of arthropods to transmit pathogens. Climate can affect the way pathogens interact with both the arthropod vector and the human or animal host. Predicting and mitigating the effects of future changes in the environment like climate change on the complex arthropod–pathogen–host epidemiological cycle requires understanding of a variety of complex mechanisms from the molecular to the population level. Although there has been substantial progress on many fronts the challenges to effectively understand and mitigate the impact of potential changes in the environment on vector-borne pathogens are formidable and at an early stage of development [12].


Contagious Infections:

Bacterial meningitis is an infection or inflammation of the protective membranes covering the brain. Several different bacteria are however said to possess the potential to  cause bacterial meningitis and Neisseria meningitidis  is one of the most important because of  its potential to cause  epidemics (the other bacteria, besides  N. meningitidis  (meningococcus) that can  cause bacterial meningitis include  S. pneumoniae  and  H. influenzae  type b). Bacterial meningitis is now said to be among the top 10 infectious causes of death worldwide [8]. Meningeal syndrome, the septic form and pneumonia are  the three main clinical  forms of the disease.  The bacteria causing Cerebrospinal meningitis  has been identified  to be transmitted from person to person through droplets of respiratory or throat   secretions. The bacteria can  be carried in the pharynx and   it overwhelm  the body’s defences. This allows  infection to spread through  the bloodstream  and to   the brain. Conditions that favour transmission of the bacteria  are densely populated rooms  with inadequate ventilation, overcrowding at public events including  worship centres and markets, as well as population movements during pilgrimages. Incubation period ranges  from  2 to 10 days with an average of 4 days, and  N. meningitidis  does not infect animals but only humans [9]. Moist and humid conditions have also long been associated with cholera’s spatial distribution. For example, cholera’s incidence in nine provinces of former British India increases with average annual rainfall [10].


Water Borne Infections :

They exhibit a positive correlation with excess precipitation events, which are likely to increase with climate change; over a 45-year period, 68% of water-borne illness outbreaks have been associated with precipitation. Food borne illness correlates positively with ambient temperature and is also likely to increase as the climate warms [3,6,7]. It concentrates on the impact of two possible changes to climate  increased frequency of heavy rainfall events, with associated flooding and increased temperature. Flooding is associated with increased risk of infection in developing nations but not in the West unless water sources are compromised. There have been numerous reported of outbreaks that followed flooding that led to contamination of underground sources of drinking water. Heavy rainfall also leads to deterioration in the quality of surface waters that could adversely affect the health of those engaged in recreational water contact. It is also concluded that there may be an increase in the number of cyanobacterial blooms because of a combination of increased nutrient concentrations and water temperature. It is considered unlikely that climate change will lead to an increase in disease linked to mains drinking water, although private supplies would be at risk from increased heavy rainfall events. Although increased temperature could lead to climatic conditions favourable to increases in certain vector-borne diseases such as malaria [15].


Human Microbiome:

The majority of microbes reside in the gut, have a profound influence on human physiology and nutrition, and are crucial for human life. Furthermore, the gut microbes contribute to energy harvest from food, and changes of gut microbiome may be associated with bowel diseases or obesity [17]. Studies of the human microbiome have revealed that even healthy individuals differ remarkably in the microbes that occupy habitats such as the gut, skin and vagina. Much of this diversity remains unexplained, although diet, environment, host genetics and early microbial exposure have all been implicated. The Human microbiome project encountered an estimated 81–99% of the genera, enzyme families and community configurations occupied by the healthy Western microbiome. Metagenomic carriage of metabolic pathways was stable among individuals despite variation in community structure, and ethnic/racial background proved to be one of the strongest associations of both pathways and microbes with clinical metadata. These results thus delineate the range of structural and functional configurations normal in the microbial communities of a healthy population, enabling future characterisation of the epidemiology, ecology and translational applications of the human microbiome [18].



The scientific community should intensify its efforts to  identify the causes of nonlinearities and thresholds in the response of ecosystem and social processes to changes in biodiversity. Ensure better health care to include improving the health care infrastructure in developing countries. Institute better surveillance protocols for these diseases throughout the world to quickly bring to bear resources to reduce epidemics. Rapid  globalisation  has  brought  new,  large-scale influences  to  bear  on  patterns  of  human  health. The major cause of change is the rapid release of CO2 from burning of fossil fuel. There are anticipated effects on human health from extreme weather events, infectious diseases, air pollution, and heat stress. An understanding of disease risk related to the environment can also underscore the need for improving these conditions.



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Received on 31.05.2016             Modified on 17.06.2016

Accepted on 01.07.2016           © RJPT All right reserved

Research J. Pharm. and Tech 2016; 9(10):1777-1781.

DOI: 10.5958/0974-360X.2016.00359.0