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Health Sweden



Extremely high temperatures become increasingly common, leading to a higher mortality rate for vulnerable groups such as the sick and the elderly. An increased frequency of flooding increases the risk of the spread of infection, including through water washing over pasture land and sewage overflow. A warmer climate also means an increased risk of new and existing diseases spreading (1).

Cold and heat stress

When Europe was struck by a severe heat wave in August 2003, it is estimated that more than 33,000 people died as a direct consequence of the heat.

Depending on the current climate and on local adaptation, the optimum temperature from a health perspective, i.e. in this case the lowest number of deaths, is different in different parts of the world. In Finland, the optimum temperature has been calculated at 14°C, in London around 20°C and in Athens around 25°C (1).

The first Swedish study into how temperature and heat waves affect mortality has recently been conducted, focusing on 41 communities within Greater Stockholm with some 1.1 million inhabitants between 1998–2003 (2). It is estimated that the number of deaths per year in Sweden in heat waves will have increased by just over 1,000 by the end of this century. The decrease in the number of really cold days results in reduced mortality, but this effect is smaller.

The number of deaths due to cold and hot extreme temperatures attributable to climate change was estimated for Stockholm by comparing data on temperature and mortality for 1900-1929 and 1980-2009 (20). Cold extremes were defined such that they correspond with temperatures below – 6.3°C; heat corresponds to temperatures above 19.6°C. Results adjusted for urbanization and heat island effects show that there was a small increase in extreme cold temperature-related mortality and a substantial increase in extreme heat temperature-related mortality in 1980-2009 as compared with 1900-1929. Not adjusting for urbanization and heat island effects, there was a small decrease in extreme cold temperature mortality in 1980-2009 compared with 1900-1929, with a much larger increase in extreme hot temperature mortality (20). Future changes in the frequency and intensity of heat waves might be of a magnitude large enough to overwhelm the ability of individuals and communities to adapt. The expected increase in the number of elderly and other potentially vulnerable groups, in absolute numbers and as a proportion of the population, could make the impact of temperature extremes on human health even more severe (21).

Most European countries have between 5 and 30 % higher death rates in winter than in summer. Winter‑related mortality in many European populations has declined since the 1950s (6). Cold days, cold nights and frost days have become rarer, but explain only a small part of this reduction: improved home heating, better general health and improved prevention and treatment of winter infections have played a more significant role (7).

Skin cancer

The stratospheric ozone layer over the Arctic is not expected to improve significantly for at least a few decades, largely due to the effect of greenhouse gasses on stratospheric temperatures. Ultraviolet radiation (UV) in the Arctic is thus projected to remain elevated in the coming decades (3). Increased UV is known to cause skin cancer, cataracts, and immune system disorders in humans.

Tick-borne diseases

Between the early 1980s and mid-1990s in Sweden a northward expansion of the geographic distribution limit of the disease-transmitting tick Ixodes ricinus and an increased tick density has been reported. Researchers related this expansion to climatic changes. They concluded that the relatively mild climate of the 1990s in Sweden is probably one of the primary reasons for the observed increase of density and geographic range of I. ricinus ticks (4).

The winters were markedly milder in all of the study areas in the 1990s as compared to the 1980s. Research has shown that the reported northern shift in the distribution limit of ticks is related to fewer days during the winter seasons with low minimum temperatures, i.e., below -12°C. At high latitudes, low winter temperatures had the clearest impact on tick distribution. Further south, a combination of mild winters (fewer days with minimum temperatures below -7°C) and extended spring and autumn seasons (more days with minimum temperatures from 5 to 8°C) was related to increases in tick density (4).

The findings indicate that the increase in tick-borne encephalitis (TBE) incidence in Sweden since the mid-1980s is related to the period's change towards milder winters and early arrival of spring. Other factors may have influenced TBE incidence such as more people in endemic locations, and increases in host animal populations; factors which are partly climate related. Access to TBE vaccination since 1986 and increased awareness of ticks might have caused an underestimation of the links found (5).

In the Alps and Scandinavia increased winter mean temperatures at higher altitudes and latitudes and an extended vegetation period may have permitted roe deer to spread to and inhabit previously inhospitable areas. Such deer movements may have allowed this tick to be transported northwards on the Scandinavian Peninsula, resulting in a significantly increased tick range during the last 30 years (26). Changes in forest and wildlife management probably also played a role (25). In Sweden, the northward spread of this tick to many previously tick-free localities was particularly rapid and extensive. This was probably due to a combination of the expansion of the roe deer population and the warmer climate (mild winters and extended spring and autumn seasons) (26). 

In the future, the distribution of the tick I. ricinus is projected to expand in Northern Europe as winter seasons become shorter and milder, and deciduous woodland expands. Tick density and infection risk will probably also increase due to an increase in the density of wild and domestic vertebrates, paralleled with the expansion of suitable habitats for the host animals of ticks (24). 

Mosquito-borne diseases

While climatic factors may favor autochthonous transmission, increased vector density, and accelerated parasite development, other factors (socioeconomic, building codes, land use, treatment, etc) limit the likelihood of climate related re-emergence of malaria in Europe (8).

Sand-fly-borne diseases

Leishmaniasis is a protozoan parasitic infection caused by Leishmania infantum that is transmitted to human beings through the bite of an infected female sandfly. Sandfly distribution in Europe is south of latitude 45⁰N and less than 800 m above sea level, although it has recently expanded as high as 49⁰N. Currently, sandfly vectors have a substantially wider range than that of L infantum, and imported cases of infected dogs are common in central and northern Europe. Once conditions make transmission suitable in northern latitudes, these imported cases could act as plentiful source of infections, permitting the development of new endemic foci. Conversely, if climatic conditions become too hot and dry for vector survival, the disease may disappear in southern latitudes. Thus, complex climatic and environmental changes (such as land use) will continue to shift the dispersal of leishmaniasis in Europe (8).


Floods are the most common natural disaster in Europe. The adverse human health consequences of flooding are complex and far-reaching: these include drowning, injuries, and an increased incidence of common mental disorders. Anxiety and depression may last for months and possibly even years after the flood event and so the true health burden is rarely appreciated (9).

Effects of floods on communicable diseases appear relatively infrequent in Europe. The vulnerability of a person or group is defined in terms of their capacity to anticipate, cope with, resist and recover from the impact of a natural hazard. Determining vulnerability is a major challenge. Vulnerable groups within communities to the health impacts of flooding are the elderly, disabled, children, women, ethnic minorities, and those on low incomes (9).

Adaptation strategies - General - Heatwaves

The outcomes from the two European heat waves of 2003 and 2006 have been summarized by the IPCC (10) and are summarized below. They include public health approaches to reducing exposure, assessing heat mortality, communication and education, and adapting the urban infrastructure.

1. Public health approaches to reducing exposure

A common public health approach to reducing exposure is the Heat Warning System (HWS) or Heat Action Response System. The four components of the latter include an alert protocol, community response plan, communication plan, and evaluation plan (11). The HWS is represented by the multiple dimensions of the EuroHeat plan, such as a lead agency to coordinate the alert, an alert system, an information outreach plan, long-term infrastructural planning, and preparedness actions for the health care system (12).

The European Network of Meteorological Services has created Meteoalarm as a way to coordinate warnings and to differentiate them across regions (13). There are a range of approaches used to trigger alerts and a range of response measures implemented once an alert has been triggered. In some cases, departments of emergency management lead the endeavor, while in others public health-related agencies are most responsible (14).

2. Assessing heat mortality

Assessing excess mortality is the most widely used means of assessing the health impact of heat-related extreme events.

3. Communication and education

One particularly difficult aspect of heat preparedness is communicating risk. In many locations populations are unaware of their risk and heat wave warning systems go largely unheeded (15). Some evidence has even shown that top-down educational messages do not result in appropriate resultant actions (16).

More generally, research shows that communication about heat preparedness centered on engaging with communities results in increased awareness compared with top-down messages (17).

4. Adapting the urban infrastructure

Several types of infrastructural measures can be taken to prevent negative outcomes of heat-related extreme events. Models suggest that significant reductions in heat-related illness would result from land use modifications that increase albedo, proportion of vegetative cover, thermal conductivity, and emissivity in urban areas (18). Reducing energy consumption in buildings can improve resilience, since localized systems are less dependent on vulnerable energy infrastructure. In addition, by better insulating residential dwellings, people would suffer less effect from heat hazards. Financial incentives have been tested in some countries as a means to increase energy efficiency by supporting those who are insulating their homes. Urban greening can also reduce temperatures, protecting local populations and reducing energy demands (19).

Tick-borne diseases: Lyme and encephalitis (TBE)

Other ways to protect against tick-borne diseases is preventing tick bites, by avoiding tick risk areas, being informed about how to remove ticks and recognize early symptoms, using insect repellent on skin and clothing when in risk areas, and wearing protective clothing with long sleeves, and long trousers tucked into socks or boots (22).

The best way to protect against TBE is vaccination. Austria is among the most strongly affected countries in Central Europe, but the annual number of cases has strongly declined due to vaccination. In Austria, the high vaccination coverage (more than 80% of the total population has received at least one TBE vaccination) has led to a substantial decline in the number of annual cases (23). The incidence in the unvaccinated population, however, remained constant at about 6 per 100,000, suggesting no major changes in the countrywide overall risk of human exposure to TBE virus-infected ticks.

There is currently no vaccine available on the European market for Lyme disease (24). Since ticks do not have a high probability of transmitting the Borrelia bacteria that causes Lyme disease until 12–24 hours after ticks begin to feed on the blood of their host, immediate removal of ticks is one of the most effective ways of avoiding Borrelia infection (24).


The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for Sweden.

  1. Swedish Commission on Climate and Vulnerability (2007)
  2. Rocklöv and Forsberg (2007), in: Swedish Commission on Climate and Vulnerability (2007)
  3. ACIA (2004)
  4. Lindgren et al. (2000)
  5. Lindgren et al. (2001)
  6. Kunst et al. (1991); Lerchl (1998); Carson et al. (2006), in: EEA, JRC and WHO (2008)
  7. Carson et al. (2006), in: EEA, JRC and WHO (2008)
  8. Semenza and Menne (2009)
  9. Hajat et al. (2003)
  10. IPCC (2012)
  11. Health Canada (2010), in: IPCC (2012)
  12. WHO (2007), in: IPCC (2012)
  13. Bartzokas et al. (2010), in: IPCC (2012)
  14. McCormick (2010b), in: IPCC (2012)
  15. Luber and McGeehin (2008), in: IPCC (2012)
  16. Semenza et al. (2008)), in: IPCC (2012)
  17. Smoyer-Tomic and Rainham (2001), in: IPCC (2012)
  18. Yip et al. (2008); Silva et al. (2010), both in: IPCC (2012)
  19. Akbari et al. (2001), in: IPCC (2012)
  20. Åström et al. (2013)
  21. Rocklöv et al. (2011), in: Åström et al. (2013)
  22. WHO (2016)
  23. Heinz et al. (2015)
  24. Rizzoli et al. (2011)
  25. Rizzoli et al. (2009), in: Rizzoli et al. (2011)
  26. Jaenson et al. (2012), in: Medlock et al. (2013)
  27. Åström et al. (2013)