The escalation of dengue fever incidence in Latin America – with more than 1.1 million cases reported in 2012 [Figure 1] – poses a serious public health threat to the millions of people living in the region. Recently, health authorities in Brazil reported that more than 200,000 people were infected with dengue fever in the first seven weeks of 2013 compared with 70,000 in the same period last year, indicating a steep rise in confirmed cases.
The rise in dengue fever has made this disease the #1 vector-borne infection in Latin America. Public health efforts to control dengue have been challenging due to serious systemic factors, including rapid urban population growth, inadequate financial resources, under-appreciation of the seriousness of the disease, and lack of political will to undertake prevention efforts.
Figure 1: Reported Dengue Cases in the Americas, 2012.
Source: Pan American Health Organization.
Beyond political and economic factors, the dengue problem is exacerbated by climatic factors in the Americas, such as heavy rainfall. In the Atlas of Health and Climate, dengue fever was described as a “climate-sensitive disease” that becomes more pronounced when hard rains hit. Going back to at least 1998, a clear correlation has been noted between incidence of dengue fever and heavy rainfall in tropical and subtropical regions. Heavy rainfall causes standing water, and encourages people to keep more water around the home to deal with future shortages – both of which create more breeding areas for the Aedes mosquitoes that transmit dengue.
To reduce the burden of disease, Latin American countries will need to coordinate social and environmental efforts that embrace vector management and an effective vaccination program once a safe and effective vaccine becomes available. The success of these efforts will depend on firm political and social commitment both at the local and national level.
Collapse of Dengue Control Efforts
The first suspected dengue-like epidemics first emerged in the Americas in the 1600s, and by the 1800s, were common in port cities across the region, from the Caribbean to South America. Into the 1900s, outbreaks were increasingly common and sometimes widespread, including an extended outbreak in Miami in 1934 that impacted about 10% of the population and also spread throughout Florida and south Georgia. The first mosquito eradication effort was in 1901 in Cuba, and by the mid-20th century, only one dengue virus strain (DENV-2, genotype V) seemed to be in circulation.
Unfortunately, the fruits of these decades of efforts deteriorated rapidly, as eradication efforts lost political importance in countries where dengue was no longer a major public health issue. Other factors contributing to the collapse of dengue control efforts included an increasing lack of sanitation in urban areas, and development of mosquito resistance to pesticides, to name a few.
The number of reported dengue cases increased considerably in the early 1980s; one of the worst outbreaks of that period (Cuba, 1981) resulted in excess of 344,000 cases [Figure 2]. Over the ensuing decades, Brazil has been especially hard hit, while Colombia also has reported a consistently high number of cases, though Mexico, Paraguay, Cuba, and others have been subject to large outbreaks in recent years.
Figure 2. Dengue Outbreaks in the Americas, 2008-2010.
Source: Brathwaite Dick, et al, Am J.Trop. Med Hyg.
The year 2010 brought a major, pan-American epidemic [Figure 3] that resulted in a staggering 1.7 million cases (including 50,000+ clinically severe cases) in this single year. The most significant outbreaks were in Colombia (the worst outbreak in its history with 157,000+ reported cases), Venezuela, Brazil, and Honduras, along with several Caribbean nations.
High levels of dengue cases have persisted into 2012, with an alarming 1.1 million cases of dengue fever reported last year in Latin America, including more than 31,000 severe cases. All told, the number of cases in this region has increased almost 5-fold since the 1980s.
Figure 3. Dengue Incidence in the Americas -- 1980-2010.
Source: PAHO 2011.
Dengue is Not the Problem of “Others” – Prevention and Control Challenges
Unfortunately, morbidity and mortality statistics on dengue are often imprecise, leading some public health officials to underestimate the magnitude of this issue. As a result, dengue becomes a problem of “others” that is shunted off to neighboring communities, government agencies, or municipalities. Instead, political commitment is needed to face the problem directly. The Pan American Health Organization (PAHO) and World Health Organization (WHO) have called on member states in the Americas to strengthen prevention and patient care while improving the training of health care workers to identify individuals at risk of developing severe disease and needing hospital care.
There are helpful resources available, including recent guidelines for dengue diagnosis and treatment in the Americas region. The guidelines include recommendations that can be applied even in areas where resources are limited, and offers a stepwise method for dengue management, from vector control to severe dengue case management in a hospital setting.
Critical Needs Now and Tomorrow
To reduce the burden of dengue in the coming years, an integrated prevention and control strategy will be needed. This strategy should include a rapid diagnostic and care management plan to reduce both the incidence of severe dengue and mortality related to the disease. Community participation along with vector control and personal prevention measures are the other components of this strategy, which will be complemented in the near future by a safe and effective vaccine, once it becomes available.