Insecticide Spraying Needed To Control Yellow Fever In Paraguay And Brazil

Africa Fighting Malaria | 26 Feb 2024
Medical News Today
National health authorities have reported the first cases of yellow fever in Paraguay. In the past two months, the number of cases reported by neighboring Brazilian health authorities has more than quadrupled, and deaths have more than doubled 2007 annual figures to 13 - though local media suggests the number of deaths may be as high as 16.

The risk of yellow fever is growing in South America, threatening the return of devastating epidemics that traumatized vast populations of the Americas during the first half of the 20th century. According to local media, the resurgence is causing panic among urban populations of Paraguay, which have mobilized demonstrations and demanded to be vaccinated against the disease.

Yellow fever is a viral disease transmitted by Aedes and Haemagogus mosquitoes. Although an effective vaccine has existed for 60 years, there is no cure for the disease. The World Health Organization estimates that there are 200,000 cases of yellow fever each year and 30,000 deaths.

Mass vaccinations are now underway in Paraguay and Brazil. It will be difficult, if not impossible, for the vaccination program to move quickly enough to prevent additional infections and deaths. Though the outbreaks in Paraguay and Brazil have caused relatively few deaths, there is still cause for concern.

If the outbreaks spread beyond their present endemic zone to large urban population centers lacking sufficient vaccination coverage, the threats could rise exponentially, endangering the lives of thousands more people.

Additionally, history has shown vaccinations alone are insufficient to prevent outbreaks of this mosquito-borne disease. Improved vector control (mosquito control) is urgently needed along with increased surveillance. Vector control programs succeeded at eradicating Aedes aegypti, the urban vector of yellow fever, from most of South America throughout the 1950s, 60s, and much of the 70s. These programs have since lapsed, allowing Aedes aegypti populations to re-invade and proliferate. These mosquitoes also brought dengue fever - and the growing risk of urban yellow fever.

"Vector control programs that eradicated the yellow fever mosquito from most of the Americas were dismantled largely due to anti-insecticides campaigns waged by environmentalist groups," said Dr. Donald Roberts, Professor Emeritus of Tropical Medicine at the Uniformed Services University for the Health Sciences. "The ruinous outbreaks of dengue fever and the growing risk of urban yellow fever in South America is a clear example of the harm these campaigns have caused by not considering the risks of vector-borne diseases."

There are two types of yellow fever found in South America: sylvatic and urban. Sylvatic yellow fever, also known as jungle yellow fever, occurs in tropical forests and is spread among monkeys and mosquitoes. Humans become infected when they enter forested areas and are bitten by infected mosquitoes. Urban yellow fever occurs in urban areas and is spread among humans.

"As with malaria, the yellow fever outbreaks highlight the urgent need for carefully controlled insecticide spraying programs," said Richard Tren, Director of Africa Fighting Malaria, a health advocacy group based in South Africa and Washington, D.C. "These programs should have been strengthened to sustain progress. Decades of anti-insecticides pressure culminated in 1997 when the World Health Assembly passed a resolution to reduce the use of insecticides in disease control. The resurgence of yellow fever is an unfortunate consequence of that resolution."

"The pressure to replace insecticides with politically-correct approaches to disease control, such as environmental management for mosquito elimination, has left populations at great risk of terrible diseases. Anti-insecticide advocacy not only eliminated effective disease prevention programs, it also eliminated investments to find new insecticides," said Dr. Roberts. "We are relying on old tools and the cast offs of the agricultural sector. It is time to set aside entrenched anti-insecticide ideology that dominates the decisions of funding agencies. We need new appropriations to rebuild U.S. expertise in discovery of new insecticides. This includes research and development of new spatial repellents that function, as DDT functions, by keeping mosquitoes out of houses and possibly away from sites where they lay eggs."

More information on yellow fever is available at the websites of the World Health Organization ( and the Pan American Health Organization (

Africa Fighting Malaria (AFM) is a non-profit health advocacy group founded in 2000 and based in South Africa and the United States. Our mission is to make malaria control more transparent, responsive and effective. We conduct research into the social and economic aspects of malaria and raise the profile of the disease and the issues surrounding its control in the local and international media. AFM strives to hold public institutions accountable for funding and implementing effective, integrated and country-driven malaria control policies and to promote successful private sector initiatives to control the disease.

Because of the nature of our work, we do not accept funding from governments, insecticide manufacturers or the pharmaceutical industry. A list of our funders is available on our website at