Yellow fever encircles cities in the Americas

Washington, DC, July 3, 2002 (PAHO) -- More than six decades ago the countries of the Americas joined efforts to get rid of urban yellow fever. Today the Pan American Health Organization (PAHO) is making new appeals to keep this epidemic out of urban areas.

According to PAHO, all cases of yellow fever reported in the region since the 1940s have been of the jungle form of this disease, transmitted by Haemagogus mosquitoes. However, with the rapid spread of the Aedes aegypti mosquito in the region, there is a danger that urban yellow fever could return.

The seriousness of the current yellow fever situation in the Americas requires a firm commitment by countries to a strong, effective strategy to control the disease. The recommendations of PAHO focus on the prevention of reurbanization of yellow fever through surveillance, vaccination, and control of mosquitoes that spread the disease.

The establishment of a sensitive surveillance system is indispensable for the control and the prevention of yellow fever. Currently notified cases tend to be of the severe clinical form of the disease and, consequently, they correspond to only a fraction of the total number of yellow fever virus infections, since as many as 50 percent of the cases can show no symptoms.

High levels of vaccination are required to protect individuals that live in areas where the disease is prevalent and those who live in nearby urban areas infested with Aedes aegypti.

"Definitively, the best way to guarantee that urban yellow fever does not return to the cities is to reduce the density of Aedes aegypti and to increase the numbers of people vaccinated in the high-risk areas. At the same time, we have to have a good vaccination program for tourists and travelers, who move between countries and from zones where there is risk of yellow fever to zones without risk, and vice versa," said Dr. Arias.

Health Ministers at the PAHO Directing Council called on Member States to include vaccines against yellow fever in national immunization programs in all areas at risk of transmission of the disease.

The countries and territories that have included universal immunization of children against yellow fever are Trinidad and Tobago, Guyana, and French Guiana. Brazil, Ecuador, and Peru have given priority to immunization of children in enzootic areas. Trinidad and Tobago and Guyana have carried out "catch-up" vaccination campaigns in all age groups in the entire country. Brazil and Ecuador have used the same strategy for enzootic areas and regions with high risk of transmission of the disease. Peru, Bolivia, Suriname, and Venezuela have prepared plans to introduce the vaccine against yellow fever into their vaccination schedule for children, as well as vaccination of all age groups in the enzootic areas.

Current strategies for control of the urban yellow fever vector Aedes aegypti are based mainly on the reduction of breeding sites through elimination of standing water, covering water containers, and discarding old tires and other sources of breeding sites. Social communication, community participation, and health education are all being used as fundamental elements in control strategies. Insecticides are used widely where there are high population densities of vectors.

Dr. Arias explained that PAHO is supporting the countries in programs to reduce vectors and to increase vaccination of people in high-risk areas. It is also helping countries to acquire vaccine at reduced cost, and cooperating with laboratories in new technologies in vaccine production for the countries of the region.

"There is a great interest in keeping urban yellow fever out of the region. The countries are clearly cooperating, improving their surveillance systems and reporting cases promptly. The principal challenge of our program for the coming years is to execute the strategies that we have proposed with the speed necessary for maintaining the region free of urban yellow fever," Dr. Arias said.

PAHO, which also serves as the Regional Office for the Americas of the World Health Organization, was established officially in 1902 and is the oldest health organization in the world. It works with all the countries of the Americas to improve the health and raise the living standards of their peoples.