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Revista MVZ Córdoba

Print version ISSN 0122-0268

Rev.MVZ Cordoba vol.22 no.2 Córdoba May/Aug. 2017 


Neglect and not forgetting produces shameful diseases such as yellow fever

La negligencia y no el olvido, produce enfermedades vergonzosas como la fiebre amarilla

Marco González T1 

Salim Mattar V2 

1 Editor Revista MVZ Córdoba, Colombia

2 Coeditor Revista MVZ Córdoba, Colombia

Yellow fever (YF) is a disease caused by a flavivirus that bears its name, is a disease with haemorrhagic manifestations and high lethality that compromises the central nervous system. YF has two cycles; one in the jungle and another urban, epizootics precede outbreaks before migrating to urban areas. The vectors are the mosquitoes Aedes aegypti, Aedes albopictus, Haemogogus janthinomys and Sabethes sp, which have a wide geographical distribution in Colombia and South America.

In 1873 the physician J.M. Toner, who was President of the US Medical Society, wrote the article entitled “Reports upon yellow fever. The distribution and natural history of yellow fever has occurred at different times in the United States”. In that work, Toner incorporated meticulously and with excellent cartography masterly described on a map of the city of Memphis (Tennessee) the cases of YF and related them with the variables of altitude, humidity and temperature. In some parts of the article he wrote: “The humidity in the atmosphere is relative to the season, and as is as is well known, the absolute humidity is greater in the summer than in the winter, warm air having a greater capacity to contain moisture than cold air”… and in another paragraph explained: “we shall in this paper studiously avoid discussing the questions whether yellow fever is a specific disease or not; whether it is always imported; or whether under certain conditions it may originate within our own country”…” that is, he mentioned for the first time in the history of infectious diseases the concept of emerging diseases although he was not sure of the etiology of YF. However, he accurately described the YF epidemic on the Mississippi River between 1693 and 1878.

The old YF, known as Toner’s story, has been important in South America and Brazil, Peru, Bolivia, Colombia and Venezuela are the countries with the highest incidence of YF since 1985. In Colombia between 1916 and 1940, the oil industry in the city of Barrancabermeja, apparently suffered the disease and many workers died (1). Between 1985 and 2000, there were 12 cases, 21 between 2001-2002 and in 2003 the strongest outbreak in history with 101 cases, which began in the population of Tibú, department of Norte de Santander; The lethality was 42%. The outbreak included epizootics in the departments of Cesar, Magdalena and Guajira, monkeys Alouatta seniculus rufiventris died as a result of the action of the virus (2).

Recently in Brazil between December 1, 2016 and February 22, 2017, 1336 cases of YF infection have been detected (292 confirmed, 920 suspects and 124 discarded), including 215 deaths (101 confirmed, 109 suspected and 5 discarded). The most affected states were Bahia, Espírito Santo, Minas Gerais, Rio Grande do Norte, São Paulo and Tocantins. The estimated case fatality rate is 35% for confirmed cases. To date, 86% of confirmed cases are men, of whom approximately 81% are between 21 and 60 years old. As of 22 February 2017, 883 epizootics of non-human primates have been reported, of which 337 have been confirmed by laboratory or epidemiological link. Epizootics have been reported in the Federal District and in Alagoas, Bahia, Goiás, Espírito Santo, Mato Grosso do Sul, Minas Gerais, Paraná, Pernambuco, Rio Grande do Norte, Rio Grande do Sul, Santa Catarina, São Paulo, Sergipe and Tocantins (3).

The abrupt circulation of YF again in Brazil demonstrates how difficult it is to control the infection in wild tropical areas close to human conglomerates, and although Brazil has made enormous efforts to vaccinate the population at risk, some human deaths could not be avoided. In addition, howler monkeys are dying in masse and it is believed that between 80% and 90% of their population died in Espírito Santo and Minas Gerais, the two states most affected so far (4).

In addition, affected states such as Minas Gerais had had epizootics of YF. It is important to ask, Why were human populations not vaccinated in areas prone to infection? The question arises because the Alouatta howler monkeys are the first to die in the jungle areas. Why was the mortality of these monkeys in natural sentinels not detected?. Similarly in Colombia in 2003, despite the fact that the indigenous people of the Sierra Nevada de Santa Marta alerted health authorities about the mortality of primates, cases and deaths occurred; at that time Colombia shamefully had no vaccines available.

Although Colombia has immediately taken vaccination measures at the borders, given the proximity to Brazil, the threat persists in vulnerable populations such as indigenous people and farmers who live in jungle areas. However, there are populations of A. seniculus in the departments of Antioquia, Meta and Casanare. The ecological models also showed that the departments of Antioquia, Bolívar, Guajira, Magdalena, Meta, Santander, Norte de Santander and Vichada have areas with probability of transmission (5). Therefore, a dynamic vaccination should be carried out in at-risk human populations.

In a recent publication in August 2016, Shearer et al (6) conducted a retrospective analysis, collected data from various sources (WHO and Health Services) on FMD vaccination activities between 1 May 1939 and October 29, 2016. Given the uncertainty of how vaccination campaigns were targeted, three population coverage values were calculated to cover alternative scenarios. They combined this data with demographic information and continued vaccination coverage over time to estimate the proportion of the population that had ever received an YF vaccine from each area (states) in countries at risk of transmission of the virus. The YF from 1970 to 2016.

The study established that there have been substantial increases in vaccine coverage since 1970, but there are still significant gaps in current coverage within YF risk areas. They estimated that between 393.7 million and 472.9 million people still need to be vaccinated in areas at risk of YF transmission to reach the 80% population coverage threshold recommended by WHO. This represents between 43% and 52% of the population within the risk areas of YF, compared to 66% and 76% of the population that needed vaccination in 1970. The results highlight important gaps in the coverage of YF vaccination. With the exception of Bolivia, Peru and Senegal, coverage is less than 80%. In Colombia, in the age groups from 0 to19 years, a vaccination of 80% was achieved, however, between 20-70 years only reached 10%. The risk maps of Colombia between 1970 and 2016 show a decrease in the proportion of the vaccinated population.

YF can not be eliminated due to the presence of wild non-human reservoirs which they maintain in the jungle cycle of the transmission. However, South American countries must implement aggressive vaccination programs in areas where epizootics have historically existed, thereby avoiding virus activity from jungle areas to cities. Neglect in vaccination programs is a disgrace in any public health system. In addition, an ecoepidemiological surveillance should be carried out to include the areas where the Alouatta monkeys live and, in this way, to register if they become ill in the forest, this alert is very effective. However, we believe that the strength in the public health’s programs is to vaccinate vulnerable populations living in rural areas with high vectorial activity and circulation of the YF virus.


1. Luna-García JE. La salud de los trabajadores y la Tropical Oil Company. Barrancabermeja, 1916-1940. Rev Salud Pública 2010; 12:144-156. [ Links ]

2. Velandia MP. La re-emergencia de la fiebre amarilla en Colombia, 2003. Rev MVZ Córdoba 2004; 9(2):459-462. [ Links ]

3. WHO, Yellow fever - Brazil [on line]. World Health Organization 2017. URL available in: [ Links ]

4. Universitam. Epidemia de fiebre amarilla ha diezmado a los monos de Brasil y está matando a humanos [en linea]. Universitam 2017. URL Disponible en: [ Links ]

5. Piedrahita-Cortés J, Soler-Tovar D. Distribución geográfica del mono aullador rojo (Alouatta seniculus) y la fiebre amarilla en Colombia. Biomédica 2016; 36(Supl.2):116-124. [ Links ]

6. Shearer FM, Moyes CL, Pigott DM, Brady OJ, Marinho F, Deshpande A. Global yellow fever vaccination coverage from 1970 to 2016: an adjusted retrospective analysis. Lancet Infect Dis 2017; [ Links ]

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