The current situation
In 2001, WHO launched a major initiative to reinforce disease control and surveillance.
During the last ten years, the number of new cases of HAT reported to WHO has shown a clear decrease, either in the Gambiense form as well as in the Rhodesiense form. For the first time in more than 50 years, the number of reported cases dropped below 10,000 cases per year: 9878 new cases were reported in 2009 and 7139 in 2010. The decrease of cases reported during the period 2001-2010 has been 73,4%. This reduction does not reflect a lack of control efforts as active testing has been maintained between 3 million and 2 million and a half people screened by year and the number of health centres and hospitals participating in the passive screening has increased.
It is obvious that underreporting is not negligible as the disease that is not easy to diagnose and occurs in rural, remote and sometimes unsafe areas where health systems are weak. Nevertheless, the epidemiological data and the increased coverage of control and surveillance programmes, allows to consider that the fraction of cases not reported is decreasing.
But the current epidemiological scenario of HAT is not homogeneous. 4 different contexts could be defined:
- West Africa: Very low prevalence situation.
Some historical disease endemic countries not referring cases in more than 10 years (Benin, Burkina Faso, Ghana. Mali, Togo) despite control activities are going on. Some other countries (Guinea Bissau, Gambia, Senegal, Niger and Sierra Leone) do not declare cases. Although control activities are not running regularly rough assessment has been done and it seems that cases of HAT are not present. In Liberia the situation is similar but better assessment of the state is needed. A different situation is faced in Guinea, Cote d'Ivoire and Nigeria were transmission is still active but prevalence is low and limited to well defined foci. On top of that security situation in affected areas of Nigeria is worrying and could hide an alarming situation.
- Central Africa: Active transmission with low or very low prevalence.
Foci are well known and well limited, with a very low (Cameroon, Equatorial Guinea, Gabon):or low prevalence (Angola, Central African Republic, Chad, Congo, South Sudan North West Uganda), and in general with a decreasing trend. Control and surveillance activities are on going. Just to remark the unstable security situation in the foci of CAR and South of Sudan. During the process of independence in South of Sudan surveillance of HAT has decline and the transmission could have been increased. More attention must be devoted to foci in this country.
- Democratic Republic of the Congo: It means the most important burden of disease (>80% of total HAT cases).
The internal situation is not homogeneous with regions with high prevalence (Bandundu, East Kasai, Oriental Province and some areas in Equateur) and areas with low prevalence (Bas Congo, Kinshasa, Equateur). Some areas need better assessment of the situation (Sankuru, Nord of Bandundu, areas of Equateur, Orientale Province and Maniema).
- East Africa:
The number of cases is low (less than 200 cases notified / year, > 3 % of total HAT cases reported) but not negligible its risk of going to epidemics.
The epidemiology of the disease is different and it should be considered as a zoonotic disease. We can distinguish two areas, one with disease mainly related to cattle (Uganda, Kenya) and another with disease related to game and wild animals (Tanzania, Malawi, Zimbabwe, Zambia). Cases have not been reported in Botswana, Burundi, Ethiopia, Mozambique, Namibia, Rwanda and Swaziland for more than 15 years.
For an epidemiological update, see:
Weekly Epidemiological Record, 2006, 81:69-80
Report of a WHO informal consultation on sustainable control of human Afican Trypanososmiasis, Geneva, 1-3 May 2007 | and French
Eliminating Human African Trypanosomiasis: Where do we stand and what comes next? By P. Simarro, J. Jannin, P. Cattand – PLoS Medecine, Feb. 2008.
The human African trypanosomiasis control and surveillance programme of the World Health Organization 2000-2009. The way forward. By P. Simarro, A. Diarra, J.A. Postigo, J.R. Franco and J. Jannin – PLoS NTD, Feb. 2011.