Background: Nigeria is the most populous black nation with the heaviest burden of Sickle Cell Anaemia divided into a cold and dusty harmattan season and a hot non-harmattan dry season. We studied the impact of seasonal variations of climatic factors on the frequencies of acute vaso-occlusive morbidities, including Vaso-Occlusive Crisis (VOC), Acute Chest Syndrome (ACS), priapism and stroke among patients with SCA in northern Nigeria.

Methods: This is a six-year prospective study conducted from 2005 to 2010 in university teaching hospitals of Maiduguri and Kano cities of northern Nigeria. Consecutive patients with SCA who presented with VOC, ACS, priapism and stroke were diagnosed, recruited and enumerated. The monthly and seasonal frequencies of each morbidity (VOC, ACS, priapism or stroke) during the period of study were calculated and graphically evaluated.

Results: The frequencies of VOC showed 3 peaks: during the harmattan dry season in January, during the non-harmattan dry season in April and during the rainy season in August. The frequencies of ACS showed a peak during the harmattan dry season in December. The frequencies of priapism showed a peak during the nonharmattan dry season in April. The frequencies of stroke showed a peak during the rainy season in July/August.

Conclusion: The frequencies of acute vaso-occlusive morbidities in SCA patients could be adversely affected by seasonal variations in climatic factors. There is need for patients and care givers to be adequately educated on how to mitigate the adverse effects of weather on SCA. Moreover, governmental and non-governmental organizations should take seasonal variations of climatic factors into consideration when drafting health care plan for patients with SCA. is dominated by the trans-Atlantic tropical maritime air mass, which brings about rainfall as well as dense cloud cover that blocks sun rays resulting in relatively modest average temperatures of between 29 C to 21 C at the peak of the rainy season in August [3, 5]. hereafter, the dry season sets in during the period October to February when the region comes under the influence of dry and dusty trans-Saharan tropical continental air mass, which is referred to as the Harmattan [2, 3]. he harmattan is associated with low atmospheric humidity, increased wind speeds and dusty haze, which partially blocks the sun rays over northern Nigeria with a resultant fall in average temperatures to as low as 13 C with many daily temperature values reaching as low as 3 C especially in the evenings and night times [2, 3, 5]. he harmattan recedes upon the withdrawal of the tropical continental air mass during the period March to May (non-harmattan dry season), which is characterized by the absence of both haze and cloud in the skies, hence average temperatures escalate to as high as 38 C with many daily temperature values exceeding 40 C [2, 3, 5]. he temperatures remain