hi your nephew got fever on and off so most probably it may be
*Arthropod borne disease (dengue
, Chikungunya, Japanese encephalitis
, marbug &ebola)
In your question there is no history suggestive of mosquito bite i rule out malaria;
no history suggestive of intake of contaminated food and water so i rule out typhoid in which rose spots appear only on trunk so i rule out typhoid; regarding marbug & ebola is of geographical distribution and its significance.
so last option is dengue were feer is biphasic(saddle back fever) and rashes last for 2 hoursto seeral days followd by desquamation ; check for NSA1Ag, Igm Ab. IgG Ab mostly it is supportive and symptomatic if platlet is soo less advice platlet infusion