**Core Concept**
The case presents with symptoms of a severe systemic reaction, likely due to an **envenoming** or **toxic** exposure. The child's symptoms, such as sweating, vomiting, cold hands, tachycardia, and hypotension, suggest a **sympathetic nervous system** overload or a severe **infectious** or **toxic** process.

**Why the Correct Answer is Right**
Given the scenario of a child sleeping in a thatched hut and waking up with severe systemic symptoms, it is plausible that the child was exposed to a venomous creature, such as a snake or a scorpion, which are commonly found in such environments. The symptoms of sweating, vomiting, cold extremities, tachycardia, and hypotension are consistent with **scorpion stings**, which can cause a massive release of **catecholamines** leading to a **sympathetic storm**.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the symptoms do not specifically point towards a common infectious disease that would present with such acute and severe systemic symptoms without other localizing signs.
**Option B:** Without more specific information, it's hard to rule out other causes, but the presentation doesn't strongly suggest this as the primary diagnosis.
**Option C:** This option might seem plausible but doesn't fit as well with the acute onset and specific combination of symptoms described.

**Clinical Pearl / High-Yield Fact**
In cases of suspected scorpion stings, especially in endemic areas, it's crucial to monitor for signs of cardiac and respiratory compromise, as these can be life-threatening. The use of **prazosin** has been advocated in some cases to manage the hypertensive crisis associated with scorpion stings.

**Correct Answer:** D. Scorpion sting.