Learn Spanish (Latin America): El brote se propaga debido a la higiene inadecuada. - The outbreak spreads due to inadequate hygiene.

We use debido a because it is directly followed by a noun phrase (la higiene inadecuada). You only use debido a que when you are introducing a clause with a conjugated verb, such as debido a que la higiene es inadecuada.

Since this is a negative situation, could we use por culpa de instead of debido a?

Yes. While debido a and a causa de are neutral ways to express cause, using por culpa de is very natural here because an outbreak is clearly a negative event. However, you would not use gracias a, because that connector is reserved for positive outcomes.

Why is there a se before propaga?

The verb propagarse is used here to show that the action happens on its own, without a specific external agent doing it. While English simply says the outbreak "spreads," Spanish frequently uses se to make verbs intransitive, focusing on the subject undergoing the change.

Why is there a la before higiene when the English translation just says "inadequate hygiene"?

Spanish requires definite articles (el, la, los, las) when talking about general concepts or abstract nouns. Because the sentence refers to hygiene as a general concept, la is required, even though English omits "the" in this context.