There are good, although small rural hospitals in Tonosí and in Pedasí, both of which are a 30 minute drive from Eco Venao. Both towns also have pharmacies stocked with most basic medicines. There have been no cases of Malaria or Dengue Fever in the immediate area. This is largely due to the absence of mosquitos. Thankfully, they are only occasional visitors here. Noseeums known locally as Chitras (sandflies) can be a nuisance during sunrise and sunset. Herbal repellants may be helpful to bring with you.
In recent years there have been a handful of cases of the rodent borne Hantavirus in the region. While travelling, or on your return, it is always advisable to seek medical advice for any high fever or other flu like symptoms.