@Arnold68 It's only just geting into tourist season, so nothing really to report yet. They have cleaned up the sewage treatment plant- it no longer runs right into the ocean. A lot of what people attribute to health issues here are really just as result of so many tourists coming here- lots of them are sick when they come, though they may not have had any symptoms yet. They're quick to blame it on Sayulita, but that's not always the reality. Things like Norovirus go around, but those things go around all over the world. When you have wedding parties of 50 people coming down in January, the chances that some of them are going to be carrying some sort of common winter flu virus isn't hard to imagine. Then if 15 of those people have booked a house together, they're going to be exposed to more germs than they would be if they stayed in their own home. And of course, bacteria and viruses thrive more easily in a tropical climate.
Also people's lifestyle when they're on vacation here can facilitate getting sick- they drink too much, stay up later than they normally would, get sunburned, neglect to drink enough water. Those things can lower the immune system.
I live here- I never get sick. So that should tell you something. People should take the same precutions they would anywhere outside their own home- wash hands frequently, carry anti-bacterial wipes, eat foods that are cooked, or buy groceries and cook for yourself, peel fruit before eating, soak salad veggies if you're eating in, in the antibacterial soak they sell here, brush your teeth with bottled water, etc. If I eat out, I like to eat places that I know are clean, or where I can actually see the kitchen area. And I've ever gotten sick on street tacos.
One good thing to carry with you when traveling is charcoal pills- I actually keep them on hand for guests. Some of my guests have come equipped with them. One in the morning and one at night as a preventative measure can keep you healthy, at least as far as stomach problems.