I requested a mosquito net at the Dreamcatcher's Hotel so I could leave the doors open rather than ... [+] use air conditioning. They were very accommodating.

Most sites offering travel safety advice focus on petty theft, watching that your drinks aren’t spiked, and being careful after dark. Little is written about reducing your infectious risk beyond “Don’t drink the water or ice.”

Being an infectious disease doctor, I wanted to share my concerns about travel to the Caribbean now and how you might have a safe(r) trip.

I’m in Puerto Rico now, my first major travel since Covid began. It’s been good for my soul, and while I’m likely taking more precautions than many would—an occupational hazard mostly from seeing complications of things—I’ve felt safer here than most places at home.

Frankly, my flight on United Airlines was the scariest part of the trip. I’m sure they are not unique in having lousy ventilation. I watched my Aranet 4 CO2 monitor readings throughout the flight. They rose to 2900 during boarding and were never less than ~1700 during the flight.

Dr. Jeff Gilchrist had a helpful thread about CO2 levels, and offered a “spreadsheet shared air calculator. When the CO2 levels are at 975 ppm, you can see that every breath people take in that room contains 1.5% of the collective breath of others. This may not sound like much, except the typical amount of air inhaled per day means you are breathing in 6 litres every hour of other people's breath. If ventilation was horrible and CO2 levels were 3152 ppm, that would be 30 litres every hour of other people's breath.”

We wore N-100 masks and did not remove them for a moment, except for TSA’s identification check, from the time we boarded a shuttle bus at Dulles until we were in our auto rental. It was uncomfortable, but thankfully, we did not get Covid. Hardly anyone was masked on our flight. The flight attendant falsely thought that vaccines protected him entirely from infection. Then again, he thought Puerto Rico was a foreign country.

Regarding Covid, Puerto Rico is a good destination. Per CovidActNow.org, in Puerto Rico, “(95.0%) have received at least one dose, 2,767,570 (86.7%) have received at least two doses or a single Johnson & Johnson dose, and 1,756,532 (55.0%) have received a booster shot.” In my home county, 64% have received at least one dose, 57% two doses, and only 31% a booster.

Far more people mask in stores in Puerto Rico, too—I’d estimate perhaps a third do, while masks in my town are a rarity. One can also readily find an outdoor restaurant here, making eating out much safer.

While I’m told that the water here meets the same standards as on the mainland, I was concerned because of the recent hurricanes and damage to the infrastructure. We have used a manual water purifier/filter we brought and bought bottled water, something I am generally loathe to do.

Other standard advice for traveling where hygiene may be a problem (as from the recent hurricanes) is avoiding fresh fruits and vegetables unless you can peel them. Surprisingly, bananas were unavailable in San Juan for more than a week due to Hurricane Fiona destroying the crop. We stayed in hotels or rentals with kitchen facilities, which made life considerably easier and more pleasant. We made our ice and bought citrus that could be peeled and frozen berries.

Diarrheal diseases are the most common travel-related illness. They are acquired from eating contaminated food or water. Pepto-Bismol prophylaxis might be something to consider, or taking it at the first sign of diarrhea.

In general, if you will be traveling to countries in the “Global South,” being up to date on vaccinations is wise. This would include Hepatitis A, a highly infectious virus transmitted through water or food contaminated with stool.

A tetanus booster is a reasonable precaution and getting the TDap, which also protects against pertussis (whooping cough), might help curtail its spread.

You should be aware of a few zoonoses, or infections transmitted from animals, if planning a vacation now.

One is leptospirosis. This is a bacterial infection acquired from water contaminated by animal pee, especially from rodents. There have been 108 suspected, probable, or confirmed cases in Puerto Rico just since September of this year, when Fiona hit the island. There have been 14 deaths during this same period. Leptospirosis has been associated with white water rafting, kayaking, or other water sports and with wading or swimming in contaminated water. That’s why, as tempting as this swimming hole was, I didn’t jump in.

Swimming hole in El Yunque rain forest, Puerto Rico

Many leptospirosis infections are mild and likely to be missed, so the numbers of infections are likely much higher. Symptoms are non-specific flu-like illness and conjunctivitis (red eyes). More severe cases include liver involvement with jaundice, meningitis, and death. Treatment is with doxycycline.

While schistosomiasis is most common in Africa, this parasite is also found in the Caribbean islands and Brazil. It is transmitted in freshwater by the larvae penetrating the skin while people are swimming, wading, or bathing. Acutely, people can develop a rash and respiratory symptoms. The infection can be quiet and not appear for years, presenting later with blood in stool or urine. Being rarely seen in the US, diagnosing and treating it would likely be difficult. It’s so important that you tell your physician about travel and unusual exposures—that’s often critically important in making a diagnosis!

Hookworm can also be acquired by walking barefoot, so please wear water sandals or the like.

Be careful to clean cuts sustained in salt water thoroughly to help prevent Vibrio vulnificus infections. The skin may develop bloody blisters—a major warning sign—and shock can develop.

Malaria is, thankfully, only endemic in Haiti and the Dominican Republic.

Chikungunya, a viral infection transmitted by mosquitoes is found in Latin America but not on the islands.

Unfortunately, there are still occasional Zika cases on the islands, particularly in Puerto Rico. [Addendum: 12/21/22 5 pm: There is conflicting information presented re the risk of Zika. CDC here says there are no cases since 2019. But here: “Women living in Puerto Rico are at risk of Zika virus exposure due to local mosquito-borne transmission of Zika virus." Finally, “the Puerto Rico Department of Health Weekly Arboviral Diseases report indicates the Zika virus continues to infect people in 2022. The Report published on Feb. 14, 2022, shows (1) new 'probable' Zika cases confirmed in the San Juan, Puerto Rico vicinity. These Zika cases are in addition to the (101) probable cases reported during 2021, with (10) near the city of San Juan.” A map is provided.]

Dengue is the biggest threat from mosquito bites on the island. This arboviral infection may have a fever as well as headache and body aches, leading to its nickname, breakbone fever. Usually, initial infections are not as serious as repeated infections. Those can be life-threatening with shock and bleeding. The best protection is using a good mosquito repellent with Picaridin or Deet.

While dengue is a significant risk in Puerto Rico (525 locally transmitted cases this year), a larger number of travel-related cases have been reported from Florida (699)!

A sign at El Yunque, the island’s rainforest, warns of rabies among the mongoose. I would be wary of the many stray dogs and cats as well. In one study, 11% of cats tested in Puerto Rico were positive for rabies.

It would be best to consider these significant infections before traveling to the Caribbean. Even while taking precautions, there is plenty to see and do, ensuring you have a great—and safe—vacation.