Updated: Travel and Tourism May Have to Wait.

Correction we used a 0.1% infection rate for daily travel arrivals. A very small number of infected tourists as the potential to seed and outbreak anew. It all depends on the case reproduction rate known as the Rzero.

The Rzero is the rate one person infects others. One or less is ideal, but in some communities it is as high as 3.5. Then 3.5 infect 3.5 and so on.

Masks and social distancing determine the Rzero. What is the Rzero on a large jet plane, a hotel lobby, or a tourist bus if the tourists fail to wear a good mask and distance themselves?

The chart has three iterations of a simple model. Here is how the model works. On day 1 8000 people arrive, 8 are infected but do not know it, so they don't isolate. Those 8 cause 20 new infections by 96 hours after arrival. At seven days 50 more become infected. This happens now each day as 8000 more arrive. The geometric growth in cases is explosive for the Rzero of 2.5. The infected persons will overrun a small tourist community hospital in two weeks.

In contrast, if the tourists are very respectful and employ all infection controls and the Rzero is reduced to 1.1, the number of new cases is only 271. If good testing, tracing and isolation is put into effect the impact of the disease on the community will be manageable.

The rights of the community to protect the common welfare is theirs and theirs alone, inarguably.

The weak link.....Even in persons with profound COVID 19 disease can test negative for the virus RNA. In non diseased or pre-symptom infections, some 67% will test false negative. Bottom line, requiring a negative test 72 hours before travel will miss many infections. More than likely more than 0.1%. It is prudent to limit travel based on sound data.