Our team is on highest alert now, after monitoring the progress of Chikungunya (CHIK) reporting in Saint Martin, which went from two reported cases to now 10. This implies transmission has occurred and was sustained as opposed to limited autochthonous transmission. Now we are watching closely because if St Martin loses control of the situation and the disease spreads, we may see a repeat of what we saw in Reunion and southern Asia: explosive spread in the region with implication for the Caribbean, Central and South America, and the United States.
CHIK spreads by way of the same vector as dengue, Aedes aegypti. CHIK also clinically mimics dengue, except CHIK does not cause mortality but does result in high morbidity. We observed very high attack rates among communities experiencing "first contact" with what to them was an exotic pathogen, which meant large numbers of patients presenting incapacitated with fever and joint pain.
During its rapid, explosive spread across southern Asia, we observed IDIS Cat 4 and 5 (i.e. near-maximal) levels of social disruption due to public perception they were dealing with an extreme year of dengue. Medical infrastructures were inundated with cases, and we observed reports of "panic evacuations" of villages. This virus, when introduced to nascent tropical environments can transmit explosively, and as southern Asia found out.
The distribution of Aedes aegypti effectively covers the southern US, the Caribbean, Mexico, Central and South America. What is at stake now, if St Martin and PAHO fails to eradicate CHIK, is effectively half the western hemisphere. Puerto Rico should be on high alert and conducting active surveillance. We are concerned about introduction to Haiti.
Why is this different than expansion through southern Asia? Indeed, there was translocation risk to the US at that time by air flight, and we did see multiple cases introduced to the US. And, we have indication this phenomenon was underreported. However, the thought of establishment of this virus in Mexico, Central America, and South America presents a whole different risk of subsequent establishment in the US thanks to the tremendous flow of human beings across our terrestrial borders. All of the border states will be placed at risk. All states receiving migrant labor will be placed at risk.
It should be said that this issue worries us more than the recent translocation of Nepalese / Haitian cholera to Mexico.