On Friday the CDC issued travel advisories for pregnant women in the areas of Latin American and Caribbean region currently affected by zika virus infection. In the Caribbean currently zika is found only in Haiti, Martinique, and Puerto Rico, but I believe this situation could quickly escalate and expand. My rationale is this is more or less what we saw with another arbovirus infection transmitted by Aedes mosquitoes known as chikungunya. In the New World chikungunya first appeared on the Caribbean island of Saint Martin in December of 2013, but by the following year the virus had spread throughout the Caribbean and Latin America, such that currently the virus is found in 45 countries in the Americas. If zika uses the same playbook we can expect it to become widespread in the Caribbean over the coming weeks and months.
Accordingly, it will be important for women who are pregnant or planning on becoming pregnant to consider the potential implications of travel to the region. Thus although the CDC travel advisories focus mostly on areas known to be infected by zika we must recognize that this is very a rapidly moving target.
I’m especially worried about Haiti, where I believe the areas worst human tragedy could emerge. According to their ministry of public health, zika has arrived in Haiti with five known cases in Port-Au-Prince, the capital. The reason I am specifically concerned about Haiti is because of its extreme level of poverty, together with findings published in PLOS Neglected Tropical Diseases that arboviruses (viruses transmitted by mosquitoes) disproportionately affect poor people. The links between poverty and neglected tropical diseases such as arboviruses need to be better studied but there are some plausible explanations for the association. They mostly include factors that increase contact between humans and mosquitoes such as poor quality housing without window screens or air conditioners and outside degradations of the environment (including piling up of refuse or discarded tires) that allow mosquitoes to proliferate. According to UNICEF there were 264,500 babies born in Haiti in 2012, which roughly translates to a quarter of a million pregnancies annually – I believe that we now need to consider all of these pregnancies at risk for maternal zika virus infection and the potential for a large birth cohort of microcephaly cases later this year or beginning next year. That is of course unless we can begin intervening now with enhanced surveillance and vector control programs.
Outside of Latin America and the Caribbean, the first imported case of zika into Hawaii was just reported, as was the first case in Texas in the Houston-Harris County area. My concerns are not so much these imported cases but instead the fact that both Hawaii and Texas (as well as several other Gulf Coast states) host two species of mosquitoes capable of transmitting zika virus – Aedes aegypti and Aedes albopictus. Widespread poverty in Texas and the Gulf Coast could further fuel the emergence of zika virus infection. As we move into the warmer spring and summer months, we will need to actively look for evidence of zika transmission in the US by catching and examining mosquitoes for the virus, as well as sampling the blood of adult patients who exhibit signs and symptoms consistent with Zika, such as fever, headache, and rash. If zika gains a foothold in the US it will require aggressive public health control activities aimed at eliminating mosquito breeding sights while ensuring that accurate and timely information is provided to women of reproductive age.
I’m afraid it looks as though the winter and spring of 2016 is going to be an interesting and anxious time.
-by Peter Hotez M.D. Ph.D., Dean of the National School of Tropical Medicine, Texas Children’s Hospital Endowed Chair in Tropical Pediatrics, and president of the Sabin Vaccine Institute. He is also university professor at Baylor University and Baker Institute Fellow in Disease and Poverty at Rice University.