Zika virus: Should I be concerned?

Zika virus is suspected to be the cause of an epidemic of newborns with small heads (microcephaly) and delayed development in Brazil. In 2014, the country had just under 200 babies born with this serious and lifelong condition and in 2015 there were almost 3,000 cases. Several hard-hit areas have declared states of emergency about it.

The mother became ill with the Zika virus while living in Brazil in May 2015 and the baby was likely infected in the womb, according to Hawaiian state health officials and the Centers for Disease Control and Prevention.

Last week, it was also diagnosed in a traveler in Houston. The virus isn't poised to spread in the U.S., but some experts are worried about it. Last Friday, U.S. health officials issued a travel warning for 14 countries and territories in the Caribbean and Latin America where infection with Zika is a risk. The travel alert includes Brazil, Colombia, El Salvador, French Guiana, Guatemala, Haiti, Honduras, Martinique, Mexico, Panama, Paraguay, Suriname, Venezuela and Puerto Rico. The CDC cautions pregnant women not to travel to areas where the virus is present.

Why is the spread of Zika virus occurring now? Probably two ecological changes are responsible.

The world is smaller than it used to be. During a leisurely week long cruise in the Adriatic Sea last year, I visited Venice, five walled cities in Croatia, Montenegro, Albania, and Greece.  Unfortunately, if I had caught a viral illness in Venice, I could have spread it to people in four other countries. If you add in air travel, diseases can move very quickly. In 2015, a single case of measles that was brought to Disneyland spread through at least 113 people in over 20 states. The traveler was probably exposed in the Philippines since the serotype was identical to one that caused an epidemic in that country in 2014.

The world is also warmer than it used to be, quite a bit warmer this last year. This warming made a mosquito called Aedes aegypti very happy. This disease vector (which carries germs that cause disease) spreads yellow fever, malaria, many other diseases, and a previously little known germ called Zika virus. A. aegypti loves wet (especially standing water) and warm conditions.  The most effective insecticide against it, DDT, cannot be used because it has made too many other species ill including humans and birds of prey.

Zika causes fever, rash, headache, muscle and joint pain. The virus (distantly related to yellow fever) was first isolated over 50 years ago in a swampy area of Uganda and first noted to cause human disease in Nigeria 20 years later. But its spread through a wetter, warmer Brazil has coincided with this horrible epidemic in newborns.  Although it is not common enough elsewhere in the New World to cause much disease yet, Zika has been detected all over the Americas this last few years with germs found as far north as Mexico. It has spread with other viruses carried by the same mosquito such as chikungunya virus (which causes bone pains along with fever and rash).

We believe that when a mother catches Zika virus in the first three months of a pregnancy, it can prevent the fetus's brain cells from developing normally and if the brain cells do not grow, the head does not grow.  Many other germs can cause fetal brain damage such as toxoplasmosis or herpesvirus, but many mothers have resistance to these infections, almost no one in the New World has resistance to Zika virus yet.

Climate change is causing infection problems along with heat waves, increased storms, drought and flooding.  We need to find ways to improve the odds that humans will win the fight against the mosquito for control of where we live. If you're considering traveling abroad, it's important to check with the CDC for any travel warnings.

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