Zika Virus: Another Unwanted Mosquito-Borne Invader

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Dr. David J. Holcombe
Dr. David J. Holcombe

In our days of worldwide travel, germs move with us on our meanderings.  Zika virus has now grabbed the international headlines.  It is a Flavivirus, one of several that is transmitted from human-to-human through the bite of mosquitos.  In this case, as with Dengue and Chikungunya, it is transmitted through the bite of Aedes species mosquitos, present throughout the Southern U.S. and much of the world.

 

Although Zika was previously identified in Southeast Asia and Central Africa, it made the jump to the “New World” recently, probably in 2012 or even earlier.  After arriving by means of an imported infected individual, Zika—like West Nile before it—quickly established itself and now extends throughout much of Central, South America and the Caribbean (notably Haiti and the Dominican Republic).  Although imported cases have been reported in the U.S., Zika has not established itself here yet, and there have not been any reported human-to-human mosquito-borne infections here.  Direct human-to-human transmission might occur through infected sperm, but this appears exceptional.  Much like Dengue and Chikungunya, there is a good chance all three may become endemic to the U.S. given the widespread presence of Aedes mosquitos, a very adaptable species.

 

As far as infections go, Zika virus is only symptomatic in about 20% of those infected, and symptoms are relatively mild (rash, joint and muscle pains, headache and conjunctivitis).  Symptoms last about a week and recovery is the rule.  There is growing evidence, however, that infection in pregnant women can result in cases of microcephaly (babies born with small heads and associated neurological abnormalities).  Pediatricians in Brazil first noticed this association, and several thousand cases have now been reported.  There have also been rare reported cases of Guillain-Barré syndrome, a neurological disorder.

 

Zika virus is difficult to diagnosis and requires specialized blood tests that are only performed at the CDC and a few state health labs (not including Louisiana yet).  The problem is cross-reactivity with other diseases, such as Dengue, which presents with almost identical symptoms.  In fact, the non-specific symptoms of Zika virus resemble a host of other diseases, including Chikungunya, rubella, measles, parovirus, adenovirus and enterovirus.  The clinician must be suspicious of Zika, however, in anyone returning for the many countries where it is now endemic.

 

Like Dengue and Chikungunya, Zika virus has no specific treatment.  Rest, hydrations and acetaminophen are recommended for aches and pains rather than non-steroidal anti-inflammatory medications since these can aggravate bleeding if the disease happens to be hemorrhagic Dengue.  Pregnant women (or potentially pregnant women) should avoid travel in the many affected countries listed on the CDC website.  These travel restrictions may pose a particular challenge given that Rio de Janeiro, Brazil, is the site of the 2016 Summer Olympic Games.

 

As with all mosquito-borne diseases, precautions should be take here and elsewhere to reduce exposure: limit outside activities in the early morning and evening, wear long-sleeve clothing, use DEET or other repellants, repair screens and reduce standing water around homes and businesses. A “simple” mosquito bite, whether in Alexandria or Rio de Janeiro, Brazil, can cause a host of problems.  While locally we still worry about West Nile virus, overseas Zika, Dengue and Chikungunya have established themselves firmly in many countries and are only waiting to invade the continental U.S.