Just when you have gotten over the Ebola scare (though you will hear about it again), here comes another viral infection though spread by mosquitoes. Zika virus was first identified in Uganda in 1947 in monkeys and the first verified human infection occurred in 1968. Since then it has smoldered in countries near the equator where 2 strains have evolved, one in Africa and one in Asia. The first infections outside of Africa and Asia occurred in Micronesia in 2007. Since then, the virus has spread throughout the southern Pacific islands and arrived in South America a few years ago. Dense populations of both humans and the vector mosquito has caused Zika to explode in Central and South America. At the time of this article, about 20 cases have been reported in the US, all from people who traveled to areas where the disease is present (such as Brazil).
Zika is spread through bites of Aedes mosquito species, the same vectors for dengue and Chikungunya viral infections. Aedes mosquitoes prefer hot climates but exist throughout many areas of the US. Only about 20% of people infected actually show the symptoms of fever, rash, mild headaches, malaise (weakness), joint pain, and conjunctivitis (inflammation of the lining of the eyes). No deaths have been reported but there is a spike in pregnant women who have been infected delivering babies with abnormally small heads (microcephaly). The long term consequences of infection are unknown, though there is a report of Zika transmission to the female partner of an infected man. This suggests that, like Ebola, the virus may remain in body fluids for some time after recovery. There currently is no vaccination or treatment for Zika.
Part of the problem with recognition of Zika infections is that they share the same symptoms with the more widely prevalent viral infections dengue and Chikungunya which occur in the same general areas. Dengue is an Aedes mosquito-borne viral disease that affects about 400 million people yearly in tropical and subtropical climates. It is endemic (always present) in these areas but epidemics occur periodically. An upsurge of dengue has occurred in the Caribbean and Latin America and it is now reported in Florida and Texas in the United States. There is no vaccination or cure. Though debilitating, there is a low fatality rate (less than 5 percent) if treated. There is a suggestion that longer term effects of dengue may include kidney failure in some patients.
Chikungunya is another Aedes mosquito-borne viral disease, with symptoms similar to dengue and Zika, in Asia, Africa, and the Pacific regions. It recently spread to the Caribbean and Latin America and is now reported in the subtropical United States. The fatality rate from Chikungunya is less than 1 percent. Long term consequences of Chikungunya infection are unknown.
There is no treatment currently available for all 3 of these viral infections. Promising results have been reported for a dengue vaccine and advances in developing a vaccine for Chikungunya are well underway. Zika viral vaccine development has begun.
The best treatment is prevention, so do your best to avoid mosquito bites. Aedes mosquitoes have distinctive stripes and bite during the day with peak activity at dawn and dusk. Use air conditioning, mosquito repellent, nets if camping in tropical or semi-tropical areas, and eliminate standing water because it serves as a breeding ground. Big things come in these small packages!
Michael J. Manyak, MD
VP National Eagle Scout Association
Author, Lizard Bites and Street Riots, Travel Emergencies and Your Health, Safety, and Security