Zika Virus, 2016

Zika virus is a mosquito-borne flavivirus that was first discovered in 1947 in Uganda, and the first human cases were identified in 1952. Historically this virus occurred only sporadically in Africa and Asia, but it gained attention after it resulted in outbreaks in Micronesia in 2007 and French Polynesia in 2013-2014. In Spring 2015, cases were reported from Brazil, representing the first time the virus had been found in the Americas. Since then, the virus has spread to nearly 50 countries and territories in the Western Hemisphere, and infections during pregnancy have been associated with adverse fetal outcomes, including microcephaly. Zika has been shown to be transmitted perinatally as well as through sexual contact, a route of transmission that has never before been associated with a mosquito-borne virus. The mosquito vectors for humans are the same Aedes spp. mosquitoes (Ae. aegypti and Ae. albopictus) that transmit dengue virus and Chikungunya virus.

Most people (up to 80%) infected with Zika virus do not develop symptoms, and of those that do, most will develop mild symptoms like fever, rash, joint pain, and conjunctivitis. Symptoms usually begin 3-7 days after a person is bitten by an infected mosquito, and most recover within a week. In some cases, severe complications such as Guillain- Barré syndrome can occur in patients following infection. With such a high proportion of asymptomatic infections, it is possible that many infections go undetected.

In 2016, 73 cases of Zika virus disease were reported in Minnesota residents. The median case age was 37 years (range, <1 to 82 years). Cases resided throughout Minnesota, although the majority (53 [73%]) were from the metropolitan area, and were reported throughout the year. Ninety-seven percent (71) of cases presented with relatively mild illness, although one individual had Guillain-Barré syndrome, and one was a probable congenital infection. Six women were found to have laboratory evidence of Zika virus infection during pregnancy, and to date, none of these infections have been associated with adverse pregnancy outcomes. All but 1 of the cases represented imported infections acquired abroad. This domestic case was due to sexual transmission from a symptomatic male to his female partner. For those cases associated with travel, patients reported travel to 24 different countries and territories in the Americas, with Haiti (13), Mexico (11), Nicaragua (7), Guatemala (4), and Jamaica (4) being the most common.

Nationwide, human cases of Zika virus disease were reported from 49 states and the U.S. territories of Puerto Rico, American Samoa, and the U.S. Virgin Islands. Most U.S. cases were acquired while traveling abroad, although local transmission was identified in Miami, Florida and Brownsville, Texas, resulting in 224 locally acquired cases (218 from Florida and 6 from Texas).

• For up to date information see>> Zika Virus
• Full issue>> Annual Summary of Communicable Diseases Reported to the Minnesota Department of Health, 2016