Zika virus in Wisconsin
All confirmed Zika virus cases ever reported in Wisconsin residents are travel-associated, occurring in people who traveled to locations with active Zika virus transmission or in people who had sexual contact with someone who traveled to a location with active Zika virus transmission.
Wisconsin is populated by residents who travel to areas where there is a risk of Zika virus transmission among the local mosquito population, and these individuals can become infected with the virus. Pregnant women are advised not to travel to areas with a current Zika virus outbreak. Both women and men who become infected with Zika virus while traveling can give it to their sexual partners upon their return to Wisconsin, even if they exhibit no symptoms of the virus.
The state's objective is to collaborate on the coordinated response between Department of Health Services (DHS), local public health agencies, health care providers, and other partners in working together to best serve the people of Wisconsin.
DHS Zika Response Partners
Zika virus-related activities within the DHS’ Division of Public Health (DPH) are being coordinated among multiple programs across the division. DHS has been addressing Zika virus since January 2016. DHS is working with several partners across the state including:
- Health care sector
- Health care coalitions
- Local health departments
- Tribal health centers
- Professional associations
- University of Wisconsin-Madison Entomology Department
For more on the Wisconsin Zika Response, see the full DHS Concept of Operations document (PDF)
For more information on Wisconsin's response to Zika virus, the content has been divided into four subject topics.
Zika virus is primarily spread by the Ae. aegypti mosquito, which survives in warmer climates, and has not been found in Wisconsin or any neighboring states. Another mosquito that is capable of transmitting Zika is Ae. albopictus, which has been detected in the Midwest. DHS, in conjunction with the UW Department of Entomology and selected local health departments, has been conducting surveillance for Ae. albopictus using ovitraps to collect mosquito eggs. Surveillance began in July of 2016.
As of 2017, Ae. albopictus has been found in some areas of Wisconsin. This is the first time this species of mosquito has been identified in the state. There is no evidence of Zika-infected mosquitoes in Wisconsin.
The detection of Ae. albopictus in Wisconsin does not change the precautions that DHS recommends for people with a possible exposure to Zika virus. DHS continues to emphasize avoidance of mosquito bites for both returning travelers (so as not to infect a potential vector) and for the public in general. Anyone who may have been exposed to Zika should contact their doctor if they experience fever, rash, joint pain, or red eyes within two weeks of possible exposure, and avoid mosquito bites for at least three weeks after they first become ill or after last possible exposure (if there are no symptoms). Efforts to control mosquito populations and breeding habitats will also be enhanced in locations where the vector has been found.
We do not expect to see indigenous transmission of Zika virus in Wisconsin. However, if a locally acquired case were to occur in Wisconsin, intense efforts would be undertaken to treat the area with insecticides designed to kill adult mosquitoes within about 150 yards of the case’s home, along with elimination and insecticide treatment of habitats favorable to larval mosquitoes.
Surveillance for Zika virus infections is conducted through passive reporting of cases by providers and by laboratories. Zika virus infection is notifiable under Wisconsin Administrative Code. Results from Wisconsin State Lab of Hygiene (WSLH) testing are faxed to epidemiologists within DHS, and are entered into Wisconsin Electronic Disease Surveillance System (WEDSS). Reporting by commercial laboratories varies by the facility.
Potentially infected individuals will typically talk to their health care providers if they think they could be at risk of Zika virus infection. Additionally, pregnant women without symptoms who think they might be at risk of Zika virus infection should talk to their health care providers out of concern for adverse pregnancy outcomes. Center for Disease Control and Prevention (CDC) recommends primary care providers ask all pregnant patients about potential exposure to Zika virus at each prenatal visit.
Recommendations for avoiding mosquito exposure and sexual transmission of Zika virus are given by health care providers and stressed by local health department staff when conducting public health follow-up on patients who have positive results. There is no public health follow-up performed for patients who test negative for Zika virus infection, although additional clinical monitoring and future testing may be suggested.
Two basic types of assays are performed at the Wisconsin State Lab of Hygiene (WSLH):
- a PCR assay that detects the actual RNA of the Zika virus, and
- a serologic test that detects IgM antibody to the virus. Which tests are run depends on when patient specimens are collected in relation to exposure or clinical onset.
Fee-exempt testing is approved on a case-by-case basis by epidemiologists within DHS. Clinic personnel contact DHS by phone and provide exposure information to determine whether the patient meets testing criteria. If criteria are met, an approved submission form and instructions on submission to WSLH are faxed to the clinic. The WSLH performs testing at least weekly, so the turnaround time for results typically does not exceed seven days.
A positive PCR assay on serum or urine is confirmatory for Zika virus infection. Because of complications with serologic testing, samples that are presumptive positive, equivocal, or inconclusive on IgM testing at the WSLH must be forwarded to CDC for confirmation by the plaque reduction neutralization test (PRNT). Turnaround time for PRNT testing at CDC is currently about four weeks.
All requests for Zika virus testing must be approved by a Wisconsin DPH communicable diseases epidemiologist.
Pregnancy & Birth
If a pregnant woman has laboratory evidence of Zika virus infection (regardless of whether she has symptoms), the Bureau of Communicable Diseases Epidemiology Section (CDES) contacts the Bureau of Community Health Promotion (BCHP) and the patient is included in the CDC Zika Pregnancy Registry. The purpose of the registry is to collect enhanced surveillance data about pregnant women and their infants. BCHP staff works with providers to gather and report relevant information to CDC. In addition, BCHP is conducting active surveillance to identify infants with birth defects associated with Zika virus infection, which may result in the identification of additional Zika virus infections and/or cases.