By Robert M. Califf, M.D., and Luciana Borio, M.D.
Zika virus was first identified in 1947 in Uganda and for decades only sporadic cases and a few outbreaks were recognized in a number of locations, including parts of Africa, Asia, and the Pacific. Since 2015, the situation has changed dramatically, with 48 countries and territories reporting a first outbreak of Zika virus as of July 2016.
In the United States, cases of Zika virus disease acquired by the bite of an infected mosquito have only been reported in U.S. territories; to date, cases of Zika virus infection reported in the continental United States have involved travelers and in some instances their sexual contacts. However, given the number of Zika cases among travelers visiting or returning to the United States and the increased mosquito activity in the summer months, we expect that imported cases could result in local spread of the virus in some areas of the United States.
The FDA is taking important steps to rapidly respond to the Zika virus outbreak. We are engaged with our partners across the U.S. Government, the private sector, and the international community—including the World Health Organization and ANVISA (the Brazilian Health Regulatory Agency)—to help minimize the impact of this outbreak.
Protecting Tissues and the Blood Supply
One of the FDA’s first actions was to take important steps to help protect the safety of the blood supply. The FDA issued guidance in February 2016 recommending the deferral of individuals from donating blood if they have been to areas with active Zika virus transmission, were potentially exposed to the virus, or have had a confirmed infection.
The guidance also recommends that areas with active Zika virus transmission, like Puerto Rico, obtain whole blood and blood components from areas of the United States without active virus transmission unless a blood donor screening test for Zika virus is used.
Because there were no blood donor screening tests available for Zika virus at the time, HHS arranged for and funded shipments of blood products from the continental U.S. to Puerto Rico to ensure an adequate supply of safe blood for residents until a blood donor screening test became available.
The FDA worked closely with developers in a highly accelerated time frame to make available an investigational test for blood screening in March 2016. The availability of this investigational test, which has been in use in Puerto Rico since early April, has allowed blood establishments to safely collect blood in areas with active Zika virus transmission. A second investigational blood screening test was made available in June 2016. Together, these tests have also enabled blood donor screening to be put in place in areas of the United States where local virus transmission is anticipated, but not yet detected, helping to maintain the safety of the blood supply.
Zika virus also poses a risk for transmission by human cells, tissues, and cellular and tissue-based products (HCT/Ps) such as corneas, bone, skin, heart valves, and semen used for medical, surgical, or reproductive procedures. Because of this risk, the FDA issued guidance recommending that donors of HCT/Ps be considered ineligible if they were diagnosed with Zika virus infection, were in an area with active Zika virus transmission, or had sex with a male with either of those risk factors, within the past six months.
Supporting Diagnostic Development
The ability to accurately detect and diagnose Zika virus infection is critical for a robust response to this public health threat. The FDA is actively working with manufacturers to support their diagnostic development programs, helping to ensure that their tests are properly validated before they are used to inform patient care.
This collaboration has been very successful, and since the beginning of the year, we have authorized the use of five diagnostic tests for Zika virus under FDA’s Emergency Use Authorization authority—four tests to diagnose active infection and one test to assess whether individuals who may have recently been exposed to Zika were actually infected. This test is especially important for women given the link between Zika virus infection and microcephaly and other poor pregnancy outcomes in babies of mothers who were infected with Zika virus during their pregnancy.
Strategies to Suppress Mosquito Population
FDA—as well as our colleagues at EPA— are reviewing the use of innovative strategies to help suppress the population of virus-carrying mosquitoes to help mitigate the threat of vector-borne epidemics, such as Zika virus, which is thought to spread to people primarily through the bite of an infected Aedes aegypti mosquito.
Recently, the FDA released for public comment a draft environmental assessment (EA) submitted by Oxitec, Ltd. (Oxitec). The EA assesses the potential environmental impacts of a proposed field trial of the company’s genetically engineered (GE) Ae. aegypti mosquitoes. The FDA also released for public comment a preliminary Finding of No Significant Impact (FONSI) agreeing with the conclusion in Oxitec’s draft EA that the proposed field trial of the company’s GE mosquitoes would not result in significant impacts on the environment.
The goal of the proposed field trial is to determine whether released Oxitec GE mosquitoes will mate with local wild-type Ae. aegypti and suppress their population at the release site. The FDA is reviewing the thousands of comments received during the public comment period before determining whether to finalize the EA and FONSI or prepare an environmental impact statement (EIS).
Oxitec will not proceed with the field trial of the GE mosquitoes until FDA issues its final EA and FONSI or EIS. Oxitec’s GE mosquitoes are one possible approach that could be incorporated into an integrated vector control program to help mitigate the threat of vector-borne epidemics; however, it is too early to say with any certainty whether such an approach would be successful.
Facilitating Medical Product Development
There are currently no vaccines or treatments for Zika virus that have been shown to be safe and effective. Facilitating the development and availability of vaccines is one of the highest priorities for the FDA and the international community. The FDA continues to actively engage with commercial and government developers, including the NIAID and BARDA, to advance the development of investigational vaccines for Zika virus as soon as possible.
We are also working with ANVISA to assist in their efforts to expedite the development of vaccines for Zika virus. As was recently reported, a commercial company announced plans to begin evaluating the first investigational Zika virus vaccine in a Phase I clinical study.
Unfortunately, during outbreak situations, fraudulent products claiming to prevent, treat or cure a disease almost always appear. FDA is monitoring for fraudulent products and false product claims related to Zika virus and will take appropriate action to protect consumers when necessary.
More than 120 FDA staff from across the Agency are responding to the Zika virus outbreak, working together to address the complex range of issues that this evolving epidemic continues to present in order to protect and promote the public health, both domestically and abroad.
This type of teamwork exemplifies the capacity of people at FDA to rally together to solve problems, often with little explicit credit other than the satisfaction of meeting the mission of promoting and protecting the public health. There are many fundamental scientific questions that need to be addressed with respect to Zika virus, and our scientists are working to help answer some of these questions in our own laboratories. We stand ready to use our expertise and authorities to the fullest extent to help facilitate the development and availability of products that may help mitigate the Zika virus outbreak.
Visit our Zika response web page for more information, including the latest Zika virus response updates from FDA.
Robert Califf, M.D., is Commissioner of the U.S. Food and Drug Administration
Luciana Borio, M.D., is FDA’s Acting Chief Scientist