‘Limited outbreaks’ of Zika virus foreseen in US

Officials from the CDC reiterated their optimism that the risk for a widespread outbreak of Zika virus remains minimal in the United States during a news conference today, while WHO officials meeting in Geneva were not nearly as confident about the impact the virus is having in other parts of the world.

According to Anne Schuchat, MD, principal deputy director of the CDC, there have been 31 cases of travel-related Zika virus cases in 11 states and Washington, D.C., since 2015. While officials did not immediately make state-by-state figures available, known cases recently have been reported in Texas, Illinois, Florida, Hawaii, Virginia, New Jersey and New York. Schuchat said that an additional 20 laboratory-confirmed cases have been reported in Puerto Rico and the U.S. Virgin Islands. Officials emphasized that there is currently no local transmission of Zika virus in the U.S., however, this scenario is likely, due to the commonality of the Aedes aegypti mosquito vector in the southern U.S.

Anne Schuchat

“The virus is spreading throughout the Americas, and we expect more countries to be affected,” Schuchat said at the news conference. “It is possible, even likely, that we will see limited Zika outbreaks in the U.S.”

She said the potential for a widespread outbreak is significantly reduced because U.S. urban areas are not as densely populated as South and Central American cities. Other beneficial characteristics of U.S. cities noted by officials included common use of air conditioning and better mosquito control measures. Due to the lack of effective communitywide mosquito control options, however, individual deterrents must be relied on to reduce the risk for Zika infection.

“Community mosquito control may be difficult because the current methods have some shortcomings,” Schuchat said.

According to Anthony S. Fauci, MD, director of the National Institute of Allergy and Infectious Diseases, due to the relative newness of Zika virus, there currently is little research available. As a result, the NIH intends to immediately fill this deficit by funding and accelerating studies on the history of the disease, pathogenesis, diagnostics, vaccines and therapeutics.

Fauci said NIAID is currently working on vaccine candidates to prevent Zika virus infection.

Anthony S. Fauci

“We already have existing vaccine platforms to use as a sort of jumping off point,” he said “First, a DNA-based vaccine using a strategy very similar to what we employed for ... the West Nile virus. This vaccine was found in a phase 1 trial to be both safe and immunogenic. Second, a live-attenuated vaccine building on similar and highly immunogenic approaches used for the closely related dengue virus.”

Officials confirmed that factors related to climate change and El Nino could make transmission of the virus more widespread; however, Fauci said climate change also could reduce the mosquito population, thereby reducing the threat for Zika outbreaks. Schuchat also stated that the reported presence of Zika pathogens found in semen and a recent reported case of Zika infection via sexual contact suggest that sexual transmission of Zika virus is “biologically plausible.”

Fauci also emphasized that because there is no local transmission within the U.S., the risk for Zika virus is very low, adding, “There is essentially no risk at all.”

“For the average American, who is not traveling, this is not something they should worry about.” Schuchat said.

WHO: Zika ‘spreading explosively’

Meanwhile, WHO officials, gathered at an executive board meeting today, were not as optimistic about Zika virus outside of the U.S.

“The situation today is dramatically different,” WHO Director-General Margaret Chan, MD, said during the briefing. “Last year, the virus was detected in the Americas, where it is now spreading explosively. As of today, cases have been reported in 23 countries and territories in the region. The level of alarm is extremely high.”

Margaret Chan

During the briefing, WHO officials said their concerns on the global threat of Zika virus center on four factors. These included the association of Zika virus with microcephaly and Guillain-Barré syndrome, the threat of international spread due to the commonality of the A. aegypti mosquito vector, the lack of immunity in newly affected areas, and the lack of vaccines, effective treatments and practical diagnostic tests.

WHO officials also cited concern over this year’s El Nino weather pattern, which could increase the global mosquito population. – by David Costill