The global effort to halt the spread of the Zika virus is intensifying as more than 1 million people in Brazil alone have become infected. The arrival of Zika caused Florida to declare a state of emergency in four counties Wednesday, a day after Texas logged the first case of the virus transmitted in the U.S.
Infectious disease experts generally applaud the World Health Organization for its response so far. This week the U.N. agency declared a global public health emergency in light of the rapid spread of the disease throughout Latin America and the Caribbean, where as many as 30 countries as of Wednesday were listed as destinations where travelers were at risk of contracting the virus.
The response suggests the global health community has learned from the Ebola outbreak in West Africa, the last health crisis that compelled the WHO to declare a public health emergency. Public health experts see the Zika virus as an opportunity to draw attention and resources to other mosquito-borne infections. But they're also concerned the intense public scrutiny could actually divert resources from work with broader impact in the fight against the spread of infectious diseases.
“The thing that we need to do now is invest much more heavily in understanding the kinds of viruses like this so that we can shorten the time period between the next outbreak and our ability to put together a comprehensive response,” said Dr. Ashish Jha, professor of health policy at the Harvard T.H. Chan School of Public Health. “I think right now we're at a point where the science is such that we're just not there, the science takes too long.”
The WHO came under considerable criticism for its handling of the Ebola crisis. Many believe its slow response in the early months of the epidemic allowed the virus to take hold and spread, ultimately infecting 20,000 people and killing 11,000.
“We do live in a post-Ebola world and there were delays in recognizing the severity of the Ebola outbreak and understanding what its trajectory was going to be,” said Dr. Amesh Adalja, senior associate at the UPMC Center for Health Security. “I think based on that, you're seeing a much more proactive, earlier response to Zika from the WHO than we did during Ebola.”
One lasting lesson from the Ebola outbreak is that grave threats lurk in diseases generally thought to afflict people living in remote parts of the world.
“I think Ebola was the beginning of what is probably going to be a whole series of things like this,” Jha said. “Increasingly we are going to see new viruses that we haven't necessarily been aware of spreading much more quickly.”
The sustained scrutiny of how public officials react to highly publicized threats, however, could lead them to overreact, diverting limited resources from combating more dangerous diseases.
“The decision one makes is not free of value judgments,” said Dr. Lee Norman, chief medical officer at the University of Kansas Hospital, Kansas City. “The dollars and people devoted to preventions and cures are not infinite, so therefore it's a matter of robbing Peter to pay Paul.”
But experts are unnerved by the speed with which Zika has spread over the last few months and its potential link to microcephaly, a serious birth defect in which an infant is born with a head significantly smaller than normal. In Brazil the virus is believed to be responsible for as many as 4,000 cases of microcephaly, but so far there have been no proof to show causal effect.
Zika is only the latest vector-borne disease to ascend in recent years. Dengue fever and chikungunya arguably pose more serious public health threats because of the severity of the symptoms and the size of the populations vulnerable to becoming infected.
“New pathogens always attract attention and make headlines,” said Frank Smith, director of No More Epidemics, a five-year global campaign to work with governments toward improving protection against epidemics. “If we look at it in terms of impact on population, we may find after a few years that the threat is really low and there are mitigation measures that we can take—what we're dealing with are very human responses and very emotional responses.”
About 80% of the people infected with Zika never develop symptoms, according to the Centers for Disease Control and Prevention.
Symptoms include fever, rash, joint pain and headache and can last up to a week. Death from Zika is rare, unlike dengue, which kills about 2.5% of the 500,000 people who develop severe illness from the disease each year.
While the first case of Zika to be transmitted in the U.S. was reported this week, dengue outbreaks have occurred in the U.S. for more than a decade.
“Dengue is without question the more lethal,” Norman said. “I think what captures people's emotions is the terror that an unborn baby or a newborn will be badly affected—it almost seems like it is something that is almost lurking.”
Fortunately, the fact that both dengue and chikungunya cases have been reported in the U.S. provides investigators with indicators as to where the next cases of Zika are most likely to show up.
All three viruses are carried by the Aedes aegypti mosquito, which is commonly found in Southern states. Mosquito control is the recommended means of slowing Zika's spread, but experts believe it will spread further in the U.S. as temperatures rise.
“If you're going to start looking for localized outbreaks of Zika in the United States the places to look are where dengue has been,” Adalja said.