The Zika virus stands to cost the United States billions of dollars, even if few people are infected.
Researchers from several American institutions have calculated that the "virus from Hell" could result in total costs ranging from $183 million to over $1.2 billion, depending on infection rates in several at-risk states in the South.
The researchers warn that infection rates could engender costs that exceed the amounts of money the U.S. government may give for prevention and treatment, if the recent debates over funding are any indication.
"We had the sense that Congress was really not aware of the depth and breath of the vulnerability of the Gulf Coast regions," study co-author Dr. Peter Hotez said in an interview with CNBC.
"One of the problems is we do not do active surveillance for Zika along the Gulf Coast," said Hotez, dean for the National School of Tropical Medicine at Baylor College of Medicine . "So we still do not know the true number of cases that happened last year. And we are not going to know that until we see the number of babies born with birth defects due to Zika going into the summer months. So we are not out of the woods yet, with respect to last year's epidemic."
And periods of warm weather over the last several months have coincided with higher numbers of Aedes aegypti mosquitoes, which carry the virus, leaving scientists wondering where Zika could spread next.
The team published its results Thursday in the journal PLOS Neglected Tropical Diseases.
The researchers focused on various levels of infection across Alabama, Florida, Georgia, Louisiana, Mississippi and Texas — states with climates well suited to the mosquitoes that carry the disease. In addition, poverty in the region contributes, through factors like poor housing and environmental degradation that can boost to mosquito numbers and infection rates. And then there is all the travel passing through major gateways in the region.
A Zika attack rate of 0.01 percent across this region would cost society $183.4 million, including both direct medical costs and productivity losses, resulting from the burden of the disease.
Raising that by one order of magnitude, to 0.1 percent, would cost $274.6 million. A 1 percent infection rate would cost $1.2 billion, and 2 percent would exceed $2 billion.
These estimates are not unimaginable or even especially pessimistic. In fact, the team aimed to be a bit conservative.
Consider that Zika's infection rate in French Polynesia has exceeded 10 percent — five times the worst-case scenario the researchers outline here. Infection rates in Puerto Rico for the similar chikungunya virus also exceed 10 percent.
This conservatism was influenced in part by the fact that Zika has not quite hit Haiti as hard as expected. The region has a similar climate to other areas affected, and has even higher levels of poverty than Puerto Rico.
This surprised many researchers, Hotez said. Data like these, along with many of the remaining questions about Zika's health effects, reinforce the notion that "we don't know more than we do know," Hotez said.
In addition, the team is not factoring in effects that could ripple beyond these six states. They also do not include any the potential effects on tourism or travel in these states, and they are not considering further medical costs and lost productivity and medical costs that may result from fears of infection, or from infections that strike visiting family and friends coming from elsewhere in the country.
"As we aimed to be conservative in our estimations, our model in many ways may underestimate the economic burden of Zika," the team said. "Our analyses indicate that the health and economic burden of even low attack rates of Zika in the Continental US would be both substantial and enduring."
A strain of the Zika virus first confirmed in Brazil in 2015 has now spread to more than 40 countries, and many researchers believe the disease is already present in the United States. Its symptoms can at first resemble those of far less dangerous diseases, such as the flu, but its effects can severely impair people for life.
It has been linked to microcephaly in babies born to infected women. In these cases, the brain of unborn or infant children fail to develop, leading to lifelong mental impairment and abnormally small skulls.
Zika has also been linked to Guillain-Barre syndrome, a disease where the immune system attacks the nervous system.
The researchers say their study is an attempt to better inform the debate over how much money the U.S. government should devote to Zika prevention and treatment.
For example, the Obama administration had requested $1.8 billion from Congress for prevention, which some had criticized for being excessive. While Congress has since authorized $1.1 billion in funding, the researchers say both sides of the continuing debate over funding levels have limited data on which to base their arguments, without an analysis of the full economic impact of the disease.
"I think it is a wake-up call, not only with regard to the health impact but also the economic impact, and I think the stakes are high," Hotez said.