How long the Zika epidemic will last appears to be as big a mystery as the contagious virus itself.
A London-based report published last week predicted the current Zika outbreak would dissipate within three years.
The report’s authors based much of their estimate on the supposition that people can’t contract the virus more than once.
One expert interviewed by Healthline agreed with the conclusions. Another wasn’t so sure.
Since the report came out, the Zika virus has cropped up in unusual ways in Utah and Florida.
In addition, the first female-to-male transmission of the disease in the United States was reported.
The researchers’ conclusions
The researchers at Imperial College London said the Zika epidemic is “not containable,” but they expect the outbreak to “burn itself out” in two to three years.
The reasoning is simple.
The researchers believe it is unlikely people will be infected with Zika more than once. Combined with herd immunity, that will leave the virus with an insufficient number of people to infect to sustain the outbreak.
They do predict another Zika epidemic could emerge in 10 years when a new generation of previously unexposed people emerges.
“This mirrors other epidemics, such as Chikungunya — a virus similar to Zika — where we have seen explosive epidemics followed by long periods with few new cases,” said Imperial College Professor Neil Ferguson, a lead author of the research, in a statement.
The Zika virus is transmitted primarily through the bite of an infected Aedes species mosquito.
It causes only a mild illness in most people who contract the disease. However, it can develop into microcephaly and cause serious brain damage in the fetuses of pregnant women who contract Zika.
Nonetheless, the report authors recommend against large-scale efforts to slow the spread of the virus, including eradication of mosquitos.
They said these efforts could simply prolong the outbreak.
"Slowing transmission between people means the population will take longer to reach the level of herd immunity needed for transmission to stop,” said Ferguson.
What the experts think
Dr. Antonio Crespo, an infectious disease specialist at Orlando Health in Orlando, Florida, said he concurs with the researchers’ prediction of a quick flameout on Zika.
He also agrees with the researchers’ contention that people will not contract the virus more than once. He says once a person’s immune system has been exposed to Zika, it should be able to fight it off if it returns.
“It’s like getting a vaccine,” Crespo told Healthline.
He also agrees with the report’s conclusion that Zika will likely return in about 10 years, although Crespo said he doesn’t think the next outbreak will be as widespread.
However, Dr. Lee Norman, the chief medical officer at the University of Kansas Hospital, said the report’s conclusions might be a bit rosy.
“It’s an optimistic view of what could happen,” Norman told Healthline.
Norman noted the conclusions are based largely on the expectation that people will only get Zika once. He said that is not a certainty.
“It’s not a minor ‘what if’ supposition,” he remarked.
Norman pointed out that the dengue virus has four subtypes, so people can contract the disease more than once.
It’s still unknown if Zika has more than one subtype, he said.
Norman did agree with the prediction that the virus could return in 10 years if indeed it petered out in the next three years.
Both Norman and Crespo, however, disagreed with the report’s notion to minimize efforts to control the spread of Zika.
“I would say don’t do anything to slow down the curative methods of the epidemic,” said Norman. “It’s absurd to back off in any manner.”
“I still believe controlling the mosquito population can help decrease the spread of the disease,” added Crespo. “There is value in doing that.”
Both also agreed that the search for a vaccine should continue.
Questions in Utah, Florida
Some Zika cases in Utah and Florida this past week have raised new questions about how easily Zika can spread.
In Utah, the caregiver for a man who died after contracting Zika became infected with the virus himself.
The caregiver has recovered, but authorities still aren’t certain how he came down with the illness.
They say a mosquito bite or sexual contact doesn’t seem to be the cause.
Officials with the Centers for Disease Control and Prevention (CDC) are investigating the case as well as testing other people who came in contact with the infected man.
In Florida, health officials are investigating a “non-travel” Zika case in Miami-Dade County.
Officials said the person who contracted the disease had not traveled to any country where Zika is prevalent.
Florida, Texas, and other parts of the Gulf Coast are considered at high risk for Zika because the mosquito that carries the virus lives in that region.
The cases were revealed amid reports of the first female-to-male transmission of the disease.
CDC officials said it happened in New York City, and is the first known case of a woman transmitting the disease to a sexual partner.
All previously reported cases of sexually transmitted Zika have been from men to their sexual partners.
The new cases came as the U.S. Senate failed to approve a bill that would have provided $1 billion to fight the spread of the Zika virus during the summer months.
As of midweek, the CDC reported 1,306 cases of Zika in the United States. There have been another 2,916 Zika cases in U.S. territories.