Zika outbreak: A tale of mosquitoes, blood, sex, and vaccines

At this point it’s pretty safe to say that the Zika virus is like Dengue on steroids. Not only has it been linked to birth defects like microcephaly, but there is also the possibility that it may be transmitted through sexual contact – person-to-person, that is, not between a human and a mosquito, just in case you were picturing a Mansquito. Granted, these links are still tenuous at best, but do warrant further research. For example, the World Health Organization has urged for further investigation into the sexual transmission of the Zika virus.

The call comes after the first known case of Zika virus transmission in the United States was reported in Texas on Tuesday (or This Tuesday in Texas, if you’re a wrestling fan). The Dallas County Department of health tweeted that the person was no infected through a mosquito bite and had not traveled to South America, but did have intercourse with someone who had traveled to Venezuela. The Texas Department of State Health Services, on the other hand, was more circumspect, stating that “case details are being evaluated, but the possibility of sexual transmission from an infected person to a non-infected person is likely in this case.”

Referring to the Dallas case, WHO spokesman Gregory Hartl told Reuters that “this is only the second mooted case of sexual transmission.” The first would be that of an American man who returned from Senegal in 2008 and is suspected of having infected his wife. “We certainly understand the concern. This needs to be further investigated to understand the conditions and how often or likely sexual transmission is, and whether or not other body fluids are implicated,” Hartl said. He added that the WHO global response team will discuss the sexual transmission report among other issues at its daily meeting later on Wednesday. “There are many things we don't know about Zika. Lots of surveillance is needed ... We have our team set up and are sure there will be lots of progress quickly.”

On a related subject, the American Red Cross as issued a ‘self-deferral’ notice for people who have visited Mexico, the Caribbean, or Central or South America during the past four weeks to wait at least 28 days before donating  blood, even though “the risk of transmission through blood donation continues to be extremely low in the continental U.S.” Additionally, donors who give blood and later develop symptoms consistent with the Zika virus within 14 days of donating are requested to notify the Red Cross so the product can be quarantined. Red Cross microbiologist Susan Stramer said the sexually-transmitted case on Zika in Texas coincided with, but did not prompt the self-deferral notice.

In the vaccine front, developing one for the Zika virus may be even more difficult than creating one for Ebola, as scientists know even less about the former than the latter. For instance, there are 1,043 mentions of Ebola in the Thomson Reuters Derwent World Patents Index, as opposed to only 30 for Zika. Similarly, there have been 4,000 high-profile academic papers on Ebola since 2001, but only 108 on Zika, according to the Web of Science. “To be useful, a Zika vaccine would need to be effective and safe, but it's difficult to do both. It’s a balancing act.” expert on viruses at Britain's University of Reading Ben Neuman told Reuters. To compound the problem, pregnant women are seldom included in clinical trials. “It raises special safety considerations in vaccine development because you want to make sure any vaccine is safe for both mother and child,” Japan's Takeda Pharmaceutical vaccine head Rajeev Venkayya told Reuters.

And of course there is also the almighty dollar. There isn’t a lot of profit to be made from a vaccine that might be used only in teenage girls from countries and regions where the Aedes aegypti mosquito lives. “It's a public health good initiative, it's not necessarily a commercial initiative,” Berenberg Bank analyst Alistair Campbell said. “Zika is something that has cropped up suddenly and may well dissipate, so there may not be a sustainable annual cohort of patients for vaccination.” Nevertheless, Takeda, Sanofi, GlaxoSmithKline, the Butantan Institute in Brazil, Indian biotechnology company Bharat Biotech, and Pfizer Inc, Johnson and Johnson and Merck, as well as the U.S. National Institutes of Health, and the Public Health Agency of Canada have all started working on a potential vaccine, ranging from feasibility studies to estimating that an experimental vaccine might be able to be used on a limited emergency basis by late 2016, as Canadian researcher Gary Kobinger told Reuters.

Hopefully that will be the case, seeing as how suspected and confirmed cases of newborns with microcephaly associated to Zika in Brazil have increased to 4,074 as of January 30th from 3,718 a week earlier, according to the Brazilian Health Ministry. Eight in every 10 of the birth defect cases are in the impoverished northeast region of Brazil where the virus was first detected in May, and one-third of them are in the state of Pernambuco where doctors first suspected the virus was infecting pregnant women and stunting the brain development of the fetuses. The government of the South American country is currently engaged in an effort to eradicate the Aedes aegypti mosquito. There is cure or specific treatment for the Zika virus other than relieving the symptoms – e.g., acetaminophen or paracetamol to manage fever and pain.

Meanwhile in the United States, health experts fear the mosquito’s habits might render it hard to kill. “We know fogging (outdoor pesticide fog sprayed by truck and airplane) is not effective,” Gonzalo Vazquez-Prokopec of Emory's School of Public Health's Department of Environmental Sciences said. Aedes aegypti is Blade’s nightmare; it feeds on human blood during the day and lives under beds and inside closets – basically our parents all lied to us about there not being anything hiding in those two places. According to Vazquez-Prokopec, controlling the mosquito requires spraying pesticide under beds, on the walls and in closets. White House spokesman Josh “HMS” Earnest said the risk of transmission is now “quite low” but “we want to make sure that we have got a strategy to try to limit the spread of this disease when” temperatures rise. “If it's going to happen, I think it will happen in the warmer months, likely in April and May,” dean of the National School of Tropical Medicine at Baylor College of Medicine in Houston Dr. Peter Hotez said, to drive the point farther home.

Elsewhere, the WHO has said European countries should start preparing to protect their populations against Zika now that summer and spring are drawing near. “Now is the time for countries to prepare themselves to reduce the risk to their populations,” WHO's Europe chief Zsuzsanna Jakab said in a statement. “Every European country in which Aedes mosquitoes are present can be at risk for the spread of Zika virus disease. A number of travelers infected with Zika have entered Europe, but the disease has not been transmitted further, as the mosquito is still inactive. With the onset of spring and summer, the risk that Zika virus will spread increases.” WHO officials have expressed concern that it could also hit Africa and Asia.

Related:  Zika virus + birth defects = international health emergency