US scientists infect volunteers with Zika in hunt for vaccines, treatments

In a groundbreaking study, researchers in the United States have demonstrated that they can safely and effectively infect human volunteers with the Zika virus. This is a significant stride towards understanding the disease better and developing potential vaccines and treatments. The study, known as a 'controlled human infection model', has previously been controversial due to the risks it posed to participants and the absence of treatments for Zika. However, US regulators and the World Health Organization have deemed the new model, developed by a team at the Johns Hopkins Bloomberg School of Public Health, as safe and scientifically significant. Zika is a viral infection transmitted by mosquitoes, which is usually mild or asymptomatic. However, a major outbreak in the Americas in 2015 and 2016 revealed its potential dangers to pregnant women and fetuses, causing severe birth defects such as microcephaly, a disorder where a child is born with an abnormally small head and brain. Currently, there are no vaccines or treatments for Zika, and the outbreak in the Americas concluded before new ones could be fully tested. Infections have since decreased worldwide, with about 40,000 reported last year from that region. However, the WHO has cautioned that surveillance can be inconsistent, and transmission patterns for Zika are not well understood. Climate change is also likely to exacerbate the spread, which is already prevalent in 91 countries. Anna Durbin, the Johns Hopkins professor who led the study, emphasized the importance of developing countermeasures as infections could resurge. She also highlighted the mental health burden on pregnant women in endemic regions, who worry about the virus and their babies but have limited protection options. Durbin and her colleagues used two strains of Zika to infect 20 female volunteers who were not pregnant or lactating. All developed laboratory confirmed infections, with mild illness. Eight others received a placebo. To minimize the risks, the patients were admitted to an inpatient unit and monitored until they were free of the virus. They agreed to use birth control methods for two months. The next step is evaluating the strains in male volunteers, in part to assess how long the virus, which can be sexually transmitted, remains infectious in semen. Durbin mentioned that several vaccine manufacturers have already requested to use the strains to test experimental products. The data was presented at the annual meeting of the American Society of Tropical Medicine and Hygiene in Chicago.