Infection
U.S. Scientists Deliberately Infected People With Zika—Here’s Why
Oct
Topline
Researchers in the United States have for the first time deliberately infected people with Zika virus, a breakthrough that could help advance our understanding of the disease and accelerate efforts to develop treatments and vaccines.
Key Facts
Researchers have found a way to safely and effectively infect human volunteers with Zika virus for the first time, according to results presented at the annual meeting of the American Society of Tropical Medicine and Hygiene in Chicago this weekend.
The researchers, led by Johns Hopkins professor Anna Durbin, recruited 28 female volunteers to see whether they could be safely infected with one of two different Zika strains, all of whom agreed to stay in a medical unit until they were no longer contagious and for their own safety.
Of the 20 women deliberately infected with the virus—10 for each strain with the remaining eight receiving an inert placebo—all developed laboratory-confirmed infections but only mild illness.
Such studies, often called challenge studies or controlled human infection models, open the doors for researchers to investigate how the immune system responds when exposed to a particular pathogen and makes it easier to test new vaccines and treatments.
Krishanthi Subramaniam, a research fellow at the U.K.’s University of Liverpool who is part of a team developing a Zika vaccine, told Forbes a human challenge model for Zika would be “extremely valuable” for researchers like herself and could mark a “turning point” for efforts to test new vaccines and treatments.
Subramaniam explained that while there is still ongoing transmission of Zika in Latin America, the overall prevalence is low and researchers struggle to recruit “the robust levels of infected subjects needed” to run rigorous late-stage clinical trials.
Key Background
Scientists have known about Zika since the virus was first discovered in Uganda’s forest of the same name in 1947 but was considered to be an obscure and benign infection. For most people, the mosquito-borne virus triggers no or mild symptoms. That perspective changed in 2015, when Zika exploded across Brazil and through the Americas, where it was linked to a variety of neurological birth defects among children born to parents who had been infected with the virus while pregnant. The outbreak sparked a global health panic and the World Health Organization declared Zika a public health emergency of international concern, the fourth it had made such a designation after the H1N1 swine flu pandemic in 2009, a still ongoing declaration for polio in 2014 and the 2014 Ebola outbreak in West Africa. Zika transmission has been confirmed in 89 countries and territories and there have been at least 200,000 confirmed Zika cases during the outbreak, though health officials warn surveillance is limited for Zika. Cases worldwide have fallen since 2017, which has complicated efforts to research the virus and develop vaccines and treatments. There are no vaccines or treatments available to prevent or tackle Zika infection, which has raised numerous ethical and practical boundaries for efforts to develop human challenge models like Durbin and her team. “It is a very tricky balance because you want to test vaccines and treatments for Zika but you also need to ensure the utmost safety of the participants and the public,” Subramaniam said.
Crucial Quote
“Sadly, we are seven years since the 2016 epidemic and there are still no licensed vaccines for Zika,” Subramaniam told Forbes, noting that there are “several in development” including that being developed by the team at Liverpool. Subramaniam said early stage Phase 1 testing is underway at the Royal Liverpool Hospital, adding that results from tests in mice are “very encouraging.”
Tangent
The kind of mosquitoes that transmit Zika thrive in warm environments and experts warn climate change will help expand the range of areas they can occupy. As well as Zika, these mosquitoes can also carry viruses like dengue, chikungunya and yellow fever, which are major health threats. Parts of the U.S. are already hospitable to these insects and scientists warn these diseases could gain a foothold and establish a permanent presence in many parts of the country. “Viruses transmitted by mosquitoes will be a challenge that we will all have to face,” Subramaniam said, warning that countries that have never before seen Zika transmission could soon do so. “Given the changes associated with global warming, mosquitoes are adapting fast and this ecological plasticity means they are encroaching into new habitats, which means countries not endemic for Zika may start seeing transmission.”
What To Watch For
Durbin said there are plans to test deliberately infecting male volunteers with Zika next. The virus is known to be sexually transmitted and part of the study will be to assess how long Zika can remain infectious in semen, Durbin said.
Further Reading
A Single Mutation Could Make Zika Virus More Infectious And Able To Break Through Immunity, Researchers Warn (Forbes)
Scientists infect volunteers with Zika in hunt for vaccines, treatments (Reuters)
Painful Dengue May ‘Take Off’ In United States—What To Know About The ‘Breakbone Fever’ Virus (Forbes)
