How we are fighting the spread of Zika
On Feb. 1, the World Health Organization declared a Public Health Emergency of International Concern. This was in response to the increase in neurological disorder cases coinciding with the recent outbreak of Zika virus infections. A week later, the Centers for Disease Control and Prevention increased their response efforts to the highest activation level.
This fast-moving disease is one of many viruses transmitted to humans by mosquitoes. According to the American Mosquito Control Association, over one million people worldwide die from a mosquito-borne disease every year.
Therefore, it is no surprise that researchers past and present have been working from every angle to develop a prevention strategy. While some concepts are still being tested, others are being applied to the current Zika virus outbreak.
Originating in the Zika Forest of Uganda in 1947, the Zika virus made its way across the Pacific and is currently active in 29 countries in the Americas, four countries in the Pacific, and one country in Africa.
“The biggest concerns to the medical community are the devastating, unexpected consequences of Zika infection in some unborn babies as well as a serious neurologic condition called Guillain-Barre syndrome, which seems to affect a small proportion of Zika infected people of both sexes and different ages,” said Dr. Claire Panosian, who specializes in infectious diseases at the Ronald Reagan UCLA Medical Center
On the other hand, the majority of people with Zika show no symptoms. According to the CDC, 80 percent of cases are asymptomatic and won’t even be diagnosed. And, while it is not contagious through indirect contact, cases of transmission through blood transfusion and sexual contact have been reported, potentially resulting in a local spread of the disease.
A person is only able to transmit the virus during the viremia phase of the illness, meaning the virus is in their blood. For Zika, this period lasts about three to 12 days after the mosquito bite, regardless of whether they are showing any symptoms. The CDC has recently reported that the virus is present in semen longer than in blood, though the exact amount of time was not specified.
Transmission has also been found to occur from infected, pregnant mothers to their unborn child during pregnancy and, although rare, during the time of birth. These children may be at risk for microcephaly, a condition in which babies are born with abnormally shrunken heads, though this link has not been conclusively proven as of yet.
While there is no specific anti-viral treatment or vaccine, the CDC and WHO have been working to control the Zika outbreak by supporting clinical and mosquito reduction efforts.
“In tropical countries, motivating and empowering people to eliminate mosquito breeding sites around their homes and also protect themselves against mosquito bites is a huge challenge,” said Panosian. “To achieve this goal, there has to be a partnership between the community and the government, as well as greater investment in public health infrastructure.”
On the science front, medical and public health researchers have been pursuing preventative measures for mosquito-borne illnesses in general, such as dengue, malaria, yellow fever and chikungunya. In a collaborative effort, scientists have been working to find answers and solutions to these fast-paced diseases.
“We’re bringing everyone together to gather information,” said Kevin Njabo, Africa Director at the Center for Tropical Research at UCLA. Scientists that specialize in the study of insects and environments, “look at patterns and describe trends and give information to genealogists,” said Njabo.
These genealogists have already begun studies on self-limiting genetic technology, in which the genes of male mosquitoes are altered in a way that results in the death of their offspring. So far, field trials have shown promising results in this method of suppression.
Other work has been done to engineer mosquitoes that are resistant to the parasite that causes malaria. Laboratory testing has shown that the resistant genes are in fact being passed on to the offspring, indicating good potential for future field tests.
Using the findings of microbiologists, who study microorganisms like viruses and bacteria, scientists have investigated the use of a bacteria called Wolbachia, which has shown the ability to inhibit the replication of dengue, chikungunya and malaria parasites. By introducing this bacterium to mosquitoes, they are able to reduce the spread of the virus.
Other researchers have been working to get a step ahead of the mosquitoes. With a doctorate degree in biology, Njabo’s work involves a full analysis of the characteristics of the specific genus of mosquito carrying and transmitting the virus and the environment in which they live.
“We can create an environmental envelope to predict areas with similar traits,” said Njabo. “We then build models that can predict where the virus will move in the U.S., so we can then look into this area and have a plan of action.”
Dr. Panosian agrees that research like Njabo’s is a critical step in controlling the current outbreak. “The focus should rest for now on the mosquito vector,” said Panosian. The Aedes aegypti and Aedes albopictus mosquitoes have been identified as primary vectors, or vehicles for transmission, for the Zika virus. Both of these are already present in over 30 states.
While there is no evidence that mosquitoes in the U.S. are carrying the virus, and no locally transmitted cases have been found as of yet, there has been over 100 travel-associated cases across the country affecting 25 states. These travel related cases occur when a person goes abroad to one of the countries with active transmission and contracts the virus before traveling back to the U.S. In California, six cases have been found over the last three years.
With the newly identified transmission methods, the majority of patients being asymptomatic and the danger to unborn children, finding a solution is not going to be easy.
“It will still take months to years to fully understand the spectrum of disease,” said Panosian. “There are no quick answers to a fast-moving problem like Zika—a virus which is both “benign” and occasionally devastating.”