West Nile, Chikungunya, Zika – exotic names that have become all too familiar in the United States over the last couple of decades.
State Epidemiologist Timothy F. Jones, MD, noted, “We are certainly seeing an uptick in the number of mosquito-borne diseases.” While not prepared to call these vector-borne illnesses an emerging pattern, Jones said they are starting to come to North America ‘fast and furious.’
Jones, who serves as director of the Tennessee Department of Health Communicable and Environmental Diseases and Emergency Preparedness, said “Zika virus is one that before 2007, we’d only had 14 cases in the world that we knew about in Africa and Asia.” Since then, he continued, there have been a couple of big outbreaks in the Pacific Islands … and then came Brazil.
“In late 2015, a significant increase in the number of infants born with microcephaly was detected in Brazil,” Jones said. “At the same time, they noticed an outbreak of the Zika virus. The assumption is they are connected, but there is still a lot of work to be done to prove the link.”
Data published in Morbidity and Mortality Weekly Report (MMWR) at the end of January, noted a Zika virus outbreak was reported in northern Brazil in early 2015. By September, health authorities began receiving reports from physicians in the region of an increase in the number of infants born with microcephaly.
In a cohort of 35 infants with microcephaly born August-October 2015, all 35 had mothers who had lived in or traveled to Zika virus-affected areas of the country. Testing for other congenital infections in these infants came back negative. Cerebrospinal fluid samples from the 35 infants have been sent to a reference laboratory in Brazil for Zika virus testing, however results of the testing were not available at press time.
Other Brazilian researchers have found increased microcephaly in the region predating the Zika virus outbreak, which could point to other factors in the area causing or contributing to the congenital defect. However, the most severe cases were clearly on the rise in late 2015, and it’s also possible the Zika virus has been present in the northern region of Brazil for longer than health officials initially thought.
In addition to concerns for pregnant women, an uptick in Guillian-Barré syndrome has coincided with Zika outbreaks in Brazil. After convening a task force of experts, the World Health Organization designated the Zika virus a global public health emergency last month.
Jones, who is the past president of the Council of State & Territorial Epidemiologists and previously worked with the Centers for Disease Control and Prevention, said that the Zika virus has now spread to at least 25 countries, including the United States, and the number of impacted nations continues to rise.
At press time, he pointed out, “We still haven’t had any cases in the United States that haven’t been transmitted here, but we have had cases imported.” In Tennessee, the first confirmed case of the Zika virus was reported on Feb. 9 in a person who had recently traveled to South America. However, Jones doesn’t believe that will be the last case reported here.
“Across Tennessee, thousands of college students, members of faith organizations, healthcare professionals and others are now planning spring trips to warmer locations for either fun or mission work,” he said. “The Tennessee Department of Health cautions travelers headed soon to warmer climates to have an increased awareness about diseases spread by mosquitoes and to make mosquito bite prevention an essential part of their trip planning.”
Similar to chikungunya, he doesn’t believe the Zika virus will blow up into an outbreak that keeps regenerating in the United States like West Nile. “West Nile also infects birds and animals so once it gets into the animal population, it will be there forever,” Jones explained.
With Zika, he continued, “We think the virus probably jumped from monkeys into the human population years and years ago on another continent, but it isn’t a virus that’s going to get into the natural reservoir.”
While it’s possible for a mosquito to bite an infected person who has imported the disease and then spread it to another individual in the community, Jones said it is unlikely widespread outbreaks would occur. “Viruses tend to have very specific hosts they like to live in … and in fact, it’s not just mosquitoes, but very specific types of mosquitoes, that can transmit Zika,” he said of the illness that is primarily transmitted by Aedes aegypti mosquitoes.
So far, three cases of suspected sexual transmission have been reported, which Jones said is very unusual for mosquito-borne diseases and is being vigorously investigated. The CDC said the Zika virus seems to be present in semen longer than blood. However, officials with the CDC stressed there are many unknowns, including how long the virus actually is present in semen, whether it is transmittable by men who never develop symptoms and whether or not women can transmit the virus to sexual partners.
In light of concerns about the Zika virus and pregnancy, interim guidelines were published Feb. 12 in MMWR that recommend men who live in or have traveled to areas of active Zika virus transmission should abstain from sexual activity with their pregnant partner or consistently and correctly use condoms for the duration of the pregnancy.
“There’s no vaccine, and there won’t be for awhile,” said Jones. He added that with the exception of pregnant women, for whom Zika could be very serious, the virus poses no major threat for most people. Jones noted 80 percent of people who contract the Zika virus don’t even know they have it, and the other 20 percent have mild symptoms that last about a week and could include rash, fever, conjunctivitis and joint aches.
“There’s no treatment for it so really all you can do is prevention … and that means prevention of mosquito bites,” Jones continued. Getting rid of standing water, wearing long sleeves, sleeping under mosquito nets in areas where there is active Zika outbreak, and using mosquito repellants are important deterrents not only for the Zika virus but for other mosquito-borne diseases, as well. In addition to DEET repellant that is sprayed on the skin, Jones said there is also Permethrin, which is a chemical repellant meant for use on clothing.
After more than 2,800 cases of chikungunya being reported in 2014 in the United States, provisional 2015 data showed only 679 reported cases in 2015 with all of those occurring in travelers returning from affected areas. Jones suspects the Zika virus might follow a similar pattern.
RELATED LINKS:
AMA Zika Virus Resource Center
Tennessee Department of Health
CDC Division of Vector-Borne Diseases
