Health officials reported Monday the first case of Zika virus in the state of Texas that was acquired from a local mosquito rather than from travel outside the state. With this announcement, Texas joined Florida as the only states in the U.S. to report locally acquired Zika virus infections. The Zika virus has entered the national stage only recently, as an outbreak that began in Brazil in May 2015 has gradually spread northward, reaching Florida in July of this year.
Zika virus is transmitted between humans by Aedes mosquitoes, primarily Aedes aegypti, and by unprotected sexual contact. Zika infection in pregnant women has been linked to miscarriage and severe neurological defects in surviving infants. With no vaccine currently available, the focus of Zika virus control has been containment through detection of infection in both humans and mosquitoes and through mosquito population control. The latter is an effort in which all must participate, both as individuals and as communities, to prevent Zika and other mosquito-borne illnesses in our area.
Currently, the only way to prevent Zika infection is to avoid mosquito bites. Although levels of fear have reached frenzied levels over the past year, here in Ohio we don’t need to worry about Zika virus. However, it is still essential that we devote both public resources and private attention to mosquito control efforts. We may not get Zika virus, but many other infections are transmitted by mosquitoes. Ohio has endemic, or constant low-level, transmission of West Nile virus, and to a lesser extent the La Crosse encephalitis and St. Louis encephalitis viruses. These three viruses are all transmitted by different species of mosquitoes that occur commonly in Ohio.
The Centers for Disease Control and Prevention reports that at least 65 people have died in Ohio from West Nile infection since the virus arrived in the state in 2002, more than four times as many deaths as have been reported from Zika infection in the Americas, according to the Pan-American Health Association. Like Zika, infection with these three viruses is usually asymptomatic, meaning that it can be difficult to know if there is active virus transmission in the area without blood testing. Children and the elderly are most at risk for severe or life-threatening effects. Zika almost exclusively causes death or severe impairment in fetuses rather than infected adults, while infection with West Nile, La Crosse or St. Louis encephalitis virus is more likely be fatal to the person infected. All three can invade the central nervous system and cause encephalomyelitis, an inflammation of the brain and spinal cord, and 7 percent of the reported cases of West Nile in Ohio between 2002 and 2015 proved fatal.
Unlike Zika virus, these viruses also live in birds and other animals in Ohio, which means we can never eradicate them. Malaria is a disease that, like Zika, is only transmitted between humans and mosquitoes, and it was eliminated from Ohio when changes including the draining of wetlands and the use of screened windows drastically reduced mosquito bites. Eventually, infected mosquitoes died off and recovered human patients were no longer able to reinfect the mosquito population. Zika can similarly be eliminated in places like the U.S. where we can avoid mosquito bites through simple steps like keeping unscreened windows and doors closed and staying inside at dusk. In contrast, elimination of West Nile and similar viruses would require destruction of an ecosystem, a feat which is both virtually impossible and highly undesirable.
We must always continue to monitor and control local mosquito populations to prevent human infections. Both the people and the government have a responsibility to focus our energy and resources on mosquito control in Ohio, with an eye to protecting ourselves and our children against dangerous endemic infectious diseases rather than against exotic diseases farther south. Female mosquitoes lay their eggs in standing water, so we can do our part by reducing the availability of places for them to do so. Rain barrels, planters, buckets and used tires are all common places for mosquitoes to lay their eggs. Covering rain barrels, storing buckets empty or upside down and preventing water from building up in tires and planters are all easy ways to help reduce mosquito populations in your area.
Towns and cities can help do their part to reduce standing water by redesigning wastewater management systems, since sewer systems are common egg-laying sites and can even sustain adult mosquitoes through the winter. A recent project conducted by myself and other students in Professor Mary Garvin’s disease ecology class found mosquitoes emerging from multiple storm drains on Oberlin’s campus, confirming that the Oberlin wastewater management system can breed mosquitoes. Local administrations can also coordinate with state public health officials to put natural larvicides in breeding habitats.
Although the substantial news time that has been devoted to Zika infections has made the risk seem high and the threat immediate, our efforts are best focused on the less-discussed diseases that are already present here in Ohio to help protect ourselves and our families.