Health officials aiming to prevent Zika’s spread
Dozens of cases found in state, but so far none transmitted by mosquitoes
Dozens of Marylanders have been found to carry the Zika virus, but none of those infections have been transmitted by mosquitoes in the state, according to health officials.
Those officials would not say this week whether or not any Southern Maryland residents are among those reported to be infected, citing patient privacy.
All 54 of the infections reported as of Aug. 3 by the Maryland Department of Health and Mental Hygiene are associated with travel to regions reporting Zika outbreaks carried by mosquitoes, according to the agency. That includes most nations in Central and South America and the Caribbean.
However that range of mosquito-borne infections now includes a neighborhood in Miami, and the Centers for Disease Control and Prevention have issued a Zika-related travel advisory for that area, the first in the continental United States.
Maryland’s Zika cases have been scattered all over the state, Dr. Howard Haft, deputy director of public health services for the state, said late Wednesday afternoon. He and others emphasized that all the infections found so far have been in people who traveled to areas where there have been mosquito-borne outbreaks, or who have had sexual relations with someone who did.
Because there are rela- tively few cases in Maryland, it might be too easy to guess a person’s identity based on travel history, St. Mary’s County health officials said, so information about where they were discovered is not being released by the state in order to protect confidentiality.
However, “that policy would change,” Haft said, if mosquito-borne cases surface in Maryland, as they have in Miami.
Heading off that possibility is the current focus of the state’s public health officials, and of the Maryland Department of Agriculture’s Mosquito Control Administration. “We’re working hard to make sure that never happens,” Brian Prendergast, that agency’s program manager said this week.
But those efforts, which focus on preventing the spread of the species of the mosquitoes that can carry the virus, face challenges.
Pregnant women are at greatest risk from Zika, which has been linked to women giving birth to babies with a condition called microcephaly, a birth defect where a baby’s head is smaller than expected. St. Mary’s health officials declined to say if any pregnant women in Maryland have been found to be infected with the virus, but are “strongly advising women who are pregnant or women trying to become pregnant not to travel to these areas [where mosquito-borne infections have been found] or have unprotected sexual intercourse with a person who has recently traveled to these areas.”
Symptoms of the virus can include fever, joint pain, skin rash and conjunctivitis (red eyes), the St. Mary’s County Health Department said. The illness is usually mild with symptoms lasting from several days to a week.
However those symptoms only occur in about 20 percent of people who have the virus. Since the other 80 percent of those infected with Zika show no symptoms, there are almost certainly people in Maryland carrying the virus who have not been diagnosed.
Someone who doesn’t know they have been infected could be bitten by a mosquito, which could bite someone a week later and transmit the virus to them, Haft acknowledged.
In the Zika cases that have been identified, he said, health officials go door to door and tell anyone within a 150-yard radius of that person’s home that they can, if they’d like, be tested for the virus. In those areas they and mosquito control workers also help residents identify places near their homes where the mosquitoes can breed.
There are between 60 to 65 species of mosquitoes in Maryland, Prendergast said, but it’s the Asian tiger mosquito that can transmit Zika from one person to another, and that species is “incredibly common” in Maryland and lives in close association with people. It also bites people at times when other mosquitoes generally don’t. “This is the most aggressive daytime mosquito,” he said.
“These are not swamp mosquitoes; they are container mosquitoes,” Haft said.
That means they can lay eggs anywhere there is as little as half an inch of standing water — puddles, unused toys, old tires, even bottle caps or in the folds of a discarded piece of plastic wrap.
These breeding habits make prevention efforts difficult, but it can also make them effective.
An Asian tiger mosquito does not fly very far from where it is hatched, Prendergast said, “so Mother Nature is doing us a favor in that regard.” If people can be sure that there are none of these mosquitoes in their yard or the neighbor’s yard, the chance of becoming infected with Zika is low, he said.
That’s why state health officials zero in on the areas near people who have been found to have the virus, and it’s why St. Mary’s health officials and the local mosquito control office is looking to stop Asian tiger mosquitoes from hatching in other areas as well.
“The key really is prevention, having people look at their own yards,” Terry Prochnow, the local agency’s division director of public health preparedness and response, said Wednesday.
So the St. Mary’s health department has been reaching out to neighborhood homeowners associations to spread the word, she said. And about once a week, staffers from the health department, along with the Maryland Department of Agriculture, have been going door to door in a St. Mary’s neighborhood to pass out litera- ture, talk about prevention of mosquito breeding and even help residents check their property for standing water. Once a week, empty, scrub, cover or throw out items that hold water, they advise.
“We work with the health department to inform people what to look for in their neighborhood,” Ralph Heard, who heads the mosquito control program in St. Mary’s and Charles counties. Every year, his office starts a larvicide program to kill newly hatched mosquitoes while they are still in the water.
“We have people got out and check ditches” and other standing water, he said. That program begins in March. “We try to knock them down first that way.”
Trucks start spraying for mosquitoes the last week in June, he said. “We can’t get them all by larvicide.” Eight drivers hit 77 neighborhoods in St. Mary’s and 61 in Charles County at night once a week with an insecticide called permanone. Neighborhood residents pay 100 percent of the cost of this spraying.
This year the threat of Zika has more people interested in signing up for the spraying program. About 30 or 40 neighborhoods have asked about it, according to Greta Jones, who works in the mosquito control office, but many of them say they can’t afford it. About 60 individuals have checked about having their property sprayed, but that is even more expensive. The cost was $800 for one homeowner who chose to have it done.
Spraying usually runs until the end of September, but Zika could extend that longer. It takes a hard frost to kill mosquitoes, Heard said, and that sometimes doesn’t come in Southern Maryland until November.
Meanwhile, health mosquito control officials also emphasize to people how to protect against mosquito bites. That includes using screens on doors and windows and making sure any holes in those screens are repaired. The health department also recommends using an EPA-registered insect repellent with DEET, picaridin, IR3535, or oil of lemon eucalyptus or para-menthane-diol. For a list of EPA-registered insect repellents, visit www. epa.gov. These repellents are effective and safe when used as directed, Prochnow said.
There is an ongoing discussion in Maryland about how to respond to the Zika virus, she said. “Strategies are always changing,” she said. “We are learning so much more about this disease.”