The case reportedly involved a New York man who had vaginal intercourse with a non-pregnant woman in her twenties who happened to be at the beginning of her menstrual cycle — on the day she returned from travel to an area infected by the mosquito-borne virus.
"The man reported that he noticed no blood on his uncircumcised penis immediately after intercourse that could have been associated either with vaginal bleeding or with any open lesions on his genitals," the CDC said.
A week later, the man developed fever, joint pain, conjunctivitis and a rash. All previously reported cases of sexual transmission of Zika were of men to their sex partners.
Hoping to head off an epidemic in Pennsylvania before it begins, the state Department of Health announced it has begun distributing Zika prevention kits for pregnant women.
The kits contain mosquito repellent for skin and for treating clothing and shoes as well as tablets for killing mosquito larva in standing water. Also included are condoms to prevent sexual transmission, along with educational materials in both English and Spanish.
"Using the products in the Zika Prevention Kit can help protect you and your loved ones from the virus," Health Secretary Karen Murphy said in a news release.
A limited number of the Health Department kits will be available in up-coming days at a half-dozen locations in the Lehigh Valley, including the health bureaus of both Allentown and Bethlehem.
As of Monday, Pennsylvania had 40 confirmed cases of Zika, according to the state Department of Health. An additional 169 possible cases were awaiting test results.
Zika can cause microcephaly — or an abnormally small head — in babies born to mothers who were infected with the disease during pregnancy. It is a first-of-its-kind health threat. Never before have birth defects been linked to an illness spread by mosquitoes.
In Brazil, the epicenter of the current Zika outbreak, about 5,000 babies have been born with microcephaly.
According to the health department, pregnant should also consider staying indoors when mosquitoes are most active; wearing light-colored, lightweight, loose-fitting clothing that covers hands, arms, legs and other exposed skin; and sleeping in air-conditioned or screened rooms, or under a mosquito net when outdoors.
"In partnership with the Department of Health, we advise all Pennsylvanians to take precautions to reduce and control mosquito populations in their area and to take appropriate actions to protect themselves from mosquito bites," Acting Department of Environmental Protection Secretary Patrick McDonnell said. "DEP personnel and county partners are monitoring for the presence of mosquitoes that have the potential to transmit the Zika virus."
In the United States, 346 pregnant women have tested positive for Zika, and nine women have had babies with birth defects believed to be caused by the virus, according to the CDC. The lifetime cost of care for a microcephalic child could be between $1 million and $10 million, CDC Director Dr. Thomas Frieden said recently.
In most people, Zika has no symptoms. In others, the fever and other symptoms experienced by the man in New York are typical.
Zika also has been tied to two debilitating diseases that affect adults: Guillain-Barre syndrome and encephalomyelitis. With Guillain-Barre, the body's immune system attacks part of the peripheral nervous system, sometimes causing partial paralysis. Encephalomyelitis causes a temporary swelling of the spinal cord or brain, resulting in symptoms that resemble multiple sclerosis.
Thus far, Zika does not appear to have gained a foothold in the United States. Of the 1,306 confirmed domestic cases, all have been travel-related with the exception of 14 transmitted sexually and one acquired in a laboratory, according to the CDC.
Many health care experts, however, believe the virus could infect U.S. mosquito populations this summer. It is transmitted by at least one species of mosquito — the aedes aegypti, whose potential range, according to the CDC, includes southeastern Pennsylvania — and maybe by two species. The second -— the aedes albopictus, or Asian tiger — has a small but growing population in the Lehigh Valley.
The Obama administration has asked Congress to appropriate roughly $2 billion in Zika funding. However Congress, divided along party lines, adjourned Thursday for summer break without allocating money.
With or without intervention, the current Zika epidemic is likely to burn itself out like a wildfire, according to new research from a group of scientists who believe the epidemic's peak may already have already passed.
"The current epidemic is not containable; at best, interventions can mitigate its health impacts," the group, led by Imperial College London epidemiologist Neil M. Ferguson, wrote in the journal Science. "More optimistically, the natural dynamics of the epidemic are now likely to give a multiyear window to develop new interventions before further large-scale outbreaks occur."
At a slower rate and with seasonal ebb and flow, the virus' march across the Americas will likely grind to a halt, the group's epidemiological model suggests. After that, another Zika epidemic in the Americas would be unlikely for "at least a decade."