Cases of Zika infection have dropped significantly in Georgia and across the United States, public health officials say.

Despite the decrease, the Atlanta-based CDC emphasizes that Zika continues to be a public health threat.

Zika is a tropical, mosquito-borne virus that has occasionally ranged into the southernmost parts of the U.S. but more often has affected Americans traveling to tropical regions. In many adults, it causes no symptoms or deceptively mild symptoms, but if a pregnant woman is infected, her baby may have serious birth defects.

In the United States, there have been 215 symptomatic Zika virus disease cases reported as of Aug. 23 this year, down from 5,102 cases in all of 2016. The number of cases also is way down in tropical U.S. territories, including Puerto Rico, where Zika was prevalent last year.

Public health officials in Georgia say the state has identified just five cases of travel-related Zika infections so far this year, down from 114 last year.

The Georgia agency's interim commissioner, Dr. Patrick O'Neal, told GHN recently that "we now have reached a point where a significant percentage of the population in the countries where Zika was so endemic have already contracted the virus and have immunity to it. So many people have immunity."

"Eighty percent of people with Zika have no symptoms," O'Neal said. "So the population in those countries are reasonably immune to Zika. So we are not going to see the amount of transmittal of disease that we saw before."

In the Miami-Dade County area of Florida, where many Zika cases emerged last year, NPR reported in June that health officials hadn't investigated a new Zika case for more than 45 days. The CDC is no longer recommending that pregnant women avoid the region.

Also in June, Puerto Rico declared its Zika epidemic over, saying transmission of the virus on the island has fallen to relatively low levels, STAT reported.

This month, the CDC has decreased the number of Zika response personnel in the Emergency Operations Center, officially transitioning the Zika response from a Level 1 to a Level 2 earlier in August, then to a Level 3 activation as of Aug. 29.

Danger has not disappeared

Although there are certainly fewer cases now, a CDC spokesman told Georgia Health News, "A decrease in activation level does not mean that a disease threat has lessened in importance or that people are no longer at risk for Zika."

Anywhere Zika is active, the threat to pregnant woman remains very real. Of the 250 pregnant women who had confirmed Zika infection last year, 24 - or about 1 in 10 - had a fetus or baby with Zika-related birth defects, according to an April report from the CDC.

Public health officials in Georgia said in January that the state documented one Zika-related birth defect here.

The CDC spokesman, Benjamin Haynes, told GHN: "CDC will continue its work focusing on protecting pregnant women and their infants, including providing support to health care providers as they counsel women infected during pregnancy. CDC will also support planning at the federal, state and local levels for clinical, public health and other services needed by families affected by Zika."

Mystery added to the initial fear

When Zika virus first emerged as a sensation in the news in 2015, fear of the unknown rippled across the world. An endless stream of questions surfaced: Who is at risk? Where is it spreading? How does it work?

Scientists and public health officials banded together to study the virus and answer the most urgent questions. Although it had long been known that the Zika virus was transmitted by Aedes species mosquitoes (like related viruses dengue and chikungunya), much was still unknown about Zika transmission and the long-term effects of the disease.

By April 2016, scientists confirmed that the Zika virus could be transmitted from a mother to her baby during pregnancy. The CDC then told the public that the virus could cause birth defects such as microcephaly, a serious condition characterized by abnormally small heads and incomplete brain development.

What we know about Zika

As it stands now, the CDC reports that the Zika virus can be transmitted through mosquito bites, from an infected pregnant mother to her fetus, but also through sexual intercourse and potentially through blood transfusion.

The symptoms of Zika disease, where they are noticeable, are fairly nondescript, often including joint pain, fever, headache, rash and red eyes that can last for up to a week. For most infected individuals, minor disease is managed by the immune system, and the individual is likely to be protected from future infection.

Sexual transmission of Zika occurs because some people infected by mosquito bites don't feel ill and go about their normal activities. But however the virus is transmitted, Zika and pregnancy are a dangerous mix.

Zika infection during pregnancy can cause stillbirth or miscarriage. In some cases, Zika has been linked to an increased risk for Guillain-Barre syndrome, an autoimmune disorder in which paralysis and nerve damage are characteristic.

Zika prevention

"We still have no vaccine or therapeutics for individuals that are infected with Zika virus," Dr. Mehul Suthar, a Zika expert at Emory, told GHN.

As a result, the CDC recommends preventing disease by protecting yourself and your family from mosquito bites. The best forms of protection are utilizing long-sleeved shirts and long pants, Environmental Protection Agency-registered insect repellants and mosquito netting and staying in air conditioned or screened buildings. Additionally, the CDC recommends condom usage to prevent sexual transmission of the virus.

A health care professional can conduct a blood or urine test to confirm the presence of Zika virus. Although there is not a specific treatment or vaccine for Zika disease, the CDC recommends drinking fluids, getting rest, treating fever and pain with acetaminophen instead of aspirin and checking in with your health care provider before treating with additional medication.

Areas at risk for Zika infection include Mexico, Cuba, most of South America, and tropical and subtropical regions in African countries.