By Daniel Chang

Miami Herald

How Zika made it from Uganda to the U.S.

Beginning with the first incidence occurring in monkeys in Uganda in 1947, the Zika virus has trickled across the globe until the recent outbreak in Brazil and many other Latin American and Caribbean countries and territories. A look at the origins of Zika:

1. Uganda — 1947

Medical researchers first identified the Zika virus in 1947 in rhesus monkeys of the Zika Forest in Uganda. Testing data retroactively gathered in 1952 detected Zika in humans for the first time in Uganda, Tanzania, Nigeria and Senegal. The first real-time detection in a human occurred in Nigeria in 1954.

2. Island of Yap — 2007

Faced with several residents experiencing denguelike symptoms, physicians in Yap, a Pacific island just north of Australia, sent samples to the CDC for testing. Forty-nine cases were eventually confirmed, the virus’ first major outbreak.

3. Colorado — 2008

The first sexually transmitted case originated in northern Colorado in 2008. The wife of a Colorado State University biologist experienced symptoms after having sex with him. He had been in Senegal studying malaria and was bitten by mosquitoes. When he returned home, he didn’t realize he had contracted the virus. Blood tests confirmed the virus for both.

4. French Polynesia, Pacific Islands — 2013-14

Health professionals confirmed 294 incidences in the islands of French Polynesia, after a family of three experienced symptoms associated with the virus — mild fever, headache, joint pain and pink eye. By 2014, Zika had jumped to other islands, including New Caledonia and Cook Islands in the South Pacific and Easter Island, off the coast of Chile, the first cases in the Western Hemisphere.

5. Brazil — 2015

The Pan American Health Organization announced the first cases of Zika in Brazil in May 2015 after noticing a spike in severe congenital birth defects caused by microcephaly. There are theories that major sporting events hosted by Brazil — the Va’a World Sprint Championship in Rio de Janeiro and the World Cup, both in 2014 — ushered in the virus. However, scientists can’t point to one or the other with certainty. Dr. Paola Lichtenberg, director of tropical diseases at UHealth, said, “We just know for sure that the outbreak in Brazil can be traced back to French Polynesia.”

6. Texas — Feb. 2, 2016

The second case of human-to-human transmission in the U.S. was confirmed in Dallas. Texas health officials reported a Dallas resident contracted Zika after having sex with someone who had recently returned from Venezuela.

Sources: World Health Organization; Dr. Paola Lichtenberger, director of tropical medicine, UHealth; U.S. National Library of Medicine National Institute of Health; Centers for Disease Control and Prevention

MIAMI — In 2007, physicians working on a remote island in the western Pacific Ocean reported an outbreak of an illness with flu-like symptoms similar to dengue fever, a debilitating viral disease transmitted by mosquitoes and well documented since the 18th century.

But the illness observed by doctors on Yap Island in Micronesia seemed different than dengue — with sudden onset of rash, joint pain or red eyes, and no cases of hemorrhagic fever.

Patient blood samples sent to the U.S. Centers for Disease Control and Prevention would later confirm the first recorded outbreak of what was then an obscure pathogen.

“We didn’t have any idea that it was Zika virus,” said Lt. Col. Mark Duffy of the U.S. Air Force, one of the lead physician researchers dispatched to investigate the mystery illness in June 2007. “There was just a paucity of literature that was out there.”

Until then, Zika had been something of a sleeper virus. Only 14 cases of human Zika disease had been documented prior to 2007, and all of them were in Africa and Asia, according to an article on the Yap Island upsurge published in the New England Journal of Medicine in 2009. Researchers identified 49 confirmed cases of Zika and estimated 73 percent of the population had been infected with the virus.

Nearly nine years after the first Zika outbreak was documented by Duffy and a team of disease detectives — a collaborative effort involving the CDC, the World Health Organization and the nonprofit Pasteur Institute — the virus has spread rapidly across South America and the Caribbean, triggering warnings of a global health threat.

But physicians and public health officials still lack the basic scientific research to understand precisely how Zika spreads or to establish a causal connection with a concurrent spike in microcephaly, a congenital birth defect, and other neurological disorders following outbreaks of the virus in Brazil in 2015 and in French Polynesia in 2014.

There is no tool available that allows physicians to diagnose the Zika virus in the field, limiting their ability to quickly identify the disease and take action. There is no vaccine or specific medical treatment for the virus’ symptoms, which affect only 1 in 5 infected people. And it’s unclear whether the virus is transmitted only by mosquitoes, or perhaps also through sexual contact, as health officials believe occurred in Texas this year.

“We’re all steep on this dreadful learning curve,” said Elizabeth Talbot, a physician and infectious diseases expert at Dartmouth College’s Geisel School of Medicine. “There are a lot of negatives, and there are a lot of unknowns right now.”

Those unknowns, particularly the suspected link between the virus and birth defects, are precisely the reasons cited by the WHO’s Emergency Committee for declaring an international emergency for Zika on Feb. 1.

Catherine Spong, a physician-scientist and acting director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, said the most important unanswered question is whether Zika virus is causing birth defects and other neurological disorders.

“If in fact it is,” Spong said, “then we need to work through exactly when that happens and how can we prevent that.”

Duffy, the physician who investigated the Zika outbreak on Yap Island in 2007, said the team of scientists spent a month in the field studying the transmission and symptoms of the disease.

In that time, he said, the team made several important observations, including the determination that only about 1 in 5 people infected with the virus show symptoms.

Duffy surmised the Zika virus likely arrived on the remote island via an infected monkey, an infected person or a mosquito carried aboard a cargo container or airplane.

The team determined about 75 percent of the island’s population had been infected with Zika during the outbreak, he said, and they were the first to characterize the disease’s symptoms in a broad population.

But, Duffy said, “There wasn’t any indication at that point about the fetal anomalies or Guillain-Barre syndrome,” a neurological disorder often associated with viral infections.

The only way to prove a causal link between the virus and any of the suspected outcomes is through epidemiological research, including cohort and case-control studies, which then would require further research for prevention and treatment.

Scientific efforts, including case investigations and ecological research, already are underway to close the know­ledge gap on Zika, the WHO reported.

President Barack Obama asked Congress for $1.8 billion in emergency funding Tuesday to combat the virus through mosquito control, vaccine research, education and improving health care for low-income pregnant women.

The CDC also is responding to state requests for help, sending, for instance, 950 Zika antibody tests to Florida this week at the request of Gov. Rick Scott — in addition to 475 tests sent last week. Sixteen cases have been identified in Florida so far, all acquired outside the country and none involving pregnant women.

Talbot, the infectious disease expert at Dartmouth, who also is New Hampshire’s deputy state epidemiologist, said “very active investigations” into a causal link between Zika and birth defects are underway now. But, she said, the scientific community shouldn’t expect to arrive at definitive conclusions for three to six months.

Until then, she said, people worried about Zika virus should listen to what is known about transmission of the disease and its symptoms.

“Pregnant women should try to postpone travel to the affected regions,” she said. “We have confidence in that recommendation.”

Talbot added that practical advice can go a long way, including the use of insect repellents DEET or Permethrin in clothing and removing containers and places where mosquitoes breed.

“Maybe they’re not always simple,” she said, “but they are effective.”