The Americas

Scientists are bewildered by Zika’s path across Latin America

By Dom Phillips, Nick Miroff

October 25, 2016 at 3:24 PM

Infants born with microcephaly and their family members in Pernambuco state in Brazil. (Felipe Dana/AP)

Nearly nine months after Zika was declared a global health emergency, the virus has infected at least 650,000 people in Latin America and the Caribbean, including tens of thousands of expectant mothers.

But to the great bewilderment of scientists, the epidemic has not produced the wave of fetal deformities so widely feared when the images of misshapen infants first emerged from Brazil.

Instead, Zika has left a puzzling and distinctly uneven pattern of damage across the Americas. According to the latest U.N. figures, of the 2,175 babies born in the past year with undersize heads or other congenital neurological damage linked to Zika, more than 75 percent have been clustered in a single region: northeastern Brazil.

The pattern is so confounding that health officials and scientists have turned their attention back to northeastern ­Brazil to understand why Zika’s toll has been so much heavier there. They suspect that other, underlying causes may be to blame, such as the presence of another ­mosquito-borne virus like chikungunya or dengue. Or that environmental, genetic or immunological factors combined with Zika to put mothers in the area at greater risk.

“We don’t believe that Zika is the only cause,” Fatima Marinho, director of the noncommunicable disease department at Brazil’s Ministry of Health, said in an interview.

Brazilian officials were bracing for a flood of fetal deformities as Zika spread this year to other regions of the country, Marinho said. However, “we are not seeing a big increase.”

Researchers and health officials remain cautious about the lower-than-expected numbers. The latest studies have found more evidence than ever that the virus can inflict severe damage on the developing infant brain, some of which may not be evident until later in childhood.

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Doctors confirmed the link between the Zika virus and microcephaly in April. While the most visible sign of microcephaly is the small size of the head, its actually inside the brain where the most damage occurs. (The Washington Post)

But researchers so far have learned a lot more about Zika’s potential to do harm than its likelihood of doing so.

Scientists at the U.S. Centers for Disease Control and Prevention are closely watching Puerto Rico, which has reported more than 26,800 cases of Zika. More than 7,000 pregnant women could be infected by the end of the year, according to the CDC.

But although the outbreak has spread this year to more than 50 nations and territories across the Western Hemisphere, U.N. data shows just 142 cases of congenital birth defects linked to Zika so far outside Brazil.

In Colombia, praised for some of the most rigorous standards for detecting and monitoring Zika, the government has tallied more than 104,000 Zika cases, including nearly 20,000 pregnant women. It has the ­second-highest number of Zika infections in the world after Brazil.

But so far, Colombia has had just 46 babies born with congenital nervous system damage linked to Zika. And the number of new Zika cases in Colombia has fallen so sharply that the government in July declared the epidemic over, saying the virus will remain a threat but no longer spread rampantly.

Colombia is investigating 332 more cases of birth defects for a possible Zika link, but health officials there had been prepared for many more.

“Our focus on Zika has changed,” said Ernesto Marques, an epidemiologist at the University of Pittsburgh who is working on a project to develop a vaccine for the virus.

Marques is from Recife, the city in northern Brazil hit hardest by the Zika outbreak, and he was part of the team that first identified the virus as a possible culprit when deformed infants began showing up “almost every day” in Recife’s maternity wards at this time last year.

At the time, Marques said scientists were focused on identifying Zika as a “causal agent” for the sudden increase in birth defects, especially microcephaly, in which babies are born with undersize heads and often calcified brain tissue.

“Now we’ve settled on Zika as the smoking gun, but we don’t know who pulled the trigger,” said Marques, speaking from Recife, where he is working with government researchers.

One of the leading theories, said Marques, is that northeastern Brazil’s last dengue outbreak was in 2003 — relatively long ago — so perhaps mothers in the area had relatively fewer antibodies to cope with Zika, which is spread by the same mosquito.

“Sexual habits and hygiene may also play a role,” he said, explaining that researchers are looking at whether sexual transmission can infect the uterus and placenta with the virus, potentially exposing the fetus to elevated risk.

“We suspect the villain has an accomplice, but we don’t know who it is,” Marques said.

Tatiane holds her nephew Arthur Conceicao, who was born last year with microcephaly, during his birthday party in Recife, Pernambuco state, Brazil. (AP Photo/Felipe Dana) (Felipe Dana/AP)

Many question marks

Researchers caution that it will take years to fully identify the dangers Zika poses to babies’ brains, and microcephaly is just one threat from the virus. A Zika infection poses the greatest danger toward the end of the mother’s first trimester of pregnancy, and its harmful effects on fetal development may not be apparent at birth or manifest themselves until later in childhood.

Marcos Espinal, the director of communicable diseases and health analysis at the Pan American Health Organization, said U.N. health officials were right to put the world on high alert earlier this year because so little was known about Zika.

“If you don’t know about something, you better take preventative measures to minimize the risks,” Espinal said. “So maybe the fact that we don’t have a lot of microcephaly means that we were doing our jobs” and helped women avoid infection.

At the peak of Zika alarm earlier this year, several Latin American countries urged women to delay pregnancy. El Salvador’s government recommended waiting two years. The widespread anxieties produced by the outbreak may have led to an increase in abortions in Latin America, a region where the procedure is widely banned. Anecdotal evidence suggests more women have been quietly terminating pregnancies over worries that their babies might be deformed.

This may also help explain the relatively low number of babies born with Zika-related birth defects outside northeast Brazil.

“It is very difficult to work out truly what is going on,” said Oliver Brady, an epidemiologist at the London School of Hygiene and Tropical Medicine who has been working with the Brazilian government on Zika.

Until last year, Brazil reported about 150 cases annually of microcephaly, a condition that can also be caused by diseases like herpes and syphilis. Claudio Maierovitch, a former senior Brazilian health official responsible for monitoring Zika when the epidemic started, said that the figure was probably an undercount and that around 500 cases of microcephaly a year pre-Zika would be a more accurate number.

When the microcephaly outbreak was first identified in Brazil, spooked health officials erred in the other direction and overdiagnosed the condition. Eventually, nearly 5,000 newborns who had been diagnosed with possible microcephaly turned out to be fine, according to Marinho, the Brazilian health official.

But that still leaves at least 2,000 instances of Zika-related birth defects in the country, with an additional 3,000 cases under investigation.

A big problem in determining whether Brazil has a higher rate of Zika-related birth defects is that no one is sure how many people caught the virus in 2015, when it was little known and widely confused with dengue.

“The fact is we don’t have any idea how many cases there were,” said Maierovitch, meaning it’s possible Brazil’s birth-defect totals could simply be a reflection of a Zika outbreak that was far more pervasive than anywhere else.

Lucas Matheus, who was born with microcephaly, during his physical therapy session at the UPAE hospital in Caruaru, Pernambuco state, Brazil. (AP Photo/Felipe Dana) (Felipe Dana/AP)

An eye on U.S. territory

Puerto Rico is the next laboratory for understanding Zika. CDC researchers are watching for Zika-related birth defects on the island, but the mainland United States appears to have averted a major outbreak so far.

The vast majority of cases the CDC has counted were attributed to infections acquired abroad or through sexual transmission, though mosquitoes have spread the virus in a few neighborhoods in and around Miami. Experts have warned, however, that local mosquito-driven outbreaks may be occurring in other parts of the country, particularly in states on the Gulf of Mexico. An estimated 80 percent of people infected with the virus don’t have symptoms and don’t realize they have Zika.

Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine, said Congress’s failure to approve Zika funding this year means there was no effective way to accurately count how many people were infected.

“We’ll have to hold our breath to see what happens in labor and delivery suites in a few months,” he said. “That’s the only way we’ll know whether we’ve dodged a bullet.”

A health ministry worker fumigates a house to kill mosquitoes during a campaign to prevent Zika in Managua, Nicaragua. (Oswaldo Rivas/Reuters)
A technician inspects the pupae of genetically modified Aedes aegypti mosquitoes at the Oxitec factory in Piracicaba, Brazil. (Paulo Whitaker/Reuters)
Aileen Marty, professor of infectious diseases at Florida International University, explains the use of insect repellent towelettes in Miami, where kits and information about Zika are being distributed in the city's poorest neighborhoods. (Alan Diaz/AP)
Nelson Tejeda, a Miami-Dade County mosquito control inspector, uses a pesticide sprayer. (Joe Raedle/Getty Images)
A city worker fumigates the area to control the spread of mosquitoes at a temple in Bangkok. (Chaiwat Subprasom/Reuters)
A Buddhist monk covers his nose as a city worker fumigates the area to control the spread of mosquitoes at a temple in Bangkok. (Chaiwat Subprasom/Reuters)
A Ministry of Health worker fumigates the area to control mosquitoes in Kuala Lumpur, Malaysia. (Joshua Paul/AP)
A Florida Department of Health employee processes a urine sample to test for the Zika virus in Miami Beach. (Lynne Sladky/AP)
Vince Iuliano, right, gives a urine sample to a Florida Department of Health workers as they provide a free Zika test at a temporary clinic set up at the Miami Beach Police Department. (Joe Raedle/Getty Images)
Residents of an impoverished colony watch as municipal workers fumigate to control the spread of mosquito-borne diseases in New Delhi. (Manish Swarup/AP)
Municipal worker Sunil Chauhan prepares to fumigate an area in New Delhi. (Manish Swarup/AP)
Nurses set up a mosquito tent over a hospital bed, as part of a precautionary protocol for patients who are infected by Zika, at Farrer Park Hospital in Singapore. (Edgar Su/Reuters)
A pest control worker checks for mosquitoes breeding in a drainage duct at Bedok North housing estate in Singapore. (Roslan Rahman/AFP/Getty Images)
An exterminator fumigates a common area next to an apartment block in the Bedok North district of Singapore. (Wallace Woon/European Pressphoto Agency)
Robert Murillo gets help putting on his spraying apparatus as San Diego County officials hand-spray a two-block area to help prevent the mosquito-borne transmission of the Zika virus. (Earnie Grafton/Reuters)
A nurse bottle feeds a newborn baby afflicted with microcephaly at a maternity ward of the University Hospital in Tegucigalpa, Honduras. (Fernando Antonio/AP)
Aubry Lines of the Salt Lake City Mosquito Abatement District checks for mosquito larvae. Mosquito abatement teams in Salt Lake City are stepping up efforts to trap and test mosquitoes and kill larvae after the discovery of a unique Zika case that has health investigators trying to figure out how the man got the virus. (Rick Bowmer/AP)
Municipal health workers and a truck fumigate on the northern outskirts of Gwangju, South Korea. The effort to eliminate possible mosquito breeding grounds came a day after South Korea reported its first case of the Zika virus. (Gwangju Northern Ward / Handout/European Pressphoto Agency)
Workers from a disinfection service company sanitize the floor of Incheon International Airport in South Korea. (Ha Sa-hyun/Yonhap via Reuters)
Researchers from the Uganda Virus Research Institute sort samples of mosquitoes collected from the Zika Forest in Entebbe, Uganda. In the forest, near Lake Victoria, mosquitoes carrying the Zika virus buzz amid the local community. (James Akena/Reuters)
A man covers his face as a Cuban military reservist fumigates a house as part of preventive measures against the Zika virus and other mosquito-borne diseases in Havana. (Ivan Alvarado/Reuters)
A view inside a house as a Cuban military reservist fumigates it as part of preventive measures against the Zika virus and other mosquito-borne diseases in Havana. (Ivan Alvarado/Reuters)
A woman smokes while a Cuban military reservist fumigates inside a home as part of the preventive measures against the Zika virus and other mosquito-borne diseases in Havana. (Ueslei Marcelino/Reuters)
Lara, who is just under 3 months old and was born with microcephaly, is examined by a neurologist at the Pedro I hospital in Campina Grande, Brazil. (Felipe Dana/AP)
Soldiers inspect a home built under a rock during an operation to combat Aedes aegypti mosquitoes, which transmit the Zika virus, in Monteiro, Brazil. (Felipe Dana/AP)
Lissette Salas, a patient in Caracas, Venezuela, with Guillain-Barr syndrome, has been in the hospital for a week after showing symptoms of paralysis in her body. (Alejandro Cegarra/for The Washington Post)
A woman waits for be treated in the Hospital Vargas emergency room in Caracas. (Alejandro Cegarra/for The Washington Post)
A doctor runs a test to discard diseases that may be confused with Zika at a Hospital Vargas laboratory. (Alejandro Cegarra/for The Washington Post)
Aedes aegypti mosquitoes, which transmit dengue fever and Zika virus, are pictured in a jar at the International Atomic Energy Agencys Insect Pest Control Laboratory in Seibersdorf, Austria. (Christian Bruna/European Pressphoto Agency)
Boxes with mosquitoes are seen inside the International Atomic Energy Agency. (Leonhard Foeger/Reuters)
Aedes aegypti mosquitoes are seen at the IAEA. (Leonhard Foeger/Reuters)
Group leader Masafumi Inoue of the Agency for Science Technology and Researchs (A*STAR) Experimental Therapeutics Centre in Singapore holds up a sample to be tested with the Zika virus diagnostic test kit. (Edgar Su/Reuters)
Daniele Santos, 29, holds her son Juan Pedro, who is 2 months old and was born with microcephaly, after bathing him at their house in Recife, Brazil. (Nacho Doce/Reuters)
Santos combs her sons hair. (Nacho Doce/Reuters)
A health worker fumigates the cemetery of Surco in Lima, Peru, to prevent the Zika virus and other mosquito-borne diseases. (Mariana Bazo/Reuters)
Protected by a mosquito net, Iris Ramona Gonzalez recovers from a bout of dengue fever at a hospital in Luque, Paraguay. (Jorge Saenz/AP)
A Guatemalan Health Ministry employee eliminates potential breeding places of Aedes aegypti mosquitoes, vectors of the dengue, Zika and Chikungunya viruses, at La Comuna II neighborhood in Guatemala City. (Johan Ordonez/AFP/Getty Images)
Health Ministry employees fumigate against the Zika virus in Guatemala City. (Johan Ordonez/AFP/Getty Images)
A Mexican Health Secretary worker fumigates at a cemetery in Oaxaca, Mexico. (Mario Arturo Martinez/European Pressphoto Agency)
Brazilian army soldiers distribute fliers with information on how to combat the Aedes aegypti during the Burial of the Mosquito carnival block parade in Olinda, Brazil. (Felipe Dana/AP)
Health Ministry worker Carlos Lopez shows larvae of mosquitoes he found during a fumigation campaign in Guatemala City. (Moises Castillo/AP)
Spraying equipment in the back of a pickup truck from the Chacao municipality is used to fumigate the grounds of a school to eradicate the mosquitoes in Caracas, Venezuela. (Wilfredo Riera/Bloomberg News)
An employee of the municipality of Chacao fumigates a church in Caracas, Venezuela. (Miguel Gutierrez/European Pressphoto Agency)
A child tests a racket zapper, which can be used to kill mosquitoes that might carry Zika, dengue and Chikungunya viruses in San Salvador. (Jose Cabezas/Reuters)
Mara Luiza Ribeiro Rosa, 32, a beautician who is nine months pregnant with her third daughter, said she made precautions around her home to fight against mosquitoes and will use a mosquito net on the crib for the baby. (Lianne Milton/Panos Pictures/for The Washington Post)
Cristiane Facio, 40, a mother of two, checks a baby at Hospital Universitario Clementino Fraga Filho in Rio de Janeiro. Facio tested positive for the Zika virus in her third trimester. However, after an ultrasound, there were no symptoms of microcephaly in the baby. (Lianne Milton/Panos Pictures/for The Washington Post)
Repellents are displayed for sale at a store in Sao Paulo, Brazil. (Paulo Whitaker/Reuters)
A municipal worker fumigates inside a building to help control the spread of the mosquito-borne Zika virus in Caracas, Venezuela. (Marco Bello/Reuters)
A health agent conducts an inspection for the Aedes aegypti mosquito inside a house in Rio de Janeiro. The inspection was part of efforts to prevent the spread of the Zika virus. (Pilar Olivares/Reuters)
A health agent shows a chemical compound used to kill mosquito larvae during the inspection of a house in Rio de Janeiro. (Pilar Olivares/Reuters)
From left, health officials Daniel Soranz, Joao Grangeiro and Alexandre Chieppe attend a news conference in Rio de Janeiro. Olympics organizers said they are concerned about the Zika virus in Brazil but are confident the problem will be cleared up before the Games begin. (Buda Mendes/Getty Images)
Health workers hand out mosquito repellent to a pregnant woman during a campaign to fight the spread of Zika virus in Soledad municipality near Barranquilla, Colombia. (Handout/Reuters)
Municipal workers trim vegetation as part of efforts to prevent the spread of the Zika virus in Tegucigalpa, Honduras. (Jorge Cabrera/Reuters)
Fathers and children crowd a hospital in Tegucigalpa. Honduran President Juan Orlando Hernndez declared the country to be on a state of alert because of the Zika virus, which has killed a person and infected 1,000. (Orlando Sierra/AFP/Getty Images)
Honduran Health Ministry personnel fumigate a classroom in Tegucigalpa. (Orlando Sierra/AFP/Getty Images)
Residents wait outside a house being fumigated by health workers on the outskirts of Lima, Peru. (Mariana Bazo/Reuters)
Colombian women at the transport terminal in Bogota listen as a health worker distributes information on how to prevent the spread of the Zika virus. (John Vizcaino/Reuters)
A garbage collector removes potential breeding grounds for the Aedes aegypti mosquito, which transmits the Zika virus, in Cucuta, Colombia. (Schneyder Mendoza/AFP/Getty Images)
A health worker empties a makeshift flower vase while searching for mosquito larvae near Lima, Peru. (Mariana Bazo/Reuters)
A Health Ministry worker fumigates the Oriental Market in Managua, Nicaragua. (Inti Ocon/AP)
Gisele Felix, who is 5 months pregnant, applies repellent on her arm at her home in Rio de Janeiro. (Pilar Olivares/Reuters)
A San Salvador city worker helps Simon Jose Valentin, 94, leave his home while it is being fumigated. (Salvador Melendez/AP)
Municipal workers wait before spraying insecticide at Sambodrome in Rio de Janeiro. (Pilar Olivares/Reuters)
Dominican air force personnel fumigate various locations in Santo Domingo to try to contain the Aedes aegypti mosquito. (Erika Santelices/AFP/Getty Images)
Children flee as an area is fumigated in Santo Domingo, Dominican Republic. (Erika Santelices/AFP/Getty Images)
Photo Gallery: How countries are combating the Zika virus

Lena H. Sun in Washington contributed to this report.

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Related: Today’s coverage from Post correspondents around the world

Dom Phillips is The Post's correspondent in Rio de Janeiro. He has previously written for The Times, Guardian and Sunday Times.

Nick Miroff is a Latin America correspondent for The Post, roaming from the U.S.-Mexico borderlands to South America’s southern cone. He has been a staff writer since 2006.

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