Four additional cases suspected to be locally transmitted Zika virus have been identified in Cameron County, Texas, according to state and local health departments. The state's first likely case of locally transmitted Zika virus was announced November 28. The new cases are in "very close proximity to the first case," according to a statement. None of the cases is in pregnant women. Testing in the area is continuing.
Texas is the second state in the continental United States
to confirm a locally transmitted case of the Zika virus, state and federal health officials said. Lab results confirmed the virus in a non-pregnant female resident of Brownsville in November. She has not traveled to an area where the virus is circulating and has no other known exposure to the virus that would have put her at risk for infection.
State health officials say that travel across the border is frequent in the area. Zika transmission has been reported in multiple communities on the Mexican side of the border.
November 22, 2016: Zika babies born without microcephaly may not be in the clear
of 13 Brazilian babies born with congenital Zika virus infection but not microcephaly found that 11 of them (85%) developed the neurological condition within their first year of life. The babies had a normal head circumference at birth and were therefore thought to be free of the sometimes-devastating condition. The researchers say this emphasizes the need for babies born to Zika-infected mothers to be followed carefully for the first 12 months of life.
November 22, 2016: North Miami Beach no longer active Zika zone
An area of North Miami Beach, Florida, is no longer "an area of active Zika transmission," the CDC said.
No new cases of locally transmitted Zika virus have been reported in the 4.5-square-mile area for at least 45 days, the agency said, and therefore it is now a "cautionary area" along with all of Miami-Dade County.
There are still two active transmission areas in Miami: a 1½-square mile area of South Miami Beach and a 1-square-mile area of Little River, the Florida Department of Health said.
November 20, 2016: Florida Keys to begin using GMO mosquitoes
As new locally transmitted cases of the Zika virus continue to be reported daily by Florida health officials daily, residents of the Keys have given the OK to release genetically modified mosquitoes in an experimental effort to stop the Aedes aegypti, which carries Zika and other viruses. The GMO mosquitoes create a protein that interferes with the cell activity in disease-carrying female mosquitoes, killing their offspring before they reach adulthood, which is when they begin infecting humans with their bite.
Having been given the go-ahead from the FDA in August
, British company Oxitec plans to begin the trial early next year and has said that if all goes well, Miami could get the mosquitoes later in the year.
November 18, 2016: WHO declares end to public health emergency
The Zika virus outbreak and related clusters of microcephaly are no longer a public health emergency of international concern, the World Health Organization said, ending the declaration it made in February. "We are not downgrading the importance of Zika. By placing this as a long-term program of work, we are saying Zika is here to stay," said Dr. David Heymann, chairman of the emergency committee on Zika virus and microcephaly, which made the announcement.
September 28, 2016: Federal Zika emergency funding bill passed
Congress approves a bill that designates $1.1 billion in federal money to fight Zika. Though short of the $1.9 billion requested in February, this funding is welcomed by many organizations and experts working to combat the virus. According to the House Appropriations Committee, $476 million will go to the CDC, $230 million will go to the National Institutes of Health, and $141 million will be designated for local assistance at the state and county level.
September 19, 2016: Miami neighborhood declared Zika-free
Florida Gov. Rick Scott and the Centers for Disease Control announce the lifting of a ban on travel to the small Miami neighborhood of Wynwood, saying that aggressive mosquito-control efforts have been successful in reducing the population of Zika-carrying mosquitoes. Wynwood was the subject of a historic ban on domestic travel when, on August 1, the CDC told pregnant women not to travel
to the 1-square-mile area of active Zika transmission.
However, just two days earlier, on September 17, Florida officials warned that a Zika transmission zone in Miami Beach has tripled in size
August 12, 2016: Public health emergency declared in Puerto Rico as Zika cases surpass 10,000
The Puerto Rico Department of Health announces that there have been 10,690 cases of the Zika virus confirmed, including 1,035 pregnant women. The Department of Health and Human Services declared a public health emergency there at the request of the governor. Secretary Sylvia Burwell said efforts are underway to fight the virus with a priority on protecting pregnant women.
August 11, 2016: Agency redirects money to fight Zika
Burwell is redirecting $81 million from elsewhere in the department to continue efforts to fight the Zika virus. She said in a letter to House Minority Leader Nancy Pelosi that she was exercising her authority to transfer $34 million from within the National Institutes of Health and $47 million from the Biomedical Advanced Research and Development Authority to keep "Zika-related activities" going. Without that, she said, the unused Ebola money they have been using since April will run out by the end of August and prohibit phase II of the Zika vaccine trial.
August 10, 2016: Virus found in semen six months after exposure
The Zika virus was found in the semen of two Italian men at least six months after they were exposed to the virus in Haiti. The cases are published online
by the European Center for Disease Prevention and Control. In one case, "persistent shedding" of the virus was found in semen for six months after the man returned. In the other, the virus was found in semen six months after his symptoms began. Previously, researchers had found the virus in semen as long as three months after exposure.
August 9, 2016: Zika may cause joint problems in babies
Babies born to mothers who were infected with the Zika virus are also developing joint deformities, particularly in their arms and legs, according to a study
published in the medical journal BMJ. Researchers in Brazil detail seven instances of the condition, called arthrogryposis, and say the problem is not orthopedic in that scans of the joints and tissues did not reveal anything. Therefore, they conclude it is a neurological problem but recommend that these babies be seen by an orthopedic specialist. More research is needed, but this adds to the evidence that Zika-related birth defects are not limited to microcephaly.
August 2, 2016: Human clinical trials begin for first potential Zika vaccines
The National Institute of Allergy and Infectious Diseases begins infecting healthy volunteers with an experimental DNA-based Zika vaccine. The research team hopes to enroll 80 volunteers between the ages of 18 and 35 at three locations. Participants will be followed for 44 weeks after receiving the vaccine at various intervals for 20 weeks.
A few days earlier, Inovio Pharmaceuticals began its own clinical
trial for a different potential Zika vaccine among healthy volunteers in Miami. That trial will include 40 healthy volunteers.
August 1, 2016: CDC issues historic travel warning in US
In an unprecedented move, the US Centers for Disease Control and Prevention warned pregnant women to steer clear of the Wynwood neighborhood in downtown Miami. This is the area where at least 15 people have been infected with the Zika virus by local mosquitoes carrying the disease.
July 29, 2016: Health officials confirm local mosquito transmission in the US
Florida health officials say four individuals in Miami-Dade and Broward counties were infected with the Zika virus by local mosquitoes. These are the first known cases of the virus being transmitted by mosquitoes in the continental United States.
"As we anticipated, Zika is here," said Dr. Tom Frieden, director of the CDC.
Officials believe that the local transmission is confined to a small area north of downtown Miami and that transmission occurred in early July.
July 21, 2016: Zika virus found in common Culex mosquito in Brazil
Researchers at Brazil's Fiocruz research institute announce that they have found the Zika virus in some Culex mosquitoes in Recife, a coastal city that has been labeled as the "hot zone" for the virus. Culex mosquitoes are sometimes called common house mosquitoes. The presence of the virus in these mosquitoes alone does not mean they can transmit the virus. Experts maintain that Aedes mosquitoes are the known vector.
July 18, 2016: Health officials investigate how family member of person who died of Zika became infected
A family member of an elderly Utah man who died from Zika-related illness
in June is infected with the virus, the Utah Department of Health said
. The 38-year-old man
had not traveled to an area where the virus is circulating and has not had sexual relations with anyone who has. Zika-carrying Aedes aegypti and Aedes albopictus mosquitoes do not live in Utah, although officials are looking for them or any other mosquito carrying the virus. Other relatives and health care workers who treated the deceased individual are also being screened for the virus. According to the CDC
, the person who died had "uniquely high amounts of virus -- more than 100,000 times higher than seen in other samples of infected people -- in his blood." A later report
found that the man could have become infected from the sweat or tears of his family member.
July 15, 2016: Female-to-male sexual transmission of Zika reported
The CDC reports the first known case of a woman with the Zika virus infecting her male sexual partner with the virus after they had unprotected vaginal intercourse. "This is the first documented case of sexual transmission of Zika from a woman to her sex partner and adds to the growing body of knowledge about the sexual transmission of Zika," the agency said.
All previous reported cases of sexual transmission of Zika have been transmitted by a man to his sexual partner.
The CDC said it was updating recommendations to protect against sexual transmission of the virus after travel to those who could become infected by a female.
July 8, 2016: Health officials report first Zika-related death in the continental US
Utah health officials report that a 73-year-old man who died in June was the first Zika-related death in the continental United States. Lab results confirming the unidentified individual was infected with the virus were not available until after the person died. The Utah resident was immunocompromised due to prostate cancer. He was infected with the virus while traveling to Mexico, where the virus is circulating.
June 16, 2016: CDC reports six Zika-infected babies in the US
The CDC says it will begin reporting outcomes of babies born to Zika-infected pregnant women
. In doing so, it reported that three babies have been born with birth defects in the United States. It also said three pregnancy losses (including miscarriage, stillbirths and terminations) had occurred. All six of these cases are among infants infected with the virus before or during birth.
June 15, 2016: Babies born to women with Zika late in pregnancy fare better
A study of pregnant women infected with the virus in Colombia found that more than 90% of those infected with the virus during their third trimester gave birth to babies who seem to be healthy, with no effects from the virus. The majority of women in the study infected earlier in their pregnancies had not yet given birth, so the outcomes are still unknown, but the authors of this new study believe their findings suggest that the infection later in pregnancy is not lined to structural abnormalities in a developing fetus. Previous research
indicated that the infection causes problems at any point during pregnancy.
June 2, 2016: Case report questions whether Zika can be transmitted by kissing
Authors of a case report published in the New England Journal of Medicine
say, "Transmission of Zika through saliva is an important question that should be investigated." The report details how how a man who had traveled to Rio infected his female sexual partner, who had not traveled. Her urine and saliva tested positive for the virus, but a vaginal swab did not. The researchers believe she was infected via oral sex but said they cannot rule out the possibility that the virus was transmitted by other body fluids, such as "pre-ejaculate secretions or saliva exchanged through deep kissing."
May 31, 2016: Baby born in N.J. with Zika-related microcephaly
A baby girl was born with "significant microcephaly" at Hackensack University Medical Center. The mother, who does not want to be identified, is from Honduras. Doctors believe she contracted the virus during her second trimester of pregnancy. She traveled to New Jersey, where she has relatives, in search of better medical care, knowing that her baby was at risk for having Zika-related problems.
May 31, 2016: WHO updates guidelines for sex after travel to Zika areas
The WHO updates its recommendations for preventing sexual transmission of the the Zika virus. The revised guidelines say individuals who have traveled to areas where the virus is spreading should abstain or use a condom for eight weeks after returning home. Previously, the recommendation was to wait four weeks. In addition, men who have Zika symptoms should take these measures for six months. The agency later added clarification
that couples should be "informed about the options to consider before conceiving [a child] including delaying pregnancy."
May 26, 2016: Stronger evidence of eye problems among babies born with Zika-related birth defects
Researchers looked at infants born in Brazil between May and December 2015 with microcephaly and found that those with smaller heads and those whose mothers had symptoms of Zika virus during their first trimester of pregnancy were more likely to have eye abnormalities. The findings
build on previous research
into the impact the virus-related birth defect has on vision.
May 25, 2016: Report estimates pregnant women with Zika have up to 13% risk of have an affected baby
A report published in the New England Journal of Medicine
estimates the risk that a pregnant woman infected with the Zika virus during the first trimester of pregnancy has a one to 13% chance that her baby will have microcephaly. The researchers from Harvard and the CDC also found the risk was "negligible" among women infected with the virus later in their pregnancy.
May 23, 2016: Researcher accidentally infects herself with the Zika virus
A researcher at the University of Pittsburgh accidentally infected herself with the Zika virus while conducting an experiment in a lab, the university and local health officials later said. She developed symptoms nine days later. She has since recovered and returned to work.
May 17, 2016: Zika virus is cloned, paving way for vaccine
Scientists clone the Zika virus
, allowing researchers to make and study the virus in test tubes and Petri dishes, hastening the search for a vaccine to prevent the infection. The team of researchers was also able to infect mosquitoes and mice with the cloned version.
However, on Capitol Hill, the House and Senate clash
on how to fund the Zika emergency effort.
May 13, 2016: First US case of microcephaly from locally transmitted Zika
A baby is born in Puerto Rico with microcephaly, the first case in the United States or a territory linked to local transmission of the virus. Previously, a Hawaiian woman had given birth to a child with the condition, but she had gotten the virus while traveling abroad.
April 29, 2016: First US death from Zika complications
A 70-year-old Puerto Rican man is the first person to die
in the United States or its territories from Zika-related complications. The man recovered from the virus but developed a bleeding disorder a few days later that led to his death. It is the ninth known case of bleeding associated with Zika; four of those patients died.
On the same day, the FDA gives an emergency use designation for the first commercial test for Zika
, speeding the process of diagnosing the virus and increasing the numbers of testing sites.
April 7, 2016: Zika definitely causes microcephaly and Guillain-Barré
The WHO says it is a fact that the Zika virus is causing microcephaly in babies and Guillain-Barré Syndrome
. In Washington, President Obama asks for $1.9 billion in emergency funding
from Congress to fight the virus.
April 6, 2016: Zika is transmitted by sex in Texas
While experts wait for the first mosquito bite that causes Zika to occur in the United States, the unexpected happens: the first case of locally acquired Zika via sex
. The revelation startles the scientific world and puts a new perspective on how the virus might spread.
March 30, 2016: Doctors struggle to understand Zika's effect on developing fetus
Studies are released that show Zika's effect on a developing fetus could occur throughout a pregnancy
and affect more than brain size and head circumference. Frieden says, "The more we learn about Zika in pregnancy, the more concerned we are."
March 25, 2016: CDC updates Zika recommendations for sex and pregnancy
Growing concern over how long the virus can linger leads the CDC to update its guidance f
or women who have had Zika: Wait at least two months before getting pregnant. Men should use condoms, the right way, for at least six months after exposure to the virus.
February 26, 2016: CDC to pregnant women: Don't go at all
The CDC hardens its advisory on travel, telling pregnant women or those trying to become pregnant not to travel to any of the countries where Zika is circulating, including Brazil for the August 5-21 Olympic Games and the September 7-18 Paralympic Games.
February 20, 2016: Zika genome is unraveled
Brazilian scientists say they have deciphered the genome for the Zika virus
, a key step toward understanding how it behaves in the human body so a vaccine can be developed.
February 17, 2016: No link between pesticides and Zika
Brazilian health officials and the WHO deny a link between a common pesticide
used in water tanks to kill mosquito larvae and the Zika outbreak, a theory proposed by a group of doctors from Argentina.
February 5, 2016: CDC to men: Use a condom, or don't have sex
To keep unborn babies from the dangers of Zika, men who have been exposed to the virus and have a pregnant partner should use a condom throughout the entire pregnancy or abstain from sex altogether
, warns the CDC.
February 1, 2016: WHO declares Zika 'public health emergency'
After warning that Zika was "spreading explosively
" thoughout the Americas, with as many as 3 million to 4 million infections expected in the next year, the WHO declares Zika a "public health emergency of international concern."
January 20, 2016: CDC urges Zika screening
With Zika circulating in many of the top vacation spots in the Caribbean and Central and South America, the CDC advises all pregnant women who have recently vacationed there to get tested for Zika
January 17, 2016: Hawaiian baby is born with microcephaly
A Hawaiian woman who lived in Brazil in 2015 gives birth in Oahu to a baby with microcephaly
, a condition in which the baby's head and brain are much smaller than normal. The condition often causes severe developmental delays.
January 15, 2016: CDC warns pregnant women to think twice
The CDC advises all pregnant women or those trying to become pregnant to avoid travel to any of the countries
where Zika is active, including Brazil during the Games.
January 12, 2016: CDC identifies Zika in brain tissue of newborns
The CDC confirms the Zika virus
in samples of brain tissue of two Brazilian babies who died within a day of birth, as well as in fetal tissue from two miscarriages. It is the first definite proof of a potential connection between Zika and the rising number of birth defects, stillbirths and miscarriages in mothers infected with the virus.
November 11, 2015: Zika is a public health emergency
Brazil declares a national public health emergency as numbers of infants born with microcephaly continue to rise.
October 30, 2015: Brazil reports unusual number of birth defects
Nine months after the first cases of Zika, women begin to give birth to babies with an unusual birth defect, microcephaly, in which the baby's head and brain do not develop normally.
February 2015: Brazil sees first cases of Zika but doesn't know what it is
From February through April, Brazil sees 7,000 cases of a mild viral reaction, characterized by rash, fever and red eyes. Zika isn't identified in the blood samples until May. By July 2015, doctors begin seeing a few cases of Guillain-Barré.
In addition, 1,505 blood donors who had no symptoms of the virus test positive for Zika, alerting authorities that the virus could be transmitted via transfusion.
December 2013: Zika found in semen
Throughout the year, Zika spreads among more islands in French Polynesia and the South Pacific. In December, an elderly man returns to the hospital after recovering from the illness, complaining of bloody sperm. Doctors find alarming amounts of the virus in his semen, providing the first evidence that the virus can hide and grow in the immune-privileged area of the testes.
2012: Two distinct strains of virus
Researchers find two geographically distinct lineages of the Zika virus, one from Africa and another from Asia, showing that the virus has mutated. The Yap Island outbreak came from the Asian strain.
September 2008: First case of sexually transmitted Zika in US
A Colorado scientist returns home from Senegal with Zika and gives it to his wife via sex
. Although documented, the case is considered inconclusive until the fall of 2015, when a couple in Dallas pass the virus during sex.
April 2007: Zika attacks
The first large outbreak of Zika in people is documented in the Federated States of Micronesia on the island of Yap. Nearly 73% of the island's residents get the virus. Before this, according to the WHO, there had been only 14 cases of Zika in humans anywhere in the world.
1964-83: Zika spreads from Africa to Asia
Tracking the virus via mosquito, researchers find that Zika is spreading across Africa toward Cape Verde while making its way to India, Indonesia, Malaysia and Pakistan.
1964: First active case of Zika virus
While researchers had found antibodies in the blood of people in both Uganda and the United Republic of Tanzania as far back as 1952, this is the first known case of active virus in humans. The infected man developed a pinkish rash over most of his body but reported the illness as "mild," with none of the pain associated with dengue and chikungunya.
1947: Zika emerges from the rainforest
While studying yellow fever in the middle of Uganda's beautiful Zika forest, not far from Lake Victoria, a Scottish medical entomologist named Alexander Haddow stumbles across a new virus
in the blood of a rhesus monkey with a fever. He and colleague George Dick name it Zika, after the forest in which it was identified. By the next year, they find the virus in a local mosquito, establishing the route of transmission.