Zika Virus Infection Fast Facts | CNN



CNN
 — 

Here’s a look at Zika virus, an illness spread through mosquito bites that can cause birth defects and other neurological defects.

Sources: Centers for Disease Control and Prevention (CDC), World Health Organization (WHO) and CNN

Zika virus is a flavivirus, part of the same family as yellow fever, West Nile, chikungunya and dengue fever.

Zika is primarily transmitted through the bite of an infected female Aedes aegypti mosquito. It becomes infected from biting an infected human and then transmits the virus to another person. The Aedes aegypti mosquito is an aggressive species, active day and night and usually bites when it is light out. The virus can be transmitted from a pregnant woman to her fetus, through sexual contact, blood transfusion or by needle.

The FDA approved the first human trial of a Zika vaccine in June 2016. As of May 2022, there is still no available vaccine or medication.

Cases including confirmed, probable or suspected cases of Zika in US states and territories updated by the CDC.

Most people infected with Zika virus won’t have symptoms. If there are symptoms, they will last for a few days to a week.

Fever, rash, joint pain and conjunctivitis (red eyes) are the most common symptoms. Some patients may also experience muscle pain or headaches.

Zika virus infection during pregnancy can cause microcephaly, a neurological disorder that results in babies being born with abnormally small heads. Microcephaly can cause severe developmental issues and sometimes death. A Zika infection may cause other birth defects, including eye problems, hearing loss and impaired growth. Miscarriage can also occur.

An August 2018 report published by the CDC estimates that nearly one in seven babies born to women infected with the Zika virus while pregnant had one or more health problems possibly caused by the virus, including microcephaly.

According to the CDC, there is no evidence that previous infection will affect future pregnancies.

(Sources: WHO, CDC and CNN)

1947 – The Zika virus is first discovered in a monkey by scientists studying yellow fever in Uganda’s Zika forest.

1948 – The virus is isolated from Aedes africanus mosquito samples in the Zika forest.

1964 – First active case of Zika virus found in humans. While researchers had found antibodies in the blood of people in both Uganda and in Tanzania as far back as 1952, this is the first known case of the 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.

1960s-1980s – A small number of countries in West Africa and Asia find Zika in mosquitoes, and isolated, rare cases are reported in humans.

April-July 2007 – The first major outbreak in humans occurs on Yap Island, Federated States of Micronesia. Of the suspected 185 cases reported, 49 are confirmed, and 59 are considered probable. There are an additional 77 suspected cases. No deaths are reported.

2008 – Two American researchers studying in Senegal become ill with the Zika virus after returning to the United States. Subsequently, one of the researchers transmits the virus to his wife.

2013-2014 – A large outbreak of Zika occurs in French Polynesia, with about 32,000 suspected cases. There are also outbreaks in the Pacific Islands during this time. An uptick in cases of Guillain-Barré Syndrome during the same period suggests a possible link between the Zika virus and the rare neurological syndrome. However, it was not proven because the islands were also experiencing an outbreak of dengue fever at the time.

March 2015 – Brazil alerts the WHO to an illness with skin rash that is present in the northeastern region of the country. From February 2015 to April 29, 2015, nearly 7,000 cases of illness with a skin rash are reported. Later in the month, Brazil provides additional information to WHO on the illnesses.

April 29, 2015 – A state laboratory in Brazil informs the WHO that preliminary samples have tested positive for the Zika virus.

May 7, 2015 – The outbreak of the Zika virus in Brazil prompts the WHO and the Pan American Health Organization (PAHO) to issue an epidemiological alert.

October 30, 2015 – Brazil reports an increase in the cases of microcephaly, babies born with abnormally small heads: 54 cases between August and October 30.

November 11, 2015 – Brazil declares a national public health emergency as the number of newborns with microcephaly continues to rise.

November 27, 2015 – Brazil reports it is examining 739 cases of microcephaly.

November 28, 2015 – Brazil reports three deaths from Zika infection: two adults and one newborn.

January 15 and 22, 2016 – The CDC advises all pregnant women or those trying to become pregnant to postpone travel or consult their physicians prior to traveling to any of the countries where Zika is active.

February 2016 – The CDC reports Zika virus in brain tissue samples from two Brazilian babies who died within a day of birth, as well as in fetal tissue from two miscarriages providing the first proof of a potential connection between Zika and the rising number of birth defects, stillbirths and miscarriages in mothers infected with the virus.

February 1, 2016 – The WHO declares Zika a Public Health Emergency of International Concern due to the increase of neurological disorders, such as microcephaly, in areas of French Polynesia and Brazil.

February 8, 2016 – The CDC elevates its Emergency Operations Center for Zika to Level 1, the highest level of response at the CDC.

February 26, 2016 – Amid indications that the mosquito-borne Zika virus is causing microcephaly in newborns, the CDC advises pregnant women to “consider not going” to the Olympics in Rio de Janeiro. The CDC later strengthens the advisory, telling pregnant women, “Do not go to the Olympics.”

March 4, 2016 – The US Olympic Committee announces the formation of an infectious disease advisory group to help the USOC establish “best practices regarding the mitigation, assessment and management of infectious disease, paying particular attention to how issues may affect athletes and staff participating in the upcoming Olympic and Paralympic Games.”

April 13, 2016 – During a press briefing, CDC Director Thomas Frieden said, “It is now clear the CDC has concluded that Zika does cause microcephaly. This confirmation is based on a thorough review of the best scientific evidence conducted by CDC and other experts in maternal and fetal health and mosquito-borne diseases.”

May 27, 2016 – More than 100 prominent doctors and scientists sign an open letter to WHO Director General Margaret Chan, calling for the summer Olympic Games in Rio de Janeiro to be postponed or moved “in the name of public health” due to the widening Zika outbreak in Brazil.

July 8, 2016 – Health officials in Utah report the first Zika-related death in the continental United States.

August 1, 2016 – Pregnant women and their partners are advised by the CDC not to visit the Miami neighborhood of Wynwood as four cases of the disease have been reported in the small community and local mosquitoes are believed to be spreading the infection.

September 19, 2016 – The CDC announces that it has successfully reduced the population of Zika-carrying mosquitoes in Wynwood and lifts its advisory against travel to the community.

November 18, 2016 – The WHO declares that the Zika virus outbreak is no longer a public health emergency, shifting the focus to long-term plans to research the disease and birth defects linked to the virus.

November 28, 2016 – Health officials announce Texas has become the second state in the continental United States to confirm a locally transmitted case of Zika virus.

September 29, 2017 – The CDC deactivates its emergency response for Zika virus, which was activated in January 2016.

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Understanding how mosquitoes smell humans could save thousands of human lives | CNN



CNN
 — 

Of the more than 3,000 species of mosquitoes in the world, just a small number have evolved to specialize in sucking human blood.

How human-biting mosquitoes track us down so effectively isn’t currently known, but it matters, since they don’t just make us itch. They also carry dangerous diseases such as Zika, dengue, West Nile virus and malaria that can be deadly.

In fact, stopping these pesky insects in their tracks could save up to half a million lives lost to those diseases each year.

“In each of those cases where a mosquito has evolved to bite humans — which has only happened two or three times — they become nasty disease vectors,” said Carolyn “Lindy” McBride, an assistant professor of ecology and evolutionary biology at the Princeton Neuroscience Institute in New Jersey.

That’s why she wants to understand how they find and target humans.

“Mosquitoes mostly choose what to bite based on odor,” said McBride, whose lab focuses on the Aedes aegypti mosquito species that evolved to bite humans specifically.

Only female mosquitoes suck blood since they need it to produce their eggs. Knowing how a potentially disease-carrying female mosquito sniffs out a person, while ignoring other warm-blooded animals, is a key query.

Once that’s better known, much more effective repellents — or bait to lure mosquitoes away from humans — could be made, saving lives, said Christopher Potter, associate professor of neuroscience at Johns Hopkins University’s Center for Sensory Biology.

If scientists can control their sense of smell, “we can really control what these mosquitoes are doing,” said Potter, who studies another human-specific mosquito, Anopheles, which carries malaria.

It’s not an easy question to answer, since any animal smell is made up of hundreds of chemical compounds mixed together in specific ratios.

“The actual chemicals that are found in human odor are basically the same as the chemicals found in animal odor — it’s the ratios and the relative abundance of those compounds in human mixtures that’s unique,” said McBride, whose research focuses on those issues.

Each time a hungry female mosquito flies by, it’s doing complex chemical math in its tiny brain, figuring out what’s a human, what’s dog and what’s a flower.

“To investigate, we decided to record neural activity in the brain of females while exposing them to natural human and animal odor extracts,” wrote Zhilei Zhao, a graduate student in McBride’s lab, in a Twitter thread describing the lab’s work. It took four years to develop “the necessary genetic reagents, odor delivery systems, and analytical approaches,” Zhao wrote.

(From left) Noah Rose, a postdoctoral researcher at Princeton, and Gilbert Bianquinche survey a tree hole near Kedougou, Senegal, for Aedes aegypti larvae. More than half of the world's population lives in areas where Aedes aegypti mosquitoes are present.

McBride’s lab team created a library of the chemical composition of animal odors. “That data set doesn’t really exist — so we decided to go out and collect it ourselves,” said Jessica Zung, a graduate student in McBride’s lab.

Zung has collected scent samples from about 40 different animals so far, including guinea pigs, rats, quail and more.

Comparing some of those to the 16 human samples, something jumped out. Decanal, a simple, common compound, is particularly abundant in human skin, Zung said.

Ubiquitous in the natural world, in humans, decanal comes from another, more complex compound. Zung dug into the archives to find research from the 1970s (much of it originally done to find an acne cure) that detailed how when one component of our skin’s natural oils, sapienic acid, breaks down, decanal is left over. This acid (as indicated by its name) is only found in human beings. It’s what likely leads to the high levels of decanal that help the mosquitoes smell their way to us, but more studies need to be done.

Understanding what the mosquitoes are sniffing out is only part of the story; knowing how they do it is also important. To see exactly how mosquitoes use this sense, scientists bred genetically modified Aedes aegypti mosquitoes “so that we could cut open their little tiny heads and put them under a fancy microscope and actually watch neurons firing when they’re exposed to human and animal odors,” McBride said.

The research team already knew that mosquitoes have about 60 different types of neurons that sense odors, so when they looked in the insects’ brains, they thought they might see a lot of activity. But it was surprisingly quiet, meaning that the signal was perhaps quite simple, down to just a couple types of neurons.

“One type of neuron responded really strongly to both humans and animals. Another type of neuron responded to both — but it responded much more strongly to humans than animals,” McBride said of that work. So it may be as simple as that mosquito’s brain comparing just two types of neurons.

This kind of research has only been possible since the technology to study mosquito brains in detail became available, which only happened recently. “It’s been traditionally very hard to study this at the level we’re doing it now,” Potter said.

Incredibly, mosquitoes that target humans have evolved to be able to do this in just the last 5,000 years, so it’s a “really amazing example of rapid evolution,” McBride said.

The Aedes aegypti, aka “yellow fever mosquito” also carries dengue, Zika and chikungunya. The critter originated in Africa and likely made its way to its current range in the southern United States and Central and South America on slave ships during the 1600s, according to McBride.

These diseases combined kill and sicken thousands of people a year, which is why mosquitoes have been called “the world’s deadliest animal” by the US Centers for Disease Control and Prevention. McBride and Potter both hope their work could be used by others working on repellents and attractants to prevent disease.

As far as insider knowledge on how to keep from being bitten in your own backyard, McBride said she uses a fan.

“Have it blow air over where you’re sitting outside or over the barbecue or under the table where they’re biting your feet.” It’s not that you’re blowing the scent around to knock the mosquitoes off track, she said.

It’s simply because these deadly creatures, McBride said, “are not great fliers.”



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