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Prevention and Transmission Zika Virus

prevention-and-transmission-zika-virus

Zika virus

First, about how Zika is transmitted. Zika is transmitted by the Aedes mosquitoes, primarily Aedes aegypti and also Aedes albopictus. These mosquitoes are found in tropical and subtropical areas, and breed in small puddles of water around the home. They breed in trash, tires, flowerpots, containers, anything that holds small amounts of water. It's important to remember that these mosquitoes bite during the day. And these are the same mosquitoes that also transmit dengue, yellow fever, chikungunya, and other viruses.


So, there are three major ways that Zika can be transmitted. The primary mode is by the bite of an infected mosquito. Second, and importantly is Zika can be transmitted from mother to child during pregnancy and delivery. And finally, Zika can also be transmitted person-to-person through sexual contact, through a blood transfusion, or organ transplantation.


So, next, we'll talk about the signs and symptoms of Zika infection. The majority of people with Zika virus infection actually have no symptoms. Probably 80% of people have no symptoms. And when symptoms occur, they're usually very mild: mild fever, rash, conjunctivitis, muscle, and joint pain, headache, and general malaise. Symptoms are brief and self-limited, usually lasting about two to seven days.


I'm going to talk a little bit about the history of Zika infection and what happened most recently. But historically, the very first evidence of human infection was in Uganda and Tanzania in 1952. Subsequent to that, they were just rare, sporadic cases reported across Africa, Asia, and the Pacific. Cases were mild, rare, not really known to cause any adverse pregnancy outcomes. The first major outbreak happened around 2007 to 2014, where Zika disease outbreaks emerged in the Pacific Islands.

And then in 2015, something very different happened. There was a major outbreak of Zika disease that emerged in Brazil and then Colombia. In March 2015, there was an outbreak of cases with reports of rash and fever. But then, in October of 2015, infants were born with microcephaly and other severe neurologic complications. And this was new. Also what occurred, was the emergence of Guillain-Barré syndrome, a severe neurologic disease that was happening primarily in adults. From 2015, and then through 2017, there was the rapid spread of Zika and microcephaly and its other complications that spread rapidly throughout the Americas, the Caribbean, and beyond.

In 2016, the Zika virus and its associated complications were declared a Public Health Emergency of International Concern, or a "PHEIC". All told, over 80 countries and territories reported Zika virus transmission. There was a large, global coordinator response for detection, control, and emerging research. By 2017, the end of the PHEIC was declared, but the end of - the problem of Zika has continued. Our goal now is to transition the Zika program to a long-term strategy, integrated with public health programs, and maternal-child health, and vector-borne diseases. There's a persistent need to continue to track infection and disease, focusing on prevention and control, and research.


This slide summarizes complications of Zika virus infection in pregnancy. In Asia, the Americas, and the Pacific, infection in pregnancy results in microcephaly, or a small head circumference below the third percentile for the infant's birth weight and gestational age. Other anomalies have also been identified. Secondly, other adverse pregnancy outcomes have been reported: miscarriage, stillbirth, infant brain calcifications, and other neurologic problems affecting infants. Finally, Zika can cause other problems, such as Guillain-Barré syndrome in adults, seizures, and other severe neurologic complications.


What we're left with now is a summary of the global spread of the Zika virus and disease. The reasons for this outbreak and the rapid spread of infection and severe disease in the Americas remain unknown. What we do know is there were two strains of Zika: the African strain and the Asian strain. The outbreak was caused by the Asian strain and new mutations in that virus were identified. To date, based on all known information, microcephaly is only associated with the Asian strain. Birth outcomes from the African strain are unknown. From animal models, it appears that the African strain may increase early fetal loss and severe pregnancy complications. To date in Africa, Zika associated microcephaly has only been found in Cabo Verde and possibly Angola, likely due to the introduction of the Asian strain. Future disease monitoring and research are needed so we can understand Zika transmission and its clinical consequences.


So, even though the emergency and declaration of the emergency is over, we need continued efforts to track Zika transmission and understand what the risk is to pregnant women outside the Americas. Pregnant women should be advised to seek medical care if they develop fever, rash, arthritis, or other symptoms of Zika infection. Pregnant women with symptoms should be tested for the Zika virus and other related infections. All of this should be part of a comprehensive care strategy for pregnant women. The overall goal is to have an integrated program that advances the health of pregnant women and their newborns. Reporting cases of Zika infection and microcephaly through public health systems will strengthen our efforts to monitor transmission and disease outcomes in pregnant women and infants, and help us know what we should be telling women who might be infected.


The risk of microcephaly in Africa remains unknown. In the Americas, the rate of microcephaly is about three to ten percent if the woman is affected in her first trimester with the Asian strain. A fetal ultrasound might be useful for the early detection of microcephaly during pregnancy and helps in monitoring the pregnancy. Infants, as always, should be examined at the time of delivery and head circumference should always be measured as part of a newborn exam. Cases of microcephaly and other birth defects should be reported to public health authorities so we would know if there's an outbreak or an increased incidence of this outcome.


Guillain–Barré syndrome can also be caused by the Zika virus. It's a rare condition that affects a person's immune system and attacks the peripheral nerves. Guillain-Barré syndrome is more common among adult males and is potentially life-threatening.


Prevention of Zika virus means preventing bites of infected mosquitoes. The most important method is to eliminate Aedes mosquito breeding sites. This is the same control measure for dengue, yellow fever, and chikungunya. And that's to eliminate small water receptacles and trash around the home. Also, use of approved household sprays and larvicides could be used as part of a global effort. To prevent the bites of Aedes mosquitoes, one would prevent mosquito bites during the day and early evening through personal protection measures: wearing light-colored clothing and use of insect repellent. Physical barriers on the home, including window screens, closed doors, windows, and bed nets also prevent the bite of an infected mosquito.


Zika virus can also be transmitted by sexual transmission. Men and women returning from areas where transmission of the Zika virus is known to occur are advised to practice safe sex or abstinence for at least six months. In regions with active Zika transmission, pregnant women and their partners are advised to practice safe sex or abstain for the duration of the pregnancy.


Zika virus infection is diagnosed by molecular testing, or RT-PCR, or by an IgM test soon after symptoms. Accurate and simple tests are not yet available. Testing is often not widely available and sometimes done at national or reference laboratories. Affected newborns will likely not have a positive test. The tests detect recent infection, and by the time the infant is delivered, the test is usually not still positive. There's no specific treatment for Zika virus infection. Patients are recommended to rest, drink fluids and manage fever and pain with common medicines. No known treatments are available to prevent birth defects.

As healthcare workers, it's important for you to be confident and a credible source of information about the Zika virus. There's still much that we don't know. You need to explain that the information you're sharing is the most accurate available. We're still learning about this virus. Advice and recommendations will change as more scientific information is discovered.

If the infection in pregnancy is confirmed, women should be provided information about potential risks to the infant and available services. In the tools section, there are examples of questions to which only partial answers are known. Think about how you could answer these questions clearly, knowing the limitations of our knowledge.


If infections in pregnancy is confirmed, women should be provided information about potential risks to the infant and available services. In the tool section, you'll find examples of questions to which only partial answers are known. Think about how you could answer these questions clearly, knowing the limitations of our knowledge. Thank you for your attention and you can find additional tools in the tools section associated with the download of this presentation. Thank you.


Comments

Iqra from East County on May 02, 2021:

Zika is a mosquito-borne disease that has no vaccine nor cure. The best form of prevention is avoiding or repelling mosquitoes. CDC recommendations include: Use insect repellents containing DEET, picaridin, OLE.

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