Zika Virus. Zika Virus. Priyanka Halde. 3 rd Year, MGM Institute of Health Sciences, Navi Mumbai December, 2016

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1 Priyanka Halde 3 rd Year, MGM Institute of Health Sciences, Navi Mumbai December, 2016

2 Introduction Zika virus is an emerging mosquito-borne virus that was first identified in Zika Forest in Uganda in 1947 in rhesus monkeys through a monitoring network of sylvatic yellow fever. It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania. Outbreaks of Zika virus disease have been recorded in Africa, the Americas, Asia and the Pacific. Genre: Flavivirus Vector: Aedes mosquitoes (which usually bite during the day with peaks during early and late afternoon/evening hours) Reservoir: Unknown About the virus Zika virions are typically icosahedral-shaped. They are enveloped, nanometer in diameter. The genome is a positive strand RNA enclosed in a capsid and surrounded by a membrane. The RNA contains 10,794 nucleotides encoding 3,419 amino acids. The virus is inactivated by ether, sodium dexoxycholate and chloroform.

3 Pathophysiology Zika virus is well-adapted to grow in various hosts, ranging from arthropods to vertebrates. Viral attachment to unidentified cellular receptors is mediated by the E (envelope) glycoprotein. This is followed by endocytic uptake and then uncoating of the nucleocapsid and release of viral RNA into the cytoplasm. A viral polyprotein is produced and modified by the endoplasmic reticulum. Immature virions collect both in the endoplasmic reticulum and in secretory vesicles before being released. The virus resembles other known flavivirus structures with the exception of approximately 10 amino acids surrounding the Asn154 glycosylation site in each of the 180 envelope glycoproteins comprising the icosahedral shell, the carbohydrate moiety of which may be the attachment site of the virus to host cells. Transmission Zika virus is transmitted to people through the bite of an infected mosquito from the Aedes genus, mainly Aedes aegypti in tropical regions. This is the same mosquito that transmits dengue, chikungunya and yellow fever. However, sexual transmission of Zika virus has is also possible through

4 blood transfusion, vertical transmission from pregnant mothers to their foetus. Symptoms

5 Incubation period 3 to 12 days Most people infected with Zika virus won t even know they have the disease because they won t have symptoms. The most common symptoms of Zika are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache. The incubation period (the time from exposure to symptoms) for Zika virus disease is not known, but is likely to be a few days to a week. o If a pregnant women develops a fever, rash, joint pain, or red eyes within 2 weeks after traveling to a place where Zika has been reported she must immediately see a doctor. She must surely tell the doctor or other healthcare provider where she travelled. People usually don t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected. Zika virus usually remains in the blood of an infected person for about a week but it can be found longer in some people. Once a person has been infected, he or she is likely to be protected from future infections.

6 Zika virus and Pregnancy Zika virus can pass from a pregnant woman to her fetus during pregnancy or around the time of birth. Zika infection in pregnancy is a cause of microcephaly and other severe fetal brain defects. o Microcephaly: birth defect in which a baby s head is smaller than expected when compared to babies of the same sex and age. o Previous infection will not affect future pregnancies. Other problems have been detected in pregnancies among fetuses and infants infected with Zika virus before birth. Scientists are studying the full range of other potential health problems that Zika virus infection during pregnancy may cause. No reports of infants getting Zika through breastfeeding. Microcephaly Microcephaly is a complication of Zika virus when the virus is transmitted from mother to the foetus. Microcephaly is a condition where a baby s head is much smaller than expected. During pregnancy, a baby s head grows because the baby s brain grows. Microcephaly can occur because a baby s brain has not developed

7 properly during pregnancy or has stopped growing after birth, which results in a smaller head size. Babies with microcephaly can have a range of other problems, depending on how severe their microcephaly is. Microcephaly has been linked with the following problems: Seizures Developmental delay, such as problems with speech or other developmental milestones (like sitting, standing, and walking) Intellectual disability (decreased ability to learn and function in daily life) Problems with movement and balance Feeding problems, such as difficulty swallowing Hearing loss Vision problems These problems can range from mild to severe and are often lifelong. Because the baby s brain is small and underdeveloped, babies with severe microcephaly can have more of these problems, or have more difficulty with them, than babies with milder microcephaly. Severe microcephaly also can be life-threatening. Because it is difficult to predict at birth what problems a baby will have from microcephaly.

8 Guillain-Barré Syndrome (GBS)

9 GBS is very likely triggered by Zika in a small proportion of infections, much as it is after a variety of other infections. GBS is an uncommon sickness of the nervous system in which a person s own immune system damages the nerve cells, causing muscle weakness, and sometimes, paralysis. Lab Diagnosis There is no widely available test for Zika infection. In most people, diagnosis is based on clinical symptoms and epidemiological circumstances (such as Zika outbreak in the patient s area or trips to areas where the virus is circulating). Diagnostic tests for ZIKV infection include: 1. Polymersase Chain Reaction: Nucleic acid detection by reverse transcriptase-polymerase chain reaction (RT-PCR) targeting the non-structural protein 5 genomic region is the primary means of diagnosis. It is useful in the first 3-5 days after the onset of symptoms. 2. Serological Tests: An ELISA has been developed to detect IgM to ZIKV only after five days. Because it is closely related to dengue and yellow fever, it may crossreact with antibody tests for those viruses. 3. Nucleic Acid Amplification Test: Nucleic acid amplification test (NAT) for detection of viral RNA can also be performed. 4. Plaque Reduction Neutralization Assay: The Plaque reduction neutralization assay generally has improved specificity over immunoassays, but may still yield cross-reactive results in secondary flavivirus infections. Infection with Zika virus may be suspected based on symptoms and recent history of travel (e.g. residence or travel to an area where Zika virus is known to be present). Also, Zika virus diagnosis can only be confirmed by laboratory testing for the presence of Zika virus RNA in the blood or other body fluids, such as urine or saliva.

10 Treatment There is no specific medicine or vaccine for Zika virus Treat symptoms o Resting o Drinking fluids to prevent dehydration o acetaminophen (Tylenol ) to reduce fever and pain Protection from mosquito bites. During the first week of illness, Zika virus can be found in blood for about a week. If a mosquito bites the person, it becomes infected and can pass the infection to others. Prevention 1. Prevention against mosquitoes - Zika is primarily transmitted through mosquito bites. Keep mosquitoes out of your home or hotel o Stay in places with air conditioning and with window/door screens. o Do not leave doors propped open. Keep mosquitoes out of your home or hotel. o Once a week, empty and scrub, turn over, cover, or throw out items that hold water. Mosquitos lay eggs near water. o Tightly cover water storage containers (buckets, cisterns, rain barrels) so that mosquitos cannot get inside to lay eggs.

11 o If you have a septic tank, repair cracks or gaps. o When traveling, use a bed net if air conditioned or screened rooms are not available or if sleeping outdoors. o Wear long-sleeved shirts and long pants. o Use permethrin to treat clothing and gear or buy permethrintreated clothing and gear. Read product information to find out how long the protection will last. Use Environmental Protection Agency (EPA)-registered insect repellents o Use a repellent with DEET, picaridin, IR535, or oil of lemon eucalyptus, or para-menthane-diol For babies and children o Do not use insect repellents on babies younger than 2 months old. o Do not use products containing oil of lemon eucalyptus or paramenthane-diol on children younger than 3 years old. o Cover crib, stroller, and baby carrier with mosquito netting.

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13 2. Protect your partner Zika virus can be spread by a man infected with Zika to his partners. In known cases of sexual transmission, the men had Zika symptoms. From these cases, we know the virus can be spread when the man has symptoms, before symptoms start, and after symptoms end. The virus can stay in semen longer than in blood. Men with a pregnant partner who live in or traveled to an area with Zika: o Use a condom every time you have sex or do not have sex during the pregnancy. o This includes vaginal, anal, or oral sex.

14 3. Homework before travelling If you are pregnant, do not travel to areas with Zika. If you must travel, talk to your doctor or other healthcare provider before your trip. If you are trying to get pregnant, talk to your doctor or other healthcare provider before you travel. If you choose to travel: o Strictly follow steps to prevent mosquito bites to protect yourself and your family. o Even if you do not feel sick, travelers returning t from an area with Zika should take steps to prevent mosquito bites for 3 weeks so they do not spread Zika to uninfected mosquitos.

15 References 1) 2) 3) 4) 5) 6) 7) 8) 9)

16 About the Author Priyanka Halde 3 rd Year MBBS Student, MGM Institute of Health Sciences, Navi Mumbai PlexusMD Management intern Priyanka wishes to specialize in Paediatrics Connect at: haldepriyanka@gmail.com Capsule Reviewed by PlexusMD Editorial Panel

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