Zika

West Nile virus (WNV) is a single-stranded RNA virus that belongs to the family Flaviviridae, genus Flavivirus. This family includes several important human arthropod-borne pathogens, such as dengue (DENV), Zika (ZIKV), tick-borne encephalitis (TBEV), yellow fever (YFV) or Japanese encephalitis (JEV) virus. Structurally, it is an enveloped, spherical virus about 40-50 nm in diameter with a lipid bilayer membrane surrounding a capsid core. The genome codes for seven nonstructural proteins and three structural proteins: the envelope, membrane, and capsid proteins. Following a bite from WNV-infected mosquitoes, the virus reaches cells through the blood. It then multiplies in tissues and produces a low-level viremia, which decreases with the appearance of anti-WNV IgM antibodies. It subsequently infects organs (such as spleen, liver, kidney and CNS) and has also been detected in the urine of a patient 8 days after the onset of symptoms.

Zika virus is mainly transmitted through the bite of an infected mosquito of the genus Aedes, especially Aedes aegypti, which is responsible for the transmission of other diseases such as yellow fever, Chikungunya, dengue, and West Nile Virus. It is a mosquito prevalent mainly in tropical and subtropical areas of Africa, South America, the Middle East, Southeast Asia, the Pacific, the Indian Islands, and northern Australia.

The mosquito's distribution is due to climatic conditions, which prevent it from living in temperate or cold regions (this could mean a greater spread even in our latitudes as global temperatures rise). There is also a vector capable of moving into such regions, the Aedes albopictus mosquito (the common tiger mosquito), but it is less competent at transmitting aegypti. Zika virus can also be transmitted by sexual contact, blood transfusions, and organ transplantation. A pregnant woman can transmit Zika virus to her fetus during pregnancy or delivery. The virus has also been found in breast milk, but transmission through breastfeeding has not yet been confirmed.

The first major outbreak of Zika disease that moved global public health interest was reported in 2007 in Yap Island, Micronesia.
From 2007 to 2018, Zika virus transmission has been documented in 86 countries in Africa, the Americas, Asia, and the Pacific. Of great alarm to the scientific community has been the steady progression of the infection's geographic distribution in the Americas, starting in 2015, affecting as many as 33 U.S. countries, eventually infecting more than 1.5 million people in Brazil. Zika-associated microcephaly and other fetal malformations has been a public health emergency of international concern after being reported in more than 1,000 cases in Brazil.

The incubation period of Zika is usually between 3 and 14 days.
The infection is in most cases (around 80 percent) asymptomatic. When present, symptoms are nonspecific and manifest as flu-like, with fever, joint pain, and conjunctivitis. A more characteristic symptom is the appearance of a maculopapular rash.
The possibility of the disease developing severe symptoms is rare, as is the associated mortality. However, cases of the onset of Guillain-Barré syndrome have been observed in patients with suspected or confirmed infection.
The most severe effects occur during pregnancy, when the infection can cause severe damage to the fetus, such as brain defects, microcephaly, limb contractures, eye abnormalities, and hearing loss. The risk of congenital malformations following infection during pregnancy remains unknown; about 5-15% of babies born to Zika virus-infected women during pregnancy have evidence of Zika-related complications.

Preliminary diagnosis for Zika is based on clinical signs and especially history of any travel to areas endemic for the virus. Laboratory diagnosis is serologic, by detection of the virus, nucleic acid or
specific immunoglobulin and antibodies.

To date, no specific antiviral treatment is available for Zika virus disease. Treatment consists of symptom support and may include hydration, analgesics, and antipyretics, taking care to avoid aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), which should be avoided until it is certain that it is not dengue, to reduce the risk of bleeding.

Prevention for dengue transmission begins with proper behavioral prophylaxis, especially during the day, a time when mosquitoes are most active.

• Use an effective mosquito repellent: the Centers for Disease Control and Prevention (CDC) recommends repellents with the following active ingredients: DEET (>25%); Picaridin; IR3535; Eucalyptus Lemon Oil (OLE); Para-menthane-diol; 2- undecanone.
• Cover up: use clothes that cover legs and arms, preferably light colored.
• Check the environment around you: standing water is a perfect habitat for mosquitoes to breed. Make sure there is no stagnant water in: discarded tires or industrial containers, swimming pools, storm drains and saucers. To reduce the risk ti transmission, systematic control through pest control campaigns against the Aedes population turns out to be a key intervention

Regarding prevention for sexual transmission, WHO has compiled behavioral guidelines:

• Travelers who have traveled to an area endemic for Zika should adopt mechanical protection during sexual intercourse, at least for 3 months men and 2 months women, even in the absence of symptoms;
• Pregnant women, before embarking on a trip to an endemic area, should consult their physician to assess the risk and consider postponing the trip
• Pregnant women traveling to an area endemic for Zika should practice sexual abstinence or have protected sex for the duration of the pregnancy
• The partner of a pregnant woman traveling to an area with a Zika outbreak should use mechanical means of protection during sexual intercourse for the duration of the pregnancy.