Zika Virus Host Targets and Pathogenic Mechanisms

Zika virus belongs to the Flaviviridae family, Flavivirus genus, a single stranded positive stranded RNA virus with a diameter of 20nm. It is an arbovirus transmitted through mosquitoes, and its host is unclear. It is mainly found in wild primates and tree dwelling mosquitoes.

Etiology

Zika virus belongs to the Flaviviridae family, Flavivirus genus, a single stranded positive stranded RNA virus with a diameter of 20nm. It is an arbovirus transmitted through mosquitoes, and its host is unclear. It mainly circulates in wild primates and tree dwelling mosquitoes, such as Aedes mosquitoes in Africa. The virus was first discovered by chance in 1947 through a yellow fever surveillance network in rhesus monkeys in the Zika jungle of Uganda, and later in 1952 in populations in Uganda and Tanzania. The virus activity has always been relatively hidden, with sporadic cases of Zika virus infection only in Africa, the Americas, Asia, and the Pacific around the equator. The earliest outbreak of the epidemic occurred in 2007 on Yap Island in the Western Pacific's Micronesia Islands, and a larger outbreak occurred in 2013-2014 in French Polynesia, Oceania, infecting approximately 32000 people. Aedes mosquitoes also transmit three other viruses in the family Flaviviridae, including dengue virus, chikungunya virus, and yellow fever virus, which are mainly prevalent in tropical and subtropical regions.

Figure 1. The evolution of Zika virus from Asia to the Americas.( Liu, Zhong-Yu,et al.2019)

Clinical Manifestations

• The incubation period of Zika virus disease (the time from exposure to symptoms) is not yet clear and may be several days. Only about 20% of Zika virus infected individuals will exhibit mild symptoms, typical of which include acute onset low-grade fever, papules, joint pain (mainly affecting the small joints of the hands and feet), conjunctivitis, and other symptoms such as muscle pain, headache, orbital pain, and weakness. Other rare symptoms include abdominal pain, nausea, vomiting, mucosal ulcers, and skin itching. The symptoms are usually mild and last less than a week, and serious conditions that require hospitalization are not common. During the outbreaks in French Polynesia and Brazil in 2013 and 2015, there were reports that Zika virus disease may cause neurological and autoimmune complications.

Diagnosis

The diagnosis of Zika virus infection is based on symptoms and epidemiological history (such as mosquito bites or traveling to areas known to have Zika virus). Due to the cross reactivity of Zika virus with other yellow viruses such as dengue fever, West Nile virus, and yellow fever, it may be difficult to make a diagnosis through serological methods. Reverse transcription polymerase chain reaction (RT-PCR) and virus isolation and culture in blood can confirm the diagnosis. If Zika virus RNA is detected as positive in peripheral serum within 7 days of onset, it can be diagnosed. However, due to the short positive window of RT-PCR (3-7 days), which means the viremia period is short, negative results outside the positive window cannot rule out infection.

Anti-Zika Virus Antibodies

Zika Antigens