The human body has a close relationship with the microorganisms such that it harbors more microbes than we can imagine. This also means that the world around us is also home for these tiny creatures. The scientific study of these microorganisms, known as microbiology, covers every aspect, including the study of viruses. Viruses are the smallest agents that can cause infections. They are not capable of surviving outside a living cell. Of all the numerous viruses that are rich in diversity, we will look extensively at the Zika virus- the virus that is stirring up concerns in various parts of the world.
What is Zika virus?
Zika virus (ZIKV) is a microorganism that causes Zika fever. It belongs to a family of viruses called the Flaviviridae. Zika virus is a single-stranded RNA virus, icosahedral in shape, and enveloped by dense projections of membrane and glycoprotein. The incubation period is between 3-12 days with self-limiting symptoms, which makes the infection often go unnoticed.
History of Zika virus
Zika virus is reported to have been isolated from a monkey in the Zika forest of Uganda for the first time in 1947. However, the first established evidence of a transmission from animal to human was in 1952. Subsequent genetic research showed that the virus has always been among us but is spread from one person to another by a mosquito strain common to the tropics and subtropics.
The virus is relatively new in our environment. Not so much was known about it until the major breakout in the year 2015. The outbreak stirred up panic across the globe as the infection spread from South and Central America even to the southern part of the United States in the following year. The outbreak of infections was first reported in northeast Brazil. In the space of two years, the rate of births with microcephaly related to the virus alarmingly spiked.
In the year 2019, there is no report of any confirmed Zika virus disease case from United States territories. On the other hand, there is no reported local transmission of Zika virus in the continental United States, even in Florida and Texas, where local transmission of Zika virus by Aedes species was recorded in 2016 and 2017. In Alaska and Hawaii, there has never been any report of Zika virus transmission by mosquitoes.
Symptoms of Zika virus infection
Many people have mild, self-limiting symptoms, or no symptoms from the Zika virus infection.
In cases where there are symptoms, they are usually mild and run their course for about one week.
The symptoms commonly reported include rash, body itching, high fever, headache, pain in the joints (majorly in the small joints of the hands and feet and associated swelling), muscle pain, conjunctivitis (red eye or pink), lower back pain, pain behind the eyes.
Symptoms of Zika virus infection usually last from a few days to a week. And often, many of the infected persons do not require a hospital stay and rarely die from the infection. Once a person is infected and treated, they may be immune from future Zika infection.
These symptoms are different if the virus is transmitted during pregnancy. If this happens, the developing baby may be severely affected. Zika infection s may lead to miscarriages, stillbirths, or in severe cases, congenital abnormality like microcephaly.
How is Zika virus transmitted
Zika virus is similar to other viruses causing Dengue fever and Yellow fever because the same species of mosquito transmit them all.
It is usually transmitted via mosquito bites but can also be transferred from mother to Child in pregnancy.
Bites from mosquito species Aedes aegypti and Aedes albopictus are notorious for the transmission of the virus.
Sexual transmission has also been reported. It has been said that infected people can spread the virus to their partners via penovaginal, oral, or anal sex.
Treatment of Zika virus infection
The treatment for the Zika virus infection is non-specific. Management is basically for the symptoms manifested in the individual. Treat the fever, headache, and muscle pain with the appropriate medications that are available over the counter.
Why is Zika infection risky for some people?
Even though most cases of Zika virus infections are self-limiting and mild, showing a good prognosis. However, severe congenital disabilities may arise from Zika virus infection during pregnancy. Microcephaly and other severe brain defects have been attributed to Zika infection in pregnancy. Other complications from Zika infection in pregnancy include Gullian-Barré syndrome, congenital malformations, and ophthalmologic abnormalities due to transplacental transmission that has been associated with the Zika virus.
Preventing Zika virus
The prevention of the Zika virus infection is primarily a protection against mosquito bites. The use of approved insect repellents, sleeping under mosquito insecticide-treated nets, wearing appropriate clothing that covers arms, hands, legs, and exposed body parts should be followed strictly again and again.
Other preventive measures include the use of condoms if you will have sex with someone who just returned from an endemic region. If you are pregnant, try to delay or postpone travels to anywhere marked as risky for you and your baby.
How is Zika virus diagnosed
Diagnosis of Zika virus infection in an individual is based on taking a detailed history that includes symptoms, travel history, and laboratory tests.
Symptoms of Zika virus is quite similar to other flaviviruses like dengue and chikungunya. Hence, tests are carried out to rule out other viral infections. The tests are directed towards investigating for Zika virus itself or indirectly to confirm evidence of disease caused by the virus.
Blood or urine samples are taken to confirm a Zika virus infection.
The procedure for testing may vary but usually involve two tests:
- Nucleic acid test (NAT) is carried out to detect genetic evidence of the b virus. NAT test can be performed using blood or urine samples or concurrently on both samples.
- Immunoglobulin M (IgM) testing is done to detect the presence of antibodies produced by the body in response to the infection caused by the Zika virus. The body in response to infection produces proteins called antibodies, which are evidence of previous or ongoing infection. This is a blood-based test carried out within four days of onset of symptoms.
Accuracy of testing
No laboratory test is 100% accurate. There are cases of false-negative results, where a laboratory test is showing no infection, and in the real sense, there is an ongoing Zika virus infection.
Making a diagnosis of Zika infection is somewhat complex. Molecular studies for Zika virus exposure is only reliable within the first two to three weeks after exposure. Antibody tests could also be messed up by cross-reactivity of Zika with other similar viruses such as yellow fever and dengue.
There are new rapid tests for Zika, but none is 100% specific for the Zika virus. It is a paper-based test specific for NS1 protect of the virus, and it produces result within twenty minutes.
(Massachusetts Institute of Technology. (2017, September 27). New test rapidly diagnoses Zika: Paper-based diagnostic avoids false positives from Dengue fever and other related viruses. ScienceDaily. Retrieved December 28, 2019 from www.sciencedaily.com/releases/2017/09/170927162021.htm)
What are the reasons for a false negative or positive result
- The result will appear negative if an IgM test is performed earlier when the antibodies to be tested hasn't been sufficient enough to be detected.
- If there is a decline in the level of IgM after a resolving infection, the result will appear negative also, if a NAT test is carried out when the virus is no longer in the blood through the virus may still be present in body fluids like semen.
- An IgM test may appear positive if IgM levels persist even after the infection has resolved or when there is a cross-reaction with other viruses.
Who is to get tested for the Zika virus?
As simple as testing for the Zika virus may seem, everyone is not to be tested. Testing for Zika virus is strongly recommended for the following groups at risk:
- Any individual exposed to the Zika infection through sex or recently traveled to a Zika endemic area presenting with symptoms
- Any pregnant woman who had unprotected sex with a Zika virus-infected person or who just returned from an endemic.
- A pregnant woman believed to be exposed to Zika virus during a recent visit to or just returning from an endemic area.
There are lots of frequently asked questions, especially about current pregnancies in an infected mother, the fate of future pregnancies, infected mothers breastfeeding their babies, prevention and protection from the virus, treatment, endemic regions, and the likes.
There is also a travel guideline available to provide information on areas that are relatively safe for travel even during pregnancy.