Zika Virus Outbreak, Spread, Symptoms, Testing, Treatment

Zika virus has been dominating public health news and alerts in 2015 particularly with the South America outbreak. However, with the ease of modern travel, there are cases of Zika virus being reported in various parts of the globe. It is important to note that prior to 2015 there were Zika virus outbreaks in other parts of the world, including the Pacific Islands, Southeast Asia and parts of Africa.

What is Zika virus?

Zike a virus is an RNA flavivirus which is spread to humans through the bite of the Aedes species of mosquitoes. It causes Zika virus disease, also commonly referred to as Zika, and most cases do not cause any serious disease. The symptoms last for a short period of time and resolves spontaneously. In fact it is believed that many cases of Zika goes unnoticed or is mistaken for other common viral infections.

The Zika virus is sometimes associated with an autoimmune condition known as Guillian-Barre syndrome (GBS). This is a condition where the immune system attacks the nerves. It appears that Zika virus may trigger Guillian-Barre syndrome but does not actually cause it. The other major complication is for fetuses as the infection may pass from the mother and cause fetal abnormalities like microcephaly.

Causes and Spread

Zika virus disease is caused by the Zika virus. It is spread through a mosquito bite, from a pregnant mother to her fetus, through sexual contact and via blood transfusions.

Mosquitoes

As with most types of flaviviruses, the Zika virus is usually spread by mosquitoes and enters a human host as a result of a mosquito bite. Uninfected mosquitoes may acquire the virus when they feed on a person who is already infected. The Aedes species of mosquitoes, including Aedes aegypti, Aedes africanus, Aedes luteocephalus, Aedes albopictus, Aedes vittatus, Aedes furcifer, Aedes hensilli, and Aedes apicoargenteus, are the main insect vectors. These mosquitoes also spread dengue and chikungunya.

Pregnancy

A pregnant woman can pass the Zika virus to the unborn fetus and also during childbirth. It has been linked to miscarriages and may also cause a very serious and potentially fatal fetal abnormality known as microcephaly. It can also cause other brain abnormalities, eye and hearing problems as well as growth defects. There is no evidence that Zika virus can be spread through breastfeeding like certain other viral infections.

Sexual Contact

Sexual contact is an uncommon mode of transmission for the Zika virus. The virus remains in semen for longer than it does in blood. Usually transmission occurs when a person is symptomatic but there have been a few reported cases of sexual transmission prior to the symptoms developing and even a short while after the symptoms resolve. Men who are infected or have traveled to high risk areas should use barrier protection or avoid sexual contact to prevent spreading the infection.

Blood Transfusion

The Zika virus can be transmitted through a blood transfusion but this is uncommon. Since most people with Zika do not show any symptoms, it is difficult to pre-screen blood donors apart from checking the history of travel to outbreak areas.

Signs and Symptoms

It is estimated that as many as 8 out of 10 people infected with Zika virus do not show any symptoms. When symptoms are present it is mild and may last anywhere from a few days to a week. These symptoms include:

  • Skin rash
  • Fever
  • Joint pain
  • Muscle aches
  • Conjunctivitis
  • Headaches

Since most of these symptoms are non-specific and a person may not know that they have Zika virus disease. The incubation period of Zika virus infection ranges from 3 to 12 days. This is the period from the time of infection to the onset of symptoms. A person will therefore not be aware of the infection during this time.

Testing for Zika Virus

Diagnosis of Zika virus is made by positive blood test results. The test detects the presence of the Zika virus genetic material and is best perform in the first week of illness. Thereafter other blood tests may be performed to detect antibodies to the virus. As yet there are no over-the-counter or rapid testing methods. Blood samples need to be sent to a laboratory.

There have been reported positive test results for Zika virus in urine samples but the blood test coupled with a history of traveling to an outbreak area is the best way to confirm Zika virus infection.Testing for Zika virus is important because other viral diseases like dengue and chikungunya may also be spread by the same species of mosquitoes.

Treatment and Prevention

There is no specific treatment for Zika virus. The disease is mild and self-limiting. It resolves within a few days to a week. Supportive treatment includes bed rest and plenty of fluids. Acetaminophen may be used for pain and fever but aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) should be avoided in unconfirmed cases of Zika virus. In the event that the infection is dengue, NSAIDs can result in excessive bleeding.

Always speak to a doctor after traveling to an area where there is or recently was a Zika outbreak.

There is currently no vaccine to prevent Zika virus infection. A person who has been infected is likely to be immune to future infections. The key to preventing Zika virus is to avoid being bitten by mosquitoes when traveling to endemic areas. If possible, travel to these areas should be avoided by high risk individuals like pregnant women. Sexual contact should also be avoided or adequate barrier protection should be used by men who are infected.

Tips for Travelers

  • Minimize skin exposure by wearing clothing that covers as much areas as possible. Long-sleeved shirts and long pants are advisable.
  • Air conditioning is advisable to reduce the need for open windows thereby limiting the possibilty of mosquitoes entering a room.
  • Mosquito-proof screens should be used over windows and doors. It is important to check screens regularly for any tears.
  • Mosquito nets should be used over the bed even though the mosquito that spreads Zika mainly feeds during the day.
  • Mosquito repellants can be useful and should be used as directed. It must be avoided for infants under 2 months of age.

References:

  1. emedicine.medscape.com/article/2500035-overview
  2. www.cdc.gov/zika/index.html
  3. www.mayoclinic.org/diseases-conditions/zika-virus/home/ovc-20189269

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