Only by understanding the Zika virus and its transmission routes can we better prevent and treat it!

Author: Jiang Rongmeng, Chief Physician, Beijing Ditan Hospital, Capital Medical University

Reviewer: Wang Linghang, Chief Physician, Beijing Ditan Hospital, Capital Medical University

The Zika virus was first discovered in 1947. Previously, people's knowledge of it was very limited. There were mainly a small number of cases in Africa. Later, it spread to Asia and then to South America from Asia in 2014. The main country of the outbreak was Brazil.

From 2015 to early 2016, millions of cases of Zika virus infection were found in Brazil. During that year, the number of new cases of microcephaly in newborns increased twenty times compared with the previous decade. People realized that the Zika virus was not that simple.

On February 1, 2016, the World Health Organization declared the Zika virus a public health emergency.

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1. How is Zika virus transmitted?

The Zika virus is mainly transmitted by insects, the most important of which is the Aedes aegypti. The distribution of this mosquito in China is very limited. According to monitoring, the Aedes aegypti is only found in about four places in China. The first is southern Taiwan, the second is the Leizhou Peninsula in Guangdong, the third is Hainan Island, and the fourth is Xishuangbanna in Yunnan. Basically, they are all in the southernmost part of China.

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For example, if someone is infected with the Zika virus and becomes ill in a place where the Aedes aegypti mosquito exists, if the Aedes aegypti mosquito bites him and then bites someone else, the virus may be spread.

In areas where there are no Aedes aegypti mosquitoes, if a patient infected with Zika virus is introduced, the risk of transmission is very, very low because this mosquito does not exist.

In addition to the mosquito transmission route, the virus can also be transmitted between people, mainly in several situations. The first is sexual transmission, whether between the same sex or the opposite sex, because the Zika virus can exist in male semen and female vaginal secretions. The second is blood transfusion. If you are infected with the Zika virus and donate blood, the blood can also be transmitted to others.

In addition, Zika virus cannot be transmitted through daily life contact, nor can it be transmitted through the air, nor can it be transmitted through close face-to-face talking or shaking hands.

2. What are the possible symptoms of Zika virus infection?

After being infected with Zika virus, 80% of people have no clinical symptoms and no discomfort, which is called latent infection.

Only 20% of people may have clinical symptoms, and the symptoms are generally mild, such as fever, usually around 37 to 38 degrees, rarely high fever; headache, muscle aches, bone and joint pain; and some may have conjunctivitis and rashes. Patients can tolerate it, it does not affect their daily life and work, nor does it affect eating or sleeping. It can heal itself in about five to seven days, so sometimes people often say that you don't have to worry too much about being infected with the Zika virus, it's nothing serious.

After some young adults and children are infected, the first symptom may be muscle weakness, which can cause respiratory muscle paralysis in severe cases. If there is no endotracheal intubation or machine ventilation support, they may die from respiratory muscle paralysis, which is called Guillain-Barré syndrome. This is the most serious symptom, but it is very rare.

The biggest threat of Zika virus is to the fetus. When pregnant women are infected with Zika virus, it will cause certain risks to the fetus, such as microcephaly. After the child is born, the head circumference is smaller than that of normal children, and the intelligence will also be affected. Some pregnant women infected with Zika virus will cause intrauterine fetal death and miscarriage.

3. How to treat after being diagnosed with Zika virus infection?

After being infected with Zika virus, the virus will first be present in the body. The simplest way now is to confirm the diagnosis by testing for viral antibodies. Another way is to confirm the diagnosis by testing for viral nucleic acid.

Most symptoms after infection with Zika virus are mild and can heal on their own. There is currently no effective antiviral drug for treatment. The main treatment is symptomatic. For example, if the body temperature is high, antipyretic treatment can be used. If neurological complications occur, supportive treatment is given. If a pregnant woman is infected, there will be a very detailed fetal monitoring system, including fetal assessment to predict the child's future outcome, and professional doctors will give some advice.

Generally speaking, as long as there are no neurological complications, adults who are infected will not have any sequelae. After recovery, they will be the same as normal people and the rash will completely disappear. If Guillain-Barré syndrome occurs, some people may have sequelae, such as affected muscle strength.

Although the symptoms disappear after infection with Zika virus, the virus can exist in the body for a long time. For example, it can exist in male semen for 188 days. As long as there is the virus in the body, it may be a source of infection and can be transmitted to others. After infection, women should postpone pregnancy for half a year, because the virus can infect the fetus through the placenta, causing adverse clinical consequences.