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- Page 1 – Hello Zika, are you still there?
- Page 2 – Everything over and completely overestimated?
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For a long time, the Zika virus was something like the little harmless brother of the deadly dengue virus. It caused a slight fever, pustules on the skin, a booming head, painful joints, but after a few days of bed rest it was over. At the end of 2015 this changed dramatically when Zika suddenly spread rapidly to Brazil. Thousands of children with heads that were far too small, strangely shaped and flattened on the forehead and back of the head were born. The virus had been transmitted from mosquitoes to pregnant women via their blood into the uterus and into the cells of the unborn children, where it had caused the malformations.
Starting in Brazil, the virus continued to jump, with 28 countries in Latin America and the Caribbean already infected by early February 2016. When the World Health Organization declared a global health emergency on February 1, 2016, the virus mutated into a supposed threat to the entire planet.
But as fast as the virus came, it seems to have disappeared again: Today – exactly two years later – Zika is almost forgotten. Nothing has remained of the excitement of the past. Only those who look out attentively will find the yellowed signs at airports that warn of the dangers of the virus. What happened?
How big are the tracks Zika left behind?
That’s a hell of a thing to investigate. It starts with the numbers. “No one knows exactly how many people have been infected,” says Jonas Schm >WHO , the Pan American Health Organization (PAHO), referring only to those who have had the typical symptoms. That was almost 600,000 people in North, South and Central America between 2015 and today (PAHO, 2018, pdf). Only 220,000 of them have been laboratory tested for infection. In the majority of Zika patients, however, the infection was asymptomatic and they were unaware of the infection. Researchers therefore assume that more than 1.5 million people were infected in Brazil alone.
zika virus
What is the Zika virus?
Discovered in 1947 by dengue researchers in experimental monkeys – in a forest called Zika in Uganda – the virus was detected in humans five years later. The mosquitoes of the genus Aedes transmit it. At present, this is most frequently caused by the yellow fever mosquito Aedes aegypti. It is found in the tropics and subtropics. However, the virus can also be transmitted to the unborn child during sex, via blood transfusions and via the placenta of a pregnant woman.
There are two lines of the virus: an African and an Asian (Haddow et al., 2012 & Faye et al., 2014). The latter triggered previous outbreaks in Africa, America, Asia and the Pacific region (Enfissi et al., 2016). They were all manageable.
Virologists became aware of the virus from the Flavivirus family in 2007, when more than 100 people fell ill on the Pacific island of Yap in Micronesia. In 2013, the next major outbreak occurred: in French Polynesia, about one tenth of the population got Zika.
Symptoms of the disease
Zika was not known as a serious disease until now. Most people do not even know that they have been infected. Either they don’t get any symptoms or mild fever, skin rash or conjunctivitis. All this disappears after two to seven days.
More problematic are the possible secondary diseases: microcephaly or Guillain-Barré syndrome. The number of newborns with a cranial malformation had increased a few months after the beginning of the Zika epidemic. In April 2016, the US Department of Health and Consumer Protection (CDC) announced that the link between the virus and the malformation had been proven. The CDC researchers published corresponding results in the New England Journal of Medicine (Rasmussen et al., 2016).
Guillain-Barré is a nervous disorder. It usually begins with paralysis of the legs, which then spreads to the arms and face. In connection with Zika, serious cases of this autoimmune disease have frequently occurred.
Treatment
There is still no specific therapy or vaccine available to protect against Zika. However, several vaccine candidates are being tested. Until these are launched on the market, the best precaution is to protect against mosquito bites and to avoid severely affected areas.
Antibody tests can show who was already infected with the virus. However, these tests are costly, and in some cases they are unsuccessful if someone has become infected with the close relatives of the Zika virus, such as Dengue and Chikungunya.
There are also thousands of cases in Southeast Asia, where the small city-state of Singapore alone reported at least 450. Many German travellers to America were also tested positive for the virus after their return, and at least one also transmitted it to his partner during sex (Robert Koch Institute, 2016, pdf).
The virus prefers to infect nerve tissue and cause damage there. In a developing fetus, this leads to brain malformations. The damaged brain does not develop properly and is often smaller than usual. PAHO estimates the number of microcephalos in the whole of America caused by Zika at 3,700, a large proportion of which, around 2,900, have been reported from Brazil. A study by the American Disease Control Agency estimates that one in 20 women infected with Zika during pregnancy gave birth to a child with malformations (CDC: Shapiro-Mendoza, 2017).
“But the zika microcephaly could only be the tip of the iceberg,” says Peter Jay Hotez, head of the National School of Tropical Medicine in Houston, Texas. “There are many other neurological manifestations of a zika infection.” This refers to damage that parents and doctors did not notice immediately after birth: Deafness, hearing problems, epilepsy, but also developmental problems and learning difficulties among older children. How many children are affected is completely unclear, but there are likely to be many thousands.
And even in adults, the infection can leave traces: After infection with the virus, they develop Guillain-Barré syndrome (GBS) more frequently. In this disease, the patient’s immune system seems to be directed against his own nerve sheaths, which is why the nerves gradually fail. Gradually, the paralysis spreads all over the body. Although this is only temporary, it can lead to serious complications such as cardiac arrhythmias and exposure of the respiratory muscles. A Brazilian study shows what doctors had suspected after earlier outbreaks (The Lancet: Cao-Lormeau, 2016): Many of the GBS patients had previously undergone Zika (JAMA Neurology: Da Silva et al, 2017).
Since the beginning of the epidemic in 2015, says Peter Hotez, there has been a great deal learned about the virus. The fact that the WHO declared a global health emergency released a lot of money for research. Nevertheless, many things are still a mystery to the researchers. “It takes,” says Hotez, “a whole generation of child neurologists and child psychiatrists to understand the neurology behind Zika.”