1. What is the Zika virus?
A new tropical infection of the Western Hemisphere. The Zika virus is a mosquito-borne infection related to dengue fever, yellow fever and West Nile virus. Although it was discovered in the Zika forest in Uganda in 1947, it is common in Africa and Asia, but had not begun to spread widely in the Western Hemisphere until last May, when an outbreak occurred in Brazil.
So far, almost no one on this side of the world had ever been infected. Few people here have immune defenses against the virus, so the same is spreading rapidly. Millions of people in tropical regions of the Americas may now be infected.
However, for most, the infection does not cause symptoms and does not lead to any lasting damage. The scientific concern is focused on women who became infected during pregnancy and those who develop a temporary form of paralysis after exposure to the Zika virus.
2. How does a mosquito transmit Zika?
Only female mosquitoes sting people: they need blood in order to lay eggs. They get the virus in their blood. It moves from your gut through your circulatory system to your salivary glands and is injected into your next human victim. Mosquito saliva contains proteins that prevent blood clotting. When a mosquito bites, it first injects saliva so that the blood of its prey does not clog its spicy “needle”.
3. What areas can Zika achieve?
Zika is transmitted by mosquitoes of the genus Aedes, which can breed in a container of water as small as a bottle cap and usually sting during the day. The mosquito is common in the United States only in Florida, along the Gulf Coast, and in Hawaii – although it has been found as far north as Washington, DC, in hot climate. In Brazil, the mosquito is very common.
The Asian tiger mosquito, Aedes albopictus, is also known to transmit the virus, but it is not as efficient.
4. Can the Zika virus be sexually transmitted?
Experts believe that the vast majority of all Zika infections are transmitted by mosquitoes, not sex. As of February 2, there were only three reports suggesting sexual transmission.
- In 2008, a scientist who studies malaria in Africa returned to Colorado and apparently ended up infecting his wife before developing the symptoms in himself. Both had fever, rash, and headaches. A year later, the blood tests, which had been frozen, revealed that both had had Zika.
- In 2013, the live virus was found in the semen of a 44-year-old man; if he infected someone, nobody knows.
- In early February, Texas health officials announced that a traveler who had returned to Dallas from Venezuela had apparently been infected by a sex partner.
In the first two cases, the men had genital pain and blood in the semen, which suggests that their testicles or prostate had been infected. Details about the third case were not disclosed.
Based on these reports, the CDC issued new preliminary guidelines suggesting that pregnant women avoid contact with the semen of men who have recently returned from areas with Zika transmission. Men returning from these regions should consider using condoms, the agency said.
The authorities do not provide guidance on how long to do so. British health officials have suggested using condoms for at least 28 days.
There are still many unknowns, including:
- Can a woman pass the virus on to men through sex? can it be passed via anal, vaginal, oral or any other form of sex?
- Does a man have to have blood in the sperm to be infectious? Is he infectious before the blood appears?
- If there is no blood, does he have to have Zika symptoms like fever and rash to transmit the virus? How Long Does a Man Remain Infectious?
5. How can Zika cause brain damage in children?
The possibility that the Zika virus causes microcephaly – Small heads and often damaged brains – arose only in October, when doctors in northern Brazil noticed an increase in babies with the disease.
It may be that other factors, such as simultaneous infection with other viruses, are contributing to the increase; researchers may even find that the Zika virus is not the main cause, although circumstantial evidence now suggests that it is.
It is not known how microcephaly became an outbreak in Brazil. About three million babies are born in Brazil every year. Usually about 150 cases of microcephaly are reported, and Brazil says it is investigating about 4,000 cases. However, cases usually increase when people are alerted to a potential health crisis.
6. Is there treatment?
The CDC does not recommend a specific antiviral medication for people infected with the Zika virus. The symptoms are mild – and generally only require rest, food, and other supportive care.
7. Is there a vaccine? How should people protect themselves?
There is no vaccine against the Zika virus. The efforts to make one just started, and creating and testing a vaccine usually takes years and costs hundreds of millions of dollars.
Because it is impossible to completely avoid mosquito bites, the CDC has advised pregnant women to avoid going to regions where Zika is being transmitted, and has advised women to think about getting pregnant, to consult doctors before going.
Travelers to these countries are advised to avoid or minimize mosquito bites by staying in air-conditioned rooms or sleeping under mosquito nets, using insect repellent at all times and wearing long pants, long sleeves, shoes and hats.
8. Outside Brazil, has any outbreak of Zika ever been linked to microcephaly?
Last November, authorities in French Polynesia reinvestigated an outbreak of Zika that lasted from October 2013 to April 2014. They reported finding an unusual increase – from about one case per year to 17 cases in 2014-15 – from developing fetuses with “malformations of the central nervous system”, a classification that includes microcephaly.
There were no investigations at the time to determine whether the mothers were infected with the Zika virus during pregnancy. Four of the mothers were tested later and the results indicated that they may have been infected with the virus. Additional research is ongoing, Dr. Musso said.
Source: The New York Times