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September 15, 2017
Zika Myth of the Week
Myth: After Zika symptoms go away, the infected person cannot spread the virus anymore. 

This is a myth and is not correct!

Truth: Many people infected with Zika - about 4 in 5 - will have no symptoms. 
[ Source, Source]  

Even when no symptoms are present, Zika may still be transmitted. For example, such an incident is reported occurring in a French couple without symptoms, published in  Eurosurveillance

Zika can be found in blood for about one week after infection. The virus can be spread to mosquitoes if a mosquito bites the infected person during this time period. This mosquito will then become infected and can spread the virus to other people by biting them. An example of this is shown in Joyce's story below. 

Joyce's Story
Joyce traveled to Latin America and became infected with Zika virus. She returned home to Arizona. In her area, there are  Aedes mosquitoes which are capable of transmitting Zika virus. A mosquito bites Joyce and becomes infected with Zika virus. The same mosquito bites her son and he becomes infected although he did not travel with his mom. 

Zika can also be transmitted  through sexual activity. More research is needed to determine exactly how long Zika can remain in the fluids which may be exchanged during sexual activity, but it is known that Zika virus can remain in men's semen for longer periods of time. 

Men are advised to avoid sexual activity or use condoms for at least 6 months after symptoms or after returning from an area with risk of Zika (if no symptoms develop). Women are recommended to follow the same advice, but only for 8 weeks. These recommendations are intended for couples not currently trying to conceive. Couples interested in becoming pregnant should talk about options with a healthcare provider. 

Pregnant women are advised not to travel to areas with risk of Zika. Pregnant couples should use condoms or avoid sexual activity for the entire pregnancy if either partner may have been exposed to Zika virus by living in, or traveling to, an area with risk of Zika virus. 

Since Zika symptoms, when they occur, typically last only a few days to a week, it is clear that Zika virus can be transmitted after symptoms have gone away. 

Zika 101

Learn the TOP FIVE things everyone should know about Zika  HERE
NIHB Resources
Learn more about Tribal Zika Response and Planning at the NIHB Zika Hub

Did you know NIHB can offer technical assistance related to Zika planning? If you are looking for additional resources or need assistance, please EMAIL NIHB

NIHB main website can be accessed HERE

Have questions? Need assistance? Click here to email NIHB staff 

In This Newsletter
Zika 101

Zika Myth of the Week
-When, and for how long, can an infected person spread Zika? (sidebar)

Zika Information

-Zika and workers: understanding and reducing risk - protect yourself on the job and protect your employees
Zika Information
Zika and Climate Change
Did you know that climate can impact Zika? Climate can affect w here mosquitoes (and other vectors) live and what diseases they carry. Climate can cause health impacts in the United States or in other countries. Global impacts can also affect American people - for example, because of trade or travel. 

This map in the June 30th Zika newsletter shows where Aedes aegypti mosquitoes (the type that best transmit Zika) may be found in the US. Mosquito populations may spread as temperatures become warmer and wetter

The Atlantic summarizes part of a 2005 paper published in the New England Journal of Medicine as:  "they [mosquitoes] bite more, breed more, and spread more disease" [when climate changes]. [ Source ]
Jacobsen, a global health professor at George Mason Univeristy who was also quoted in The Atlantic, says that Zika probably did not arrive in the Americas because of climate change. However, she believes that climate plays a direct role on Zika's impact now that it is here. "Changes in temperature, precipitation, and humidity can alter how long the mosquitoes live, how often they bite, how many offspring they have, and how quickly a virus reproduces inside an infected mosquito, and each of those changes can mean more humans are exposed to mosquitoes," she states. [Source]

Learn more about climate effects on health, including vector-borne diseases like Zika, and what you can do to reduce environmental harm. Resources and information are available from Centers for Disease Control and Prevention (CDC) HERE and from the World Health Organization (WHO) HERE
Zika and Workers: Understanding and Reducing Risk
Some people may be at greater risk of Zika virus infection because of their jobs. 

Images from Centers for Disease Control and Prevention (CDC)

This includes people who:
  • Work outdoors and may be exposed to mosquitoes
  • Travel for work and go to areas with risk of Zika 
  • Work in healthcare or laboratory settings and may be exposed to people with Zika, infected samples, contaminated mosquitoes, or virus cultures
Zika information for all workers is available from Centers for Disease Control and Prevention (CDC) and from the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). View CDC information HERE and OSHA/NIOSH information HERE 

Fact sheets are available with information for  outdoor workers, cruise line employees, business travelers, and healthcare and lab workers. Additional online information is also available for healthcare workers and laboratory workers

should also view this information to learn how to protect and train their employees. 
Zika News
Why so Few Zika Cases this Year? Learn Why, Learn About Herd Immunity, and Learn Why You Should Still be Ready

Many people remember the outbreaks global Zika outbreaks in 2015-2016 and recognize that the number of cases - and the hype - have died down. 

The image below shows data from Central America, the Caribbean, and South America. The graph shows the number of Zika cases in each area over the 52 weeks of the year. Globally, the case numbers spiked in early 2016. 

Zika cases in the Caribbean and South and Central America
Image from Pan American Health Organization (PAHO) & World Health Organization (WHO)  HERE, using data from individual countries and territories 

Last month, the August 11 Zika newsletter addressed the myth that Zika is no longer a threat (in Myth of the Week sidebar).  Although Zika may have decreased, one major reason is  
herd immunity. 

The New Yorker recently published an article discussing some reasons for the decline of Zika, including herd immunity and climate change, which can bring Zika to more northern regions without herd immunity. (Herd immunity will be discussed below and climate change was also discussed in this newsletter's Zika Information section).   Read the New Yorker article  HERE

What is herd immunity? 

Imagine this is a population, below: 

None of these people have ever been exposed to Zika virus. Zika is a new, emerging disease that has not yet come to their part of the world. 

The virus arrives for the first time and one person gets infected (shown in green). Remember, many people who have Zika will not have symptoms, so the person may not even know that he or she is infected. 

Mosquitoes bite the infected person and become infected too. They spread Zika by biting other people (shown with yellow arrows). Those people become infected.  Zika can also be spread through sexual activity. The infected person also spreads Zika through sex (shown with the orange arrow). Now several people are sick. 

It is especially easy to spread Zika in areas like South America because many people live in close quarters and do not have screens or air conditioning. In some of these countries, condoms - used to prevent sexual transmission of the virus or delay pregnancy to prevent Zika-related birth defects - may be expensive or illegal. Some women may also face other barriers such as lack of adequate sex education and little control over their reproduction (including violence against women), or concerns about how to protect themselves while following their personal or religious beliefs. 

These infected people also spread the virus through mosquito bites or sexual activity. 

More and more people become infected. 

These people can also spread the disease to others. 

After a person has Zika, he or she becomes immune to the virus.
Immunity is protection from a disease. Immunity can occur if a person was infected by a disease and can not get the disease again. Immunity can also occur if a person was vaccinated for a disease (although this is not an option for Zika as there is currently no Zika vaccine). 

When Zika virus is no longer in the body, the body's immune system can still "remember" it and can protect against future infection. 

As time goes on, more people in the population become immune. This is especially true of a disease like Zika, since almost everybody will survive. 

These people are shown in white. They cannot spread the disease and they cannot get the disease again. 

The disease continues to spread and more people become sick - and then immune. Eventually, the population may look something like this, with most people immune: 

Remember, white circles represent people who are immune. Blue circles represent people who are susceptible (not immune) to Zika virus. 

When someone else becomes sick, Zika cannot spread very well in the population because most people are immune. There are fewer people to spread the disease and also fewer people to catch it. An immune person will not become infected when he or she is bitten by an infected mosquito or engages in sexual activity with an infected person. 

Only a few people in the community can become infected. The high number of immune people can also protect many of the susceptible people (people who are not immune) from getting sick. A small number of people may still get sick, as shown below. 

When you think of herd immunity, think of a herd of animals - such as sheep, or in this case, people. The "herd" can provide health protection if many people have immunity to a disease - in this case, Zika. 

(Herd immunity is also why it is important to get recommended vaccines and vaccinate your children for other diseases, since this can protect other community members, including those who cannot be vaccinated for medical reasons.)

The images below show an overview of what happened in Latin America. This is one reason that Zika declined. Since no country is in a vacuum isolated from the rest of the world, this is also an important reason for the decrease of Zika in the United States this summer. 

HOWEVER - this does not mean that Zika is no longer a threat. Over time, there will be more young people born and they will be susceptible to Zika virus. Some of the currently immune people will get older and pass away (from unrelated causes). This leads to a population with less immunity and more opportunity for the disease to return. Most people in the United States are not immune, so Zika could also spread more easily in this population - although it is
currently less likely to come to the US because there of herd immunity worldwide.  

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