First, and this is wicked cool, there’s a lab in Wisconsin that has infected 7 monkeys (including 1 pregnant female) with Zika virus and they are posting their results in real-time online. The group is called Zika Experimental Science Team (ZEST) and you can track the progress of their monkeys here. Although this is a small sample size and may not reflect the exact course of infection in people, it is so important to get this data in a fixed and controlled manner so we can generate hypotheses and learn more about the virus, including where in the body it can go.
One hypothesis that will be tested by the ZEST team is whether Zika virus infected monkeys are protected against subsequent Zika infections. This is called immunological memory–the ability of your body to remember an infectious pathogen or vaccine and respond more quickly and vigorously if you see it again. If the monkeys have immunological memory to Zika virus, it may suggest that people do too, which would be one win for humanity against this relatively new opponent.
There have also been some recent updates in the ways people get infected with Zika virus, what virologists call modes of transmission. The primary way is still through mosquito bites, but it is becoming clear that people can transfer the virus directly to others through sex. The virus is definitely present in semen, so it can be transferred from an infected man to any sexual partner. It is not clear yet whether an infected woman can transfer the virus to a sexual partner, but it’s best to use condoms, even on shared sex toys, if any partner has been to a Zika virus endemic area. Check out the CDC’s updated information and map of areas with active Zika virus transmission.
It is also apparent that Zika can be transmitted through blood. That’s how it gets into the mosquitoes in the first place, but direct blood transmission is also a possibility. There have been zero cases of transmission via blood transfusion in the U.S, but there have been cases in Brazil. The virus has been found in blood of infected people and the monkeys in the ZEST study, so it is likely that as long as it is floating around in the blood, it can be passed to others. The FDA has issued a statement requesting individuals who have returned from areas of active Zika infection (again, see map) to defer blood donation, but testing of the blood for Zika virus is not yet part of the screening process. Regardless, if you require a blood transfusion, you are in no shape to deny it because of this risk. And as always, don’t share needles.
The virus has also been isolated from saliva and urine of the ZEST monkeys and a patient (see the case report here). Whether Zika virus can be transmitted to others through saliva or urine is not yet known.
As the weather warms toward spring, remember that our best weapon against Zika virus is bug spray–use it.