Scientists at the Centers for Disease Control and Prevention (CDC) have concluded, after careful review of existing evidence, that Zika virus is a cause of microcephaly and other severe fetal brain defects. In the report published in the New England Journal of Medicine, the CDC authors describe a rigorous weighing of evidence using established scientific criteria.
Zika virus disease is spread to people primarily through the bite of an infected Aedes species mosquitoes. It can also be spread from mother to child, through sexual contact and through blood transfusion. There is an abundance of helpful up to date information about Zika on the CDC website.
Some infected people will get symptoms (fever, rash, joint pain, or red eyes) for up to a week but most people won’t even know they are infected. Estimates are that 4 out of 5 persons infected will not show symptoms, although they will be infectious and can carry the disease to other areas that have Aedes mosquitoes or transmit it to others through sexual contact or blood transfusion.
Public health authorities throughout the region have begun reporting travel related (individuals who traveled to known area with Zika) as well as locally acquired cases of Zika (no travel to infected areas). The graphic below displays the countries that have reported cases of Zika.
However, it is known that some countries in the region lack the public health infrastructure to conduct or fund testing, or may not submit results to CDC/WHO. It is wise to consider every country that has Aedes mosquitoes as having Zika infected mosquitoes.
The Zika virus can also be spread during sex by a man infected with Zika to his partners. In known cases of sexual transmission, the men had Zika symptoms. From these cases, CDC determined that the virus can be spread when the man has symptoms, before symptoms start, and after symptoms end. The virus can stay in semen longer than in blood. There are many important unanswered questions about the sexual transmission of Zika, presented on the CDC website.
For further information about Zika transmission and blood transfusion see: http://www.cdc.gov/zika/transmission/blood-transfusion.html
There is no vaccine or medicine for Zika. Everyone in the region should take mosquito bite prevention actions, presented by the CDC.
Those who are pregnant, become pregnant, or are planning to become pregnant, should exercise special caution. Important information for this group is available on the CDC site.
Given the patterns exhibited by similar viruses (dengue and chikungunya), there is concern that US states will begin to show locally acquired cases of Zika as spring/summer temps allow mosquito populations to expand.
Those in the region who are planning to travel to areas that have Aedes mosquitoes, or who have guests who will do so, should take care to understand the best available information on Zika.