SAN FRANCISCO (CBS SF) — A total of eight San Francisco residents have tested positive for Zika virus, according to Department of Public Health officials.

The latest case comes just a week after the San Francisco Health Department declared two additional cases of the virus, and two weeks after three other cases were also announced, making July the month with the highest number of infections reported.

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All of the residents who tested positive for Zika contracted the virus while traveling outside the U.S. Additionally, the virus is not circulating in the city and there is no risk to the public, according to the health department.

The health department is not providing any details about the patients, in order to protect their privacy.

The city’s first case of Zika was reported on March 3, followed by a second case reported on April 22. Three additional cases were then reported on July 15, followed by two other cases last week, with Friday’s announcement being the most recent.

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The Zika virus is spread through mosquito bites and can generally cause mild symptoms in patients, such as fever, joint pain, rash and red eyes. Places where the virus is currently circulating include most of Latin America, the Caribbean and the Pacific Islands.

Women who are pregnant are most at-risk to the virus, as Zika is known to cause birth defects, including microcephaly, a condition that causes babies to be born with abnormally small heads.

There is evidence that the virus can be passed through sexual transmission from men to women and men to men.

Currently there is no vaccine for Zika, however, research is underway.

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