SAN FRANCISCO (CBS SF) — With hundreds of Zika virus cases already detected in the United States and American territories, Senate Democrats are seeking passage of emergency funding despite what they describe as significant resistance from Republicans.

A Senate bill seeking emergency funds to fight the virus was introduced in Congress on Monday, but as temperatures across the country begin to rise, causing the threat of Zika to loom large, the temperature of the political debate over how to take action against the potential health crisis is also climbing.

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U.S. Senator Dianne Feinstein (D-California) and over 40 other Democratic senators penned a letter to Senate Majority Leader Mitch McConnell (R-Kentucky) and Senate Appropriations Committee Chairman Thad Cochran (R-Mississippi) last week calling for the immediate passage of the President’s emergency supplemental funding request of $1.9 billion for prevention and treatment of the Zika virus outbreak.

Obama asked Congress on February 22 to set aside $1.9 billion to combat the spread of the virus.

Feinstein said in a statement that the letter comes two months after Congressional Republicans “failed to respond to the Administration’s emergency funding request, even though more than 800 Americans in 40 states, the District of Columbia and three U.S. Territories, including 89 pregnachartoftheWeek_040616finalnt women, have already been infected by the virus.”

The Center for Disease Control and Prevention (CDC) has confirmed a link between Zika virus infection during pregnancy and severe birth defects like microcephaly. Scientists are continuing to investigate a possible link between the Zika virus and autoimmune disorders.

Zika virus cases have been detected in San Francisco, as well as other parts of the Bay Area and California, but those cases were reportedly all contracted during travel abroad, according to the CDC.

However, 500 Zika virus cases presumably from local mosquito-borne transmission have already been reported in the American territories: Puerto Rico, the U.S. Virgin Islands and American Samoa, according to the CDC.

The letter to McConnell and Cochran states that while the Administration has offered $510 million to be transferred away from fighting Ebola and be put toward containing the Zika virus, as suggested by Congressional Republicans, Congressional Democrats say public health officials shouldn’t have to choose between containing the two viruses. The letter states:

“While we do not yet know how far north the mosquitoes that transmit this virus can travel, nor the extent of the health complications that people infected with this virus face, we do know how to prevent its spread. As we have stated before, we must work to improve vector control, improve women’s access to contraceptives and family planning, and accelerate the development of treatments – including a vaccine. We must protect pregnant women and children from this devastating disease.‎”

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Congresswoman Nancy Pelosi (D-California) commented Monday that Republicans are “inexplicably” blocking access to resources that could help stop the spread of the Zika virus. She released a statement explaining that:

“Twice, Republicans on the House Appropriations Committee have blocked emergency resources to fight the Zika virus – even voting down emergency resources on the same day the CDC confirmed that the Zika virus causes irreversible brain defects. Republicans’ inaction in the face of the threat that the Zika virus poses for millions of Americans this summer, including more than two million pregnant women, could have devastating consequences.”

House Appropriations Committee Chairman Harold Rogers (R-Kentucky) urged the Administration back in February to pursue the use of unobligated Ebola funds to meet the immediate needs of response to the Zika outbreak, including more than $1.4 billion from the Department of Health and Human Services, and additional unobligated, unprogrammed funds from the U.S. Agency for International Development.

In a statement released last week, Rogers said:

“The Administration continues to delay response efforts by refusing to provide basic budgetary information to Congress on their Zika funding request…we remain committed to seeking out and using existing funding that has been sitting unspent and unneeded in order to direct these dollars to critical Zika response efforts that are necessary right now…We are committed to doing what it takes to stop this devastating disease, both now and as needed in the future.”

However, the White House sees the issues differently.

White House director of management and budget Shaun Donovan explained earlier this month that only with the full amount of requested emergency funding would the U.S. be able to adequately carry out activities to stop the spread of the Zika virus, such as the testing and manufacturing of vaccine candidates beyond early stage clinical trials and development of platform technologies for vaccine candidates.

Donovan said that without the funding, the U.S. would be forced to delay mosquito surveillance and control activities prior to the summer, and prior to the start of the rainy season in Central America and the Caribbean.

He said contracting with manufacturers for faster, more accurate diagnostic tests and fast point-of-care diagnostics, would likely also be delayed if funding is not approved.

The World Health Organization warned Monday of the potential for a significant increase in Zika virus infections as summer arrives in the northern hemisphere, along with virus-transmitting mosquitoes.

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By Hannah Albarazi – Follow her on Twitter: @hannahalbarazi.