WEDNESDAY, Sept. 7, 2016 (HealthDay News) -- Congress returned to work Tuesday from its seven-week summer break and failed to agree on additional funding to fight the Zika virus.

Federal and state health officials say the funding is needed as the mosquito-borne virus that causes severe birth defects continues to make inroads into Florida.

The Miami area now has 56 documented cases of locally transmitted Zika infection, which causes the birth defect microcephaly that leads to babies born with abnormally small heads and brains.

There have been no reported locally transmitted cases of microcephaly in the continental United States. But thousands of cases have been documented in Latin America and the Caribbean, with Brazil the epicenter of the outbreak.

Health officials say it's also becoming increasingly clear that the Zika virus can be transmitted through sexual activity.

President Barack Obama in February asked for $1.9 billion in emergency spending to fight Zika.

The Republican-controlled House of Representatives offered $1.1 billion in June, but it came with the provision that none of the money could be given to Planned Parenthood because of that group's endorsement of abortion. Democrats have rejected that provision, saying many lower-income women rely on Planned Parenthood for their health-care needs, particularly in Puerto Rico, where Zika infections are becoming widespread.

In a related matter, the World Health Organization (WHO) on Tuesday recommended that all travelers -- male and female, with symptoms or no symptoms -- practice safe sex or abstinence for six months after returning from areas where Zika is spreading.

The United Nations health agency reiterated that mosquito bites are still the primary means of infection with the virus. The virus has also been linked to neurological complications and Guillain-Barre syndrome, which can cause temporary paralysis.

WHO officials said Tuesday's announcement was prompted by new evidence showing that:

  • symptomless males can transmit Zika to female partners,
  • a woman with symptoms transmitted the virus to her male partner,
  • the virus remains active in semen longer than had been thought.

The vast majority of people infected with Zika experience no symptoms or mild ones, such as a fever and a rash. But because of the risk of microcephaly, WHO says men and women returning from areas where Zika infections are ongoing are "advised to wait at least six months before trying to conceive to ensure that possible virus infection has cleared."

Last week, health officials reported that in areas experiencing a Zika outbreak, there will likely be an accompanying increase in cases of Guillain-Barre syndrome. That finding strengthened the suspected link between infection with the virus and the syndrome, which causes temporary paralysis in its victims.

Public health experts in the United States say that additional Congressional funding to fight Zika is critical because Gulf Coast states, where the Aedes mosquito that transmits Zika mostly lives, is only halfway through peak mosquito season. There's a high risk that Zika could start circulating in cities like New Orleans or Houston, experts say.

With more than 50 cases of locally transmitted Zika in the Miami area, U.S. health officials are urging women who are pregnant or thinking of becoming pregnant to take health precautions. The U.S. Centers for Disease Control and Prevention is advising that pregnant women avoid traveling to those areas of Miami where infections are occurring to reduce their risk of contracting Zika.

The CDC also is advising pregnant women not to travel to an area where active Zika transmission is ongoing, and to use insect repellent and wear long pants and long-sleeved shirts if they are in those areas.

More information

The U.S. Centers for Disease Control and Prevention provides more information on mosquito-borne diseases.

This Q & A will tell you what you need to know about Zika.

To see the CDC list of sites where Zika virus is active and may pose a threat to pregnant women, click here.