At least 66 people have been diagnosed with the Zika virus in the United States, the US Centers for Disease Control and Prevention (CDC) said Wednesday.
The CDC, a federal agency and the leading national public health institute of the United States, said that as many as 5 cases were reported on Tuesday.
Delaware, Indiana, Ohio, Pennsylvania and Tennessee were the five states that reported their first cases of people diagnosed with Zika virus on Tuesday.
In total, 19 states and Washington, DC, have reported cases of the virus which is linked with a surge in cases of microcephaly -- an untreatable condition in which babies are born with abnormally small head and undeveloped brain.
Zika is usually spread by mosquitoes, but can also spread through unprotected sex, blood transfusions or rarely from mother to child around the time of birth. There's no vaccine or treatment.
Last week, Texas health officials reported the first known case of Zika virus transmission in the US on Tuesday, where a Dallas man contracted the virus after sexual contact with someone who had traveled to Venezuela.
Initially, Zika had been thought to be spread by the bite of the Aedes genus mosquitoes and its transmission through sexual contact is an alarming development.
The virus has been reported in more than 30 countries and according to experts, with the pace at which the virus is spreading, especially in the Americas, more cases of Zika-linked birth defects will soon surface in other countries.
WHO has warned that the virus is "spreading explosively" in South America and could infect as much as 4 million people in the Americas this year.
US President Barack Obama has called on the Congress to provide over $1.8 billion in emergency funds to respond to the Zika virus in the United States and abroad.
This is while, US health officials say it will be years before a vaccine can be developed and be made widely available for the Zika virus.