Image source: USDA/Flickr.

You've probably heard by now of Zika virus, a mosquito-borne illness that first made headlines after spreading across Brazil, seemingly overnight. Experts expected the disease to make its way to the United States quickly -- and the most recent data proves they were right.

The quickly unfolding situation has left the government, public health officials, and companies scrambling to develop response procedures and tools to combat the disease in both the short and long term. Here's what you need to know about Zika virus, and the efforts underway at Intrexon (NASDAQ:PGEN), Inovio Pharmaceuticals (NASDAQ:INO), and Sanofi (NASDAQ:SNY).

This isn't the next Ebola

The disease poses a very serious public health threat (more on that below), but this isn't the next Ebola. Most individuals who are infected with Zika virus will never know they have it, will never get sick enough to go to the hospital, and will return to normal health in a matter of days or weeks after mild symptoms such as fever, rash, or joint pain. Compare that to recent Ebola outbreaks that had mortality rates as high as 70%, as well as different modes of transmission.

While most people who become infected will never even take a sick day, Zika virus poses an extremely high risk to pregnant women, who can give birth to children with serious lifelong birth defects in a condition known as microcephaly. The seriousness of the situation, and difficulty officials face in controlling any potential epidemic, were best summarized by Dr. Anne Schuchat, the principal deputy director at the Centers for Disease Control, who said: "The reality is one bite, and if you're pregnant, your baby might be harmed. That's a phenomenal problem."

Zika virus is already in the United States

Dr. Schuchat and others at the CDC estimate that thousands of people in the United States are, or have been, infected with Zika virus. These are all individuals who returned to the country after traveling to regions overseas -- including Puerto Rico -- that have active virus transmission -- meaning no one in that estimate became infected while in the United States.

However, this is still worrisome. Infected individuals who return home and are still fighting off the virus -- whether they show symptoms or not -- have the potential to start local outbreaks, which could quickly snowball into an epidemic. That's because Aedes aegypti, the mosquito that most commonly spreads Zika virus, flourishes throughout the lower 48 states, from the Florida Keys to the state of Connecticut.

Estimated range of Aedes aegypti. Image source: CDC.

Funding is still uncertain

In February, President Obama called for $1.9 billion in funding to prepare for and combat Zika virus during the mosquito-friendly spring and summer months. But government officials are still squabbling over how much funding is needed and where it will come from.

One of the more promising routes to funding is the Zika Response Appropriations Act of 2016, which seeks to redirect $622.1 million in unused funds from the 2014 Ebola outbreak and Department of Health and Human Services. If approved, the funding would cover the remainder of the 2016 fiscal year that ends in September.

While important to companies developing solutions to Zika virus, the full $622.1 million is not available for Intrexon, or Inovio, or Sanofi alone. For instance, the bill proposes $120 million in funding for the CDC, but it may be allocated for disease surveillance, public education, mosquito-control efforts, laboratory overhead, and other activities. That makes it difficult to gauge how much may be available for any specific technology or company. Nonetheless, here's a general breakdown of the proposed funding by application:



                    Funds Available


Vector control (mosquito control)

$120 million (CDC), $100 million (State Department)

Inovio, Sanofi

Vaccine development

$230 million (National Institutes of Health), $103 million (BARDA)

Source. The U.S. House of Representatives Committee on Appropriations.

It's important to remember that these vaccine-development funds could go to internal efforts at the NIH, or academic teams at universities, in addition to Inovio and Sanofi. Similarly, vector-control funds could go to companies such as Intrexon and MosquitoMate, or to pay for insecticide applications.

Vaccines are years away

Large pharmaceutical companies are hesitant to dive into Zika vaccine development for various reasons. For one, researchers have largely neglected to study the virus, which means we have a lot of work to do before fully understanding it. That could increase the already-lengthy time it takes to bring a vaccine to market.

Some companies estimate commercialization could be 10 to 15 years away, although as fellow Fool Keith Speights notes, Inovio could potentially apply for approval after Phase 2 testing. For now, it has yet to begin Phase 1 trials in humans, putting that potential decision at least several years away.

Another major source of hesitation on the part of vaccine developers stems from the potential for large populations of humans to develop natural immunity to Zika virus within the next five to 10 years -- about the time it takes to develop a vaccine. That's according to comments from Moncef Slaoui, Chairman of Vaccines at GlaxoSmithKline, which has yet to announce its decision on vaccine R&D.

There's no silver bullet

As is often the case, there's no silver bullet for combating Zika virus. Public health officials will deploy a range of tools in the short and long term. In the near term, tools will focus on controlling mosquito populations by spraying insecticides, releasing Intrexon's genetically engineered mosquitoes, and releasing MosquitoMate's mosquitoes that are infected with larvae-targeting bacteria. Educating individuals and mobilizing response teams will play another key role in protecting public health.

In the long term, tools will focus on continuing to control mosquito populations -- hopefully, we learn a thing or two from deploying new technologies in the next few years -- and developing and distributing vaccines. We may even decide that completely eradicating certain types of mosquitoes capable of transmitting devastating diseases (including Zika virus, yellow fever, malaria, and chikungunya) is in our best interest as a species... but that's a different discussion.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.