So the questions are:
- Is the Zika virus "relatively new"?
Zika virus is an emerging mosquito-borne virus that was first identified in Uganda in 1947 in rhesus monkeys through a monitoring network of sylvatic yellow fever. It was subsequently identified in humans in 1952 in Uganda and the United Republic of Tanzania.
To compare, Malaria has been around since humans have - although it was only discovered in 1880.
It has also been prevalent in Africa for a while - so it's not a "discovered last year" issue.
- Is it true that the Zika virus is prompting worldwide concern by health officials?
Yes and No. Yes, they're concerned, they're calling this meeting. No, because the meeting hasn't happened yet:
WHO Director-General, Margaret Chan, will convene an International Health Regulations Emergency Committee on Zika virus and observed increase in neurological disorders and neonatal malformations.
The Committee will meet on Monday 1 February in Geneva to ascertain whether the outbreak constitutes a Public Health Emergency of International Concern.940s and has since become endemic in parts of Africa.
They won't decide for another two days.
As Dr Margaret Chan, she is "Asking the committee for advice on the appropriate level of international level of concern".
- Is it true that "the WHO estimates 3 million to 4 million people across the Americas will be infected"?
I can find no statement from WHO.int that contains "million" in referece to the number of expected infections. That's not to stop The BBC, The Independent, Reuters, The Guardian, CNN, and more from reporting the statement "3 to 4 million cases" - normally attributed to Marcos Espinal.
- Is the number of people potentially infected large compared to other tropical diseases?
WHO says that
There are between 1.4 million and 4.3 million cases a year, and as many as 142 000 deaths [from Cholera].
According to the latest WHO estimates, released in September 2015, there were 214 million cases of malaria in 2015 and 438 000 deaths.
finnaly, TB (Tuberculosis)
In 2014, 9.6 million people fell ill with TB and 1.5 million died from the disease.
We don't have numbers of people who will get infected (and if you assume 3 - 4 million, no timeframe). But the number of people in affected countries is around 3.34 Billion. Compare that to the 3.2 Billion at risk from malaria.
Map and Population Data.
These questions have since been removed from the original question post
- Is there "no medicine to treat the infection"?
As WHO.int says, "There is no specific treatment or vaccine currently available".
- What percentage of Zika virus victims are estimated to conceive babies with microcephaly?
Note that Zika doesn't necessarily cause it:
Dr Aylward: Association between #Zika and microcephaly or Guillain-Barrè syndrome is not necessarily causation #ZikaVirus
- Do other mosquito-born diseases cause birth defects
and how does their threat level compare to the Zika virus?
I can't find anything caused by mosquitoes. Fleas / Ticks might do something.
- Is there a reason for an average person living in an area infected by the Zika virus to worry about it more than other diseases?
No. The "average" person is not pregnant. There are 7,256,000,000 humans, and only 49.75% are female.
Of that 57.32% are of childbearing age, so just 2,069,171,752 could be pregnant. The number of pregnant women can be estimated from the birth rate - 256 worldwide births per minute. Each of those women were pregnant for 9 months, and there are 394,200 minutes in 9 months, suggesting 100915200 pregnant women at any given minute. That's about 4.87% of fertile women, or 1.39% of people. No, most people are not pregnant women.
Numbers from CIA "The World Factbook"
The other possible issue is Guillain–Barré syndrome. As CDC says:
Guillain-Barré syndrome (GBS) is a rare disorder where a person’s own immune system damages the nerve cells, causing muscle weakness and sometimes, paralysis. These symptoms can last a few weeks or several months. While most people fully recover from GBS, some people have permanent damage and in rare cases, people have died.
We do not know if Zika virus infection causes GBS. It is difficult to determine if any particular pathogen “caused” GBS. The Brazil Ministry of Health is reporting an increased number of people affected with GBS. CDC is working to determine if Zika and GBS are related.
Right now, there are no proven links to serious issues, and even if these are proven, very few people are vulnerable.
About 1 in 5 people infected with Zika will get sick. For people who get sick, the illness is usually mild. For this reason, many people might not realize they have been infected.
The most common symptoms of Zika virus disease are fever, rash, joint pain, or conjunctivitis (red eyes). Symptoms typically begin 2 to 7 days after being bitten by an infected mosquito.