What do zika, ebola, west nile, and avian influenza have in common?

First, all fo them them are viruses, and they cause diseases specific to each virus.

They also all started in foreign third world countries, and they are caused by coming in contact with insects or animals.

ZIKA.  

The Zika virus disease is caused by a virus transmitted mainly by mosquitoes of the genus Aedes.  

Affected individuals may have moderate fever, skin rash (rash), conjunctivitis, muscle and joint pain, malaise, or headache. Normally, these symptoms disappear in 2 to 7 days.  

A scientific consensus has been established that the Zika virus causes microcephaly and Guillain-Barré syndrome. Links with other neurological complications are being studied.  

WEST NILE  

The West Nile virus is transmitted by mosquitoes. It causes a sudden fever, sometimes associated with neurological complications that can be severe in many animal species. Firstly identified in East Africa, the virus has been identified on all continents. Today, it is endemic in some regions.

West Nile virus belongs to the family Flaviviridae flavivirus genus. Migratory birds act as reservoir animals for the West Nile virus. The transmission of West Nile virus is via the bite of mosquitoes of the genus Culex: after biting infected birds, female mosquitoes become competent for transmission of the virus to humans during a blood meal.

Ebola.  

The Ebola virus is responsible for severe fevers and haemorrhages that are often fatal to humans. The case-fatality rate is between 30 and 90% depending on the epidemics and the viral species. The natural reservoir of the virus would be the bat. The Ebola virus was discovered in 1976 during the two outbreaks in Sudan and the Democratic Republic of Congo. Since then, about 20 epidemic outbreaks have appeared in Central Africa. In December 2013, the virus reached West Africa, a region previously unaffected by the disease. In 2014, it causes the largest epidemic known so far. The challenge of current research is therefore to develop a vaccine, treatments and diagnostic tools for the treatment and detection of the disease.  

AVIAN INFLUENZA  

Avian Influenza (AI), caused by Type "A" influenza virus, is a disease which can infect several species of farmed birds (chickens, turkeys, quail, guinea fowl, etc.) as well as ornamental birds and wild birds, some strains resulting in a high mortality rate. This virus has also been isolated from mammals including the man, the rat and the mouse, the mink and the ferret, the pig, the cat, the tiger and the dog.

it's diluted or concentrated

in a diluted solution, you can add a lot more solute but in concentrated only a little more can be added