This pathology has also been seen in certain East-African tribes who eat foods (Matoke —a green banana) containing excess amounts of serotonin. Connection with direct serotonergic agonist drugs
Elevated prevalence of cardiac fibrosis and related valvopathies was found to be associated with use of a number of unrelated drugs following long-term statistical analysis once the drugs had been on the market for some time. The cause of this was unknown at the time, but eventually it was realised that all the implicated drugs acted as agonists at 5-HT2B receptors in the heart in addition to their intended sites of action elsewhere in the body.The precise mechanisms involved remain elusive however, as while the cardiotoxicity shows some dose–response relationship, it does not always develop, and consistent daily use over an extended period tends to be most strongly predictive of development of valvopathy.The drugs most classically associated with the condition are weight loss drugs such as fenfluramine and chlorphentermine, and antiparkinson drugs such as pergolide and cabergoline, which are prescribed for chronic use.The heart valve changes seen with moderate and intermittent use can result in permanent damage and life-threatening heart problems if use of the causative drug is increased or continued, however longitudinal studies of former patients suggest that the damage will heal over time to some extent at least.
A subclinical infection — sometimes called a preinfection or inapparent infection — is an infection that, being subclinical, is nearly or completely asymptomatic (no signs or symptoms). A subclinically infected person is thus a paucisymptomatic or asymptomatic carrier of a microbe, intestinal parasite, or virus that usually is a pathogen causing illness, at least in some individuals. Many pathogens spread by being silently carried in this way by some of their host population. Such infections occur both in humans and animals.An example of an asymptomatic infection is a  mild common cold that is not noticed by the infected individual. Since subclinical infections often occur without eventual overt sign, their existence is only identified  by microbiological culture or DNA techniques such as polymerase chain reaction. Infection transmission/signs
An individual may only develop signs of an infection after a period of subclinical infection, a duration that  is called the incubation period. This is the case, for example, for subclinical sexually transmitted diseases such as AIDS and genital warts. It is thought that individuals with such subclinical infections, and those that never develop overt illness, creates a reserve of individuals that can transmit an infectious agent to infect other individuals. Because such cases of infections do not come to clinical attention, health statistics can often fail to measure the true prevalence of an infection in a population, and this prevents the accurate modeling of its infectious transmission.