Question

The female mosquito needs your blood to grow her eggs. Please don’t feel singled out. She bites everyone. There is no truth to the myths that mosquitoes prefer women over men or blondes and redheads over those with darker hair. She does, however, play favorites. Type O blood seems to be the vintage of choice. Stinky feet emit a bacterium that woos famished females, as do perfumes. As a parting gift, she leaves behind an itchy bump (an allergic reaction to her saliva) and potentially something far worse: infection with one of several deadly diseases, including malaria, Zika, West Nile, dengue and yellow fever. Mosquitoes are our apex predator, the deadliest hunter of human beings on the planet. A swarming army of 100 trillion or more mosquitoes patrols nearly every inch of the globe, killing about 700,000 people annually. Researchers suggest that mosquitoes may have killed nearly half of the 108 billion humans who have ever lived across our 200,000-year or more existence. Flying solo, the mosquito does not directly harm anyone. It is the diseases she transmits that cause an endless barrage of death. Yet without her, these pathogens could not be vectored to humans. Without her, human history would be completely unrecognizable.The mosquito and her diseases have accompanied traders, travelers, soldiers and settlers (and their captive African slaves) around the world and have been far more lethal than any manufactured weapons or inventions. Malarious mosquitoes patrolling the Pontine Marshes facilitated both the rise and the fall of the Roman Empire. Initially shielding the Eternal City from the Visigoths, Huns and Vandals, they eventually pointed their proboscises inward on Rome itself. Mosquitoes defended the Holy Land during the Crusades by laying waste to armies of cross-adorned Christian soldiers. By infecting European soldiers with malaria and yellow fever, they reinforced numerous successful rebellions in the Americas during the late 18th and early 19th centuries, including the British surrender at Yorktown during the American Revolution.Mosquitoes also played a role in steering slave ships from Africa across the Atlantic, because plantation owners in the Americas believed that Africans withstood the onslaught of mosquito-borne disease better than indigenous slaves or European indentured servants. Malaria often produces a synchronized and cyclical pattern of symptoms: a cold stage of chills and shakes, followed by a hot stage marked by fevers, headaches and vomiting, and finally a sweating stage. After a period of respite, this progression repeats itself. For many, especially children under 5, malaria triggers organ failure, coma and death.Today, roughly four billion people are at risk from mosquito-borne diseases. As our ancestors can attest, our battle with the mosquito has always been a matter of life and death, and it’s beginning to look as though this confrontation is coming to a head.

Questions

1. Describe the disease using the epidemiologic triangle model.

2. Report the descriptive epidemiology of the disease for a recent significant epidemic or pandemic (in the United States or not).

Answer 1

1. An epidemiologic triangle is a tool that helps in understanding infectious diseases. In the case of malaria, this model of epidemiologic disease causation is made up of an external agent, Plasmodium falciparum; a susceptible host, humans; and a favorable environment with mosquitoes that allows the host and agent to be together. These three form the 3 vertices of the epidemiological triangle. In this triad, the disease is the result of the interaction between the external agent plasmodium and the susceptible host in an environment that is favorable for the transmission of the agent from a source to the host. The pathogens or agents are vectored to humans by female Anopheles species mosquito.

2. Descriptive epidemiology for, a recent significant epidemic, HIV:

HIV is a viral infection, where the virus is the causative agent, which infects the immune system. Thus the HIV infected person becomes more vulnerable to other forms of infection. As the immune system gets infected with this virus, the body cannot fight HIV on its own. HIV is transmitted through direct contact with an infected person’s body fluids, and it mostly spreads through shared needles, blood transfusion, or sexual contact.

Scientists say that HIV was originally carried by chimpanzees, the first hosts. As per this theory, humans who killed chimpanzees for meat got infected with a mutated virus form by getting in contact with the chimpanzee blood. This virus is transmitted when the body fluid gets in contact with damaged tissue or mucous membrane.

A number of socioeconomic and other factors are there that affect the transmission of HIV in a community. Groups with higher incidences of sexually transmitted diseases and a lower number of reporting, allow HIV to flourish. In places where access to care and treatment is limited by poverty, discrimination etc., individuals are discouraged from getting tested, thus becoming a favorable environment.