Drug makers and top scientists rake in enormous sums of money and the media boosts its audience ratings and circulations with sensationalized reporting the coverage of the "New York Times" and "Der Spiegel" are specifically analyzed. The enlightenment about the real causes and true necessities for prevention and cure of illnesses is falling by the wayside.
Apple Books Preview. Publisher Description. C: Xenopsylla cheopis the rat flea , one of the vectors of Yersinia pestis , which transmits the infecting bacteria from rats to human beings. D: Bifurcated needle used for smallpox vaccination during the last decades of smallpox eradication.
E: Cholera bed used to rehydrate patients with severe diarrhea; the drain in the middle is used to facilitate drainage of the copious diarrheal fluid. F: Cone barrier used to prevent rats from invading or leaving ships through the mooring ropes of the ship. Panel A from Wikipedia. Intriguingly, and according to databases managed by both Johns Hopkins University 7 and the European Centre for Disease Prevention and Control, 8 plots of the daily global numbers of COVIDinfected persons during the second trimester of reveal an undulating and ascending pattern that is difficult to explain.
However, they also show a progressive and steady decrease in mortality for that same period. The cumulative number and type of mutations detected during the first 6 months of do not explain the reduced severity of SARS-CoV Relatively few pandemics were caused by Gram-negative bacteria.
Yellow fever epidemics occur mainly in Africa and South America. The disease is transmitted by several species of mosquitoes, mainly by Aedes aegypti. The disease life cycle has two possible scenarios: 1 the sylvatic cycle, where the hosts are various types of animals, primarily monkeys; and 2 the urban cycle, where the reservoir is human beings. Outbreaks occur mainly during the rainy season. Water accumulation, on land or in various objects, facilitates development of vector mosquitos.
Other viruses transmitted by Aedes aegypti include dengue virus, Zika virus, and chikungunya virus. For close to half a century, several Ebola virus outbreaks have occurred in Western and Central Africa. The long-term reservoir of this virus is a species of bats. Due to massive deforestation, there have been episodes of viral spillover to humans and animals, including gorillas and chimpanzees. Subsequently, human-to-human transmission occurred as the result of close contact with patients or bodies at burial ceremonies, and some convalescing patients continued to transmit the virus for some time after recovery.
Due to the high contagiousness of Ebola, many health care workers were also infected. Currently, there is an effective vaccine to prevent Ebola Table 5 as well as a drug composed of three types of antibodies Table 6. During the twentieth century, there were four major pandemics: H1N1 caused the influenza pandemic; the pandemics of , , and were all descendants of the virus. The last of these pandemic influenza viruses incorporated genes by reassortment. In general, annual seasonal influenza in post-pandemic years is caused by variants of the corresponding virus from the prior pandemics.
Influenza viruses involved in seasonal flu accumulate antigenic changes in a progressive fashion resulting in annual seasonal epidemics.
An accepted parameter for the impact of annual influenza activity is the excess number of deaths. Epidemics and pandemics have had a very strong impact on human history. Diseases like smallpox, measles, and plague decimated entire populations in several regions of Europe, the Middle East, and Asia. At the end of the fifteenth century, the European conquistadores of the Americas brought diseases with them that were unknown to the native population.
Due to the local lack of immunity to these newly imported viruses, smallpox and measles spread rapidly, causing fear and frustration among the natives due to the lack of natural resistance and a very high mortality rate; local communities were decimated and sometimes entire settlements were wiped out. This tragedy facilitated the conquest of the land and the massive conversion of Indian tribes to Christianity across the Americas. Beginning in the last decade of the twentieth century, the AIDS pandemic intensified its spread on all continents, inflicting the greatest damage in Africa at the social, economic, and political levels.
Some of the manifestations of this megacatastrophe were the significant shortening of life expectancy, massive destruction of family units, and orphanhood. In addition, the profound immune suppression caused by HIV led to a rampant increase in the incidence and prevalence of tuberculosis and other infectious diseases.
Combined, these factors had a disastrous effect on the political structure of most African countries. Across history, pandemics have differentially infiltrated battling armies and in this way tipped the outcome of battles and war.
During the last decades and as a valuable complement to the written documentation on ancient bacterial pandemics, paleomicrobiological studies relating primarily to the plague Yersinia pestis have contributed greatly to the reshaping of our understanding of its epidemiology. There was much confusion and controversy regarding the epidemiology of plague in the multiple pandemics that occurred several centuries ago, until the studies of French investigators, Drancourt and Raoult and colleagues, which revolutionized several contentious concepts established by other investigators.
Additional epidemics investigated by the same scientists were found to be caused by Bartonella quintana alone or combined with Rickettsia prowazekii. With regard to smallpox, several well preserved mummies have been found in Egypt and other countries. Some mummies, such as that of the Egyptian pharaoh, Ramses V, provided dermal evidence that they had terminally suffered from smallpox.
However, genomic evidence for the actual virus has been found only rarely in mummies. This can be explained by the poor long-term preservation of viruses. Other diseases documented by paleomicrobiological methodologies include tuberculosis, leprosy, and multiple parasitic infections. For example, there may be a predisposition to COVID among humans with blood group A as opposed to other blood groups.
For example, a study of disease importation to continents, countries, or regions has surprisingly uncovered several shuffled patterns in the genomic data. When considering importation of the first COVID cases to the Western United States, the initial investigation based on contact tracing indicated that those cases were epidemiologically unrelated. However, after sequencing multiple virus isolates, the researchers concluded that they were not only closely related, but probably also began with one patient of origin.
A: Sequencing of representative isolates to create a phylogenetic tree of a coronavirus. B: Tracing a pandemic pathway. Specific viral isolates are sequenced to detect mutation and thereby reconstruct the chain of transmission. In panel B , each circle represents a coronavirus isolated from a patient. Different colors indicate a virus mutation. A series of questions must be answered when attempting to determine the primary source of a pandemic virus like SARS-CoV As it is a coronavirus, the most probable source is a virus that originated in bats.
If these sequences are identical, then it can be assumed that the primary source is a bat. In this scenario, especially if the laboratory is located in the proximity of the epidemic epicenter, a laboratory origin of the pandemic virus would be a strong alternative. Additional tests such as antibody testing of the personnel working in the suspected laboratory should provide further assistance in elucidating the true origin and pathway of the virus.
Other possible trajectories should also be investigated. For example, if early infections occurred in persons who had close contact to bats or other animals, such as animals raised on farms or held and sacrificed at wet markets, this would clearly point to a specific zoonotic link.
Another possibility is that the new virus was engineered for investigational purposes or with malicious criminal intentions. By looking at the structural details of the virus, molecular biologists have ruled out and published the arguments against this last-mentioned possibility. The COVID pandemic exemplifies the difficulties encountered when attempting to quantify the important numerical parameters of the disease. First of all, when trying to count the number of infected cases, this parameter is significantly underestimated, primarily because the proportion of people who are asymptomatic or suffering from mild disease are not yet known.
In this case, it is not easy to draw a line to those who should be considered a contact. In addition to underdetection of mainly asymptomatic patients, some deaths due to COVID complications passed under the radar since the patients had not been tested for the virus. Currently, there are many ongoing seroprevalence studies of anti-SARS-CoV-2 antibodies; however, the picture remains incomplete regarding the significance of these findings as markers of previous infections.
In , a cholera outbreak erupted in the densely populated neighborhood of Soho, London. John Snow, a physician who lived in the vicinity, mapped the houses of the many affected persons with cholera. He discovered a water pump in the center of the mapped area that had been used by all infected persons for obtaining drinking water.
On his advice, municipal authorities removed the pump handle, resulting in an immediate end to the epidemic, with no further cases. It was subsequently learned that human excrement pits had drained into and contaminated the water supply. In the s a major epidemic of cholera occurred in Peru.
Vibrio cholera contaminated the ballast water in ships that had arrived from India. Massive contamination of large quantities of live fish occurred when the ballast water was discharged into the sea near the shore. Fish were subsequently caught from this area, and thousands of Peruvians developed cholera after consuming raw fish ceviche , a popular traditional food.
The epidemic was terminated abruptly when the health authorities recommended to discard the head and branchia gills when preparing the fish for consumption. Following the spread of the COVID pandemic, the health authorities of most countries imposed a lockdown with various intervals of delay from the first detected case s so as to contain the local spread of the virus. Subsequently, they also imposed the use of respiratory masks to reduce airborne transmission by infected persons and to prevent contagion among the uninfected population.
Data from several countries have shown that the earlier and more stringent the lockdown was applied, the better the efforts in containing the pandemic. Table 5 lists the current availability of approved vaccines for pandemic diseases. Paradoxically, some of the newer diseases such as AIDS and those caused by coronaviruses still lack an approved effective vaccine.
Essentially, six groups of vaccines are being explored, three of which first require the isolation of viral particles. These virions are either: 1 weakened attenuated ; 2 killed by hot or chemical substances inactivated ; or 3 fragmented viruses followed by isolation of small pieces of the virus subunits.
Clinical trials are performed in three phases, each one having an increasing number of volunteers. Phase I 10— volunteers examines safety and immunogenicity. Phase III more than 10, volunteers primarily examines infection prevention following exposure. If all three phases are successful, then the vaccine undergoes regulatory approval and subsequent mass production under strict quality control. The main problem with the need to develop a vaccine against a new pandemic microbe is that the process is lengthy and mined with multiple obstacles.
If a proposed vaccine causes serious side effects or alternatively is not sufficiently immunogenic, the development process should be restarted from the beginning. In some cases, when a clinical evaluation of a vaccine reaches Phase III, the number of newly infected cases drops rapidly, making it difficult to test the actual efficacy of the vaccine in preventing infection.
In the quest for a COVID vaccine, there have been a few initiatives to recruit volunteers who would be challenged with the virus after being immunized. However, for this scheme to work, it is essential to have a very efficacious drug available for treating the infection, should the vaccine fail.
In general, with regard to the efficacy of antiviral treatments, viral infections can be divided into three groups: 1 infections lacking an effective antiviral therapy e. SARS, yellow fever, measles ; 2 infections in which antivirals do not cure the infection, but which do produce varying degrees of clinical improvement e. Ebola, hepatitis C. Table 6 provides an overview of the treatments used for different pandemic diseases. Despite an increase in antibiotic resistance, there remain multiple choices for treatment of bacterial pandemics.
For example, the main pillar of medical treatment for cholera is the emergency replacement of large amounts of fluid lost as a result of diarrhea and vomiting, with antibiotics playing a secondary role in its treatment.
The overwhelming death toll from COVID has sparked a myriad of projects to identify drugs that can be repurposed on a fast track to for special treatment of patients with severe disease. The administration of convalescent plasma from recovering patients with COVID is now being examined at different sites, including new clinical trials, but conclusions regarding this therapy are still pending.
The economic impact of past pandemics is hard to examine due to the lack of robust data. The harshest economic impact generally occurred in varying degrees in wealthier countries. One of the most important parameters for quantifying economic damage is the gross domestic product forecast, although different countries use other economic metrics.
According to the majority of prognoses, the damage was expected to be greatest during the second quarter of Quantification of financial activities in selected populations may add important data to more accurate evaluation of the world economy as a result of the COVID pandemic.
For example, listing the purpose of out-of-home visits residential, parks, workplace, grocery stores, pharmacy may contribute to a composite financial evaluation of representative family units.
Despite the rapid and advanced progress in many medical disciplines since the end of the nineteenth century, the COVID pandemic has sadly demonstrated vast limitations worldwide in successfully coping with it. There is no doubt that the unexpected and yet fully unknown behavior of SARS-CoV-2 has strongly contributed to its pandemic status.
For example, the high proportion of infected but totally asymptomatic persons has made containment challenging, to say the least.
Selected examples from prior pandemics should illuminate our vision for the future. Smallpox went from being a totally empiric vaccine to global eradication of the disease. However, AIDS, which is caused by a zoonotic retrovirus that translates its RNA to DNA and enters the human genome, presents an almost impossible challenge in approaching a total cure for the disease, although combinations of antivirals are able to halt or reverse the progression of the disease.
This retrospective analysis and comparison of COVID with prior pandemic diseases can contribute to the improvement of a rationale and scientific approach to future epidemics or pandemics. The most important take-away point should be an understanding of the high degree of preparedness that is needed, including various protocols for social distancing that are adapted to the different transmission modalities of the involved microbes.
Viruses are like hijackers. They invade living, normal cells and use those cells to multiply and produce other viruses like themselves. This can kill, damage, or change the cells and make you sick. Different viruses attack certain cells in your body such as your liver, respiratory system, or blood. When you get a virus, you may not always get sick from it.
Your immune system may be able to fight it off. For most viral infections, treatments can only help with symptoms while you wait for your immune system to fight off the virus. Antibiotics do not work for viral infections. There are antiviral medicines to treat some viral infections.
Vaccines can help prevent you from getting many viral diseases.
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