### Epidemiology: What is Bias, Chance, and Confounders in Epidemiology?

Amidst the confusion created by confounders and other factors not obviously causing the disease, epidemiologist use statistics and derive conclusions using p-value or probability which measure chance!

### Epidemiological Study Designs: An Introduction to Epidemiological Studies

Epidemiology definition is not just a definition but a philosophy

### Vectors of Medical Importance

#vectors By Dr Khushboo Hadiya PSM

Vector-borne diseases are a major public health concern, affecting around half of the world’s population. Vectors are living organisms that can transmit infectious diseases between humans or from animals to humans.

Many of these vectors are bloodsucking insects, which ingest disease-producing microorganisms during a blood meal from an infected host (human or animal) and later inject it into a new host during their subsequent blood meal.

Mosquitoes are the best-known disease vector. Others include ticks, flies, sandflies, fleas, triatomine bugs, and some freshwater aquatic snails.

### Probability Bay’s theorem: Surprisingly Easy To Understand

Bayes’ theorem is a fundamental concept in probability theory that describes the relationship between the probability of an event occurring (the prior probability) and the probability of that event occurring given certain evidence (the posterior probability). The theorem is named after Thomas Bayes, an 18th-century statistician and theologian who first published the theorem in his 1763 essay “An Essay Towards Solving a Problem in the Doctrine of Chances.”

The theorem is expressed mathematically as:

P(A|B) = P(B|A) * P(A) / P(B)

Where:

• P(A|B) is the probability of event A occurring given that event B has occurred (the posterior probability)
• P(B|A) is the probability of event B occurring given that event A has occurred (the likelihood)
• P(A) is the probability of event A occurring (the prior probability)
• P(B) is the probability of event B occurring (the marginal likelihood or the normalizing constant)

The theorem is used to update the probability of an event occurring based on new information or evidence. It can be used in a wide range of applications, including decision-making, machine learning, natural language processing, and medical diagnosis.

It is important to note that Bayes’ theorem is based on the assumption of conditional independence, which means that the probability of an event occurring is not affected by the occurrence of other events.

### Mosquito-Borne Diseases, Vector Born Diseases, Insecticides -I

A vector-borne disease is a type of illness that is transmitted to humans (or other animals) by an intermediate host, known as a vector. Vectors are organisms that carry pathogens (disease-causing agents) and transmit them to other living creatures.

## Mosquito-Borne diseases (Mosquito-Transmitted Diseases)

Mosquitoes are vectors (organisms that transmit diseases) for a number of diseases. Some of the most common mosquito-borne diseases include:

• Malaria: Malaria is a tropical disease caused by parasites that are transmitted to humans through the bites of infected mosquitoes. It can cause fever, chills, and flu-like symptoms, and can be severe or even fatal if left untreated.
• West Nile virus: West Nile virus is a viral illness that is transmitted to humans through the bites of infected mosquitoes. It can cause fever, headache, muscle weakness, and sometimes a rash or swollen lymph nodes. In rare cases, it can lead to severe neurological symptoms such as encephalitis or meningitis.
• Zika virus: Zika virus is a viral illness that is transmitted to humans through the bites of infected mosquitoes. It can cause fever, rash, joint pain, and conjunctivitis (red eyes). Zika virus infection during pregnancy can cause severe birth defects in infants, including microcephaly (a small head and brain).
• Chikungunya virus: Chikungunya virus is a viral illness that is transmitted to humans through the bites of infected mosquitoes. It can cause fever, joint pain, and rash.
• Dengue fever: Dengue fever is a viral illness that is transmitted to humans through the bites of infected mosquitoes. It can cause fever, headache, muscle and joint pain, and a rash. In severe cases, it can lead to dengue hemorrhagic fever, which can be fatal.

To prevent mosquito-borne diseases, it is important to take precautions to avoid mosquito bites, such as using insect repellent, wearing long sleeves and pants, and using mosquito netting. In some areas, insecticides may be used to control the mosquito population. Vaccines are also available for some mosquito-borne diseases, such as yellow fever and Japanese encephalitis.

## Vector Born Diseases

A vector-borne disease is a type of illness that is transmitted to humans (or other animals) by an intermediate host, known as a vector. Vectors are organisms that carry pathogens (disease-causing agents) and transmit them to other living creatures.

Examples of vectors include:

• Mosquitoes: Mosquitoes are the most common vectors of diseases. They transmit diseases such as malaria, West Nile virus, Zika virus, chikungunya virus, and dengue fever.
• Ticks: Ticks are vectors of diseases such as Lyme disease, Rocky Mountain spotted fever, and tularemia.
• Sand flies: Sand flies are vectors of diseases such as leishmaniasis.
• Lice: Lice are vectors of diseases such as epidemic typhus and trench fever.
• Fleas: Fleas are vectors of diseases such as the plague.

## Control of Mosquitos Using Insecticides

Insecticides are chemical compounds that are used to kill or control the population of insects. Mosquitoes are a common target of insecticides, as they are vectors (organisms that transmit diseases) for a number of diseases, including malaria, West Nile virus, Zika virus, chikungunya virus, and dengue fever.

There are several different types of insecticides that can be used to control mosquitoes, including:

## Pyrethroids:

• Pyrethroids are synthetic chemicals that are similar to naturally occurring compounds called pyrethrins, which are found in certain plants. Pyrethroids are effective against a wide range of insects, including mosquitoes, and are often used in mosquito control.

## Organophosphates:

• Organophosphates: Organophosphates are a type of insecticide that works by disrupting the nervous system of insects. They are effective against a wide range of insects, including mosquitoes, but can also be toxic to humans and other animals if not used properly.

## Carbamates:

• Carbamates: Carbamates are a type of insecticide that works by inhibiting an enzyme that is necessary for the proper functioning of the nervous system in insects. They are effective against a wide range of insects, including mosquitoes, but can also be toxic to humans and other animals if not used properly.

Insecticides can be applied to surfaces or released into the air to control mosquito populations. They can also be applied to clothing or skin as a personal insect repellent. It is important to use insecticides according to the manufacturer’s instructions and to follow all safety precautions to avoid exposure to toxic chemicals.

## What Is Integrated Vector Control Measure?

Integrated vector control is a public health approach that combines a range of strategies to control vector-borne diseases. Vectors are organisms that transmit diseases, such as mosquitoes, ticks, and sandflies. Integrated vector control involves using a combination of approaches to reduce the risk of vector-borne diseases, including:

1. Chemical control: This involves the use of insecticides to kill or control vector populations.
2. Physical control: This involves the use of physical barriers, such as screens, to prevent vectors from entering homes and other buildings. It also involves eliminating standing water (where mosquitoes lay their eggs) and improving sanitation to reduce the breeding sites of vectors.
3. Biological control: This involves the use of natural predators or parasites to reduce vector populations.
4. Educational and behavioral interventions: This involves educating the public about how to prevent vector-borne diseases, such as using insect repellent and wearing protective clothing.
5. Engineering Measures: Mosquitoes lay their eggs in standing water, so eliminating sources of standing water can help reduce the mosquito population. This can be done by emptying containers that hold water (such as buckets, tires, and bird baths), repairing leaks, and properly maintaining pools and other water sources. Proper Storage and Disposal of Solid waste is also very important.

Integrated vector control is a multifaceted approach that aims to reduce the risk of vector-borne diseases in a sustainable and cost-effective manner. It is important to use an integrated approach, as no single strategy is sufficient on its own to control vector-borne diseases.

Source WHO

## 20 most important things about mosquito-born diseases

1. Mosquitoes are small insects that can transmit diseases such as malaria, dengue fever, and Zika virus.
2. Mosquitoes are most active during dusk and dawn and are attracted to the carbon dioxide, lactic acid, and other chemicals produced by humans and animals.
3. Female mosquitoes require blood to produce eggs, and they can transmit diseases during the blood-feeding process.
4. Mosquitoes breed in standing water, such as in pools, ponds, and ditches, and can lay hundreds of eggs at a time.
5. Malaria is the most well-known disease transmitted by mosquitoes and is caused by the Plasmodium parasite. It can lead to fever, chills, and flu-like symptoms, and can be fatal if left untreated.
6. Dengue fever is also transmitted by mosquitoes and is caused by the dengue virus. It can cause severe fever, headache, muscle and joint pain, and a rash.
7. Zika virus is transmitted by mosquitoes and can cause fever, rash, joint pain, and conjunctivitis. It is particularly dangerous for pregnant women as it can cause birth defects in the baby.
8. Chikungunya is another mosquito-borne disease caused by the chikungunya virus. It can cause fever, joint pain, and rash.
9. West Nile virus is transmitted by mosquitoes and can cause fever, headache, and muscle weakness. It can also lead to more severe symptoms such as encephalitis and meningitis.
10. Using mosquito repellent, wearing protective clothing, and staying indoors during peak mosquito hours can help prevent mosquito bites.
11. Eliminating standing water and using screens on windows and doors can also help reduce the mosquito population.
12. Insecticide-treated bed nets and indoor residual sprays can help control mosquitoes and prevent the transmission of disease.
13. Some species of mosquitoes are more likely to transmit certain diseases than others. For example, Anopheles mosquitoes are the primary vectors of malaria.
14. Climate change can affect the distribution and population of mosquitoes, potentially increasing the spread of disease.
15. Mosquitoes have developed resistance to certain insecticides, making it more difficult to control their populations.
16. The World Health Organization (WHO) recommends integrated vector management (IVM) as the most effective approach to controlling mosquitoes and preventing the spread of disease.
17. IVM involves using a combination of methods such as source reduction, biological control, and use of pesticides.
18. Vaccines are available for some mosquito-borne diseases, such as yellow fever, but not for others like Malaria, dengue, zika and chikungunya.
19. Mosquito-borne diseases disproportionately affect people living in low-income countries.
20. Research and development of new tools and strategies, such as genetically modified mosquitoes and disease-blocking vaccines, is ongoing to help control mosquitoes and prevent the spread of disease.