question: Why the weather changes, immune system become weak?
comment: It's actually more to do with the humidity / moisture in the air. Colds and flu are spread by coughs and sneezes (mucous). Warmer weather normally has wetter air. Wetter air: 1. makes it more likely for germy bits of mucous etc to stay in bigger clumps and fall to the ground faster (drier air makes them break up and spread further - they basically become mist) 2. might deform the virus cells' surfaces, as well, because of acidity Sources: [scientific article on influenza and humidity]( URL_0 ) [BBC article on why germs spread in winter]( URL_1 )
passages: Infectious disease often accompanies extreme weather events, such as floods, earthquakes and drought. These local epidemics occur due to loss of infrastructure, such as hospitals and sanitation services, but also because of changes in local ecology and environment. For example, malaria outbreaks have been strongly associated with the El Niño cycles of a number of countries (India and Venezuela, for example). El Niño can lead to drastic, though temporary, changes in the environment such as temperature fluctuations and flash floods. Because of global warming there has been a marked trend towards more variable and anomalous weather. This has led to an increase in the number and severity of extreme weather events. This trend towards more variability and fluctuation is perhaps more important, in terms of its impact on human health, than that of a gradual and long-term trend towards higher average temperature.
   With increasing weather extreme trends, vector and water-borne diseases, as well as allergies become more prevalent in these conditions. These infectious diseases and what accompanies them (mosquitoes, tics etc.) rely upon the environment to spread and survive. The reproduction and spread of these diseases are severely affected by weather fluctuations.
   state of Florida. As of 1990, about 200 cases of PAM had been reported worldwide; as of 2007, 132 cases had been reported in the U.S. PAM occurs throughout the world, including colder climates, such as the UK and Belgium. In 2007, PAM cases were also reported in Texas and Arizona. Water-borne diseases investigated by the Orange County Health Department, the Florida Department of Health and the CDC have also included Giardia, Cyclosporiasis and Cryptosporidiosis. Techniques for identifying Cyclosporiasis were first developed in central Florida. The Florida Department of Health in Orange County, the Florida Department of Health and the CDC advise swimmers and water sports enthusiasts to wear nose plugs when the ambient temperatures exceed 80 degrees when choosing to participate in freshwater activities. However, these have not been shown to prevent the disease. Avoiding fresh water during the hot season appears to be the safest practice. Naegleria fowlerii infection of young teenagers is best described as one of a number of very rare, "orphan diseases".
   Section::::Environment.
  
  This pathogen has a wide geographical distribution. Strains of the pathogen are present throughout various climates worldwide. Temperature can affect how symptoms appear on the host. Optimal temperature for growth of "C. acutatum" is 25 degrees Celsius. For instance, in weather with high humidity, orange colored spores appear on the hosts’ lesions. Specifically in strawberries, this disease appears to be more harmful in warm climates. " "Transference of disease occurs when conidia are spread by water, specifically rain or irrigation water. Another way of contamination is from infected equipment or wind. 
  
  Section::::Management.
  
  Section::::Management.:Cultural Control.
   Airborne transmission of disease depends on several physical variables endemic to the infectious particle. Environmental factors influence the efficacy of airborne disease transmission; the most evident environmental conditions are temperature and relative humidity. The sum of all the factors that influence temperature and humidity, either meteorological (outdoor) or human (indoor), as well as other circumstances influencing the spread of the droplets containing the infectious particles, as winds, or human behavior, sum up the factors influencing the transmission of airborne diseases.
   Arguably one of the worst effects that drought has directly on human health is the destruction of food supply. Farmers who depend on weather to water their crops lose tons of crops per year due to drought. Plant growth is severely stunted without adequate water, and plant resistance mechanisms to fungi and insects weaken like human immune systems. The expression of genes is altered by increased temperatures, which can also affect a plant's resistance mechanisms. One example is wheat, which has the ability to express genes that make it resistant to leaf and stem rusts, and to the Hessian fly; its resistance declines with increasing temperatures.
   Warming oceans and a changing climate are resulting in extreme weather patterns which have brought about an increase of infectious diseases—both new and re-emerging. These extreme weather patterns are creating extended rainy seasons in some areas, and extended periods of drought in others, as well as introducing new climates to different regions. These extended seasons are creating climates that are able to sustain vectors for longer periods of time, allowing them to multiply rapidly, and also creating climates that are allowing the introduction and survival of new vectors.
  
  Section::::Impact on disease.:Impact on infectious diseases.:Impact of warmer and wetter climates.
   Currently, pathogens take 10-16% of the global harvest and this level is likely to rise as plants are at an ever-increasing risk of exposure to pests and pathogens. Historically, cold temperatures at night and in the winter months would kill off insects, bacteria and fungi. The warmer, wetter winters are promoting fungal plant diseases like soybean rust to travel northward. Soybean rust is a vicious plant pathogen that can kill off entire fields in a matter of days, devastating farmers and costing billions in agricultural losses. Another example is the Mountain Pine Beetle epidemic in BC, Canada which killed millions of pine trees because the winters were not cold enough to slow or kill the growing beetle larvae. The increasing incidence of flooding and heavy rains also promotes the growth of various other plant pests and diseases. On the opposite end of the spectrum, drought conditions favour different kinds of pests like aphids, whiteflies and locusts.
   The mould is highly weather sensitive. During the time when the weather is cool, wet, or overcast the disease can evolve in a greenhouse or field. The disease spreads rapidly because of the pathogen. The rate of continental spread is based on the potential for high levels of inoculum and effective wind spores. When the weather is clear, dry, and hot the disease usually stops spreading and more than likely stops all together.
  
  Section::::Spreading the disease.
   Ultraviolet light (UV) is the light in sunlight and can inactivate viruses by causing cross-linking of the nucleotides in the viral genome. Many viruses in water are exterminated in the presence of sunlight. The combination of higher temperatures and more UV in the summer time corresponds to shorter viral survival in summer compared to winter. Double stranded DNA viruses like adenoviruses are more resistant to UV light inactivation than enteroviruses because they can use their host cell to repair the damage caused by the UV light.
   Warm temperatures, storms, adverse living conditions, poverty, and harmful land use policies all contribute to increased risk for leptospirosis. As global climate change continues to drive convergence of these factors, especially in tropical islands like Puerto Rico, local public health officials and their governments face a multitude of challenges. Leptospira bacteria can survive longer at higher temperatures, with more human cases observed during summer months. Increased rainfall and flooding associated with climate change opens up transmission pathways for leptospirosis and other zoonotic diseases, such as damaged sanitation and water treatment systems, flooded farms, and rodents or other animals seeking shelter and dry land.
   Communicable diseases are increased due to many pathogens and bacteria that are being transported by the water. In floods where there are many fatalities in the water there is a hygienic problem with the handling of bodies, due to the panic stricken mode that comes over a town in distress. There are many water contaminated diseases such as cholera, hepatitis A, hepatitis E and diarrheal diseases, to mention a few. There are certain diseases that are directly correlated with floods they include any dermatitis and any wound, nose, throat or ear infection. Gastrointestinal disease and diarrheal diseases are very common due to a lack of clean water during a flood. Most of clean water supplies are contaminated when flooding occurs. Hepatitis A and E are common because of the lack of sanitation in the water and in living quarters depending on where the flood is and how prepared the community is for a flood.
   Respiratory diseases are a common after the disaster has occurred. This depends on the amount of water damage and mold that grows after an incident. Vector borne diseases increase as well due to the increase in still water after the floods have settled. The diseases that are vector borne are malaria, dengue, West Nile, and yellow fever.
   The spread of disease is favored in cool, wet, and humid conditions in late fall or early spring when conidia are most abundant. Regions with irrigation are particularly vulnerable to disease, for conidia thrive whenever water is available. Studies have shown that there are positive correlations between the number of disease causing agents (conidia), and the number of hours that temperatures are between 10 and 15 degrees Celsius. These data also correlate to the duration of moisture and amount of time humidity conditions are above 90 percent. These conditions are all optimal for disease. Without humidity and wet conditions, disease does not occur.
   The rate of infection is higher when periods of frequent precipitation and warm weather coincide with flowering. Heavy dew or extended periods of misty weather are particularly favorable. Low temperatures at the beginning of the flowering period and dry conditions toward the end of it most likely reduce the infection potential.
   Subak (2003) proposes that a link between human behavior and precipitation could be another factor in Lyme disease incidence. In the northeastern United States when the summer weather is especially hot and dry, it may disincline people from outdoor activity. In fact, Subak (2003) found a link between dry conditions and a decreased Lyme disease incidence during late summer months in the northeast United States.
   Other diseases on the rise due to extreme weather include hantavirus, schistosomiasis, onchocerciasis (river blindness), and tuberculosis. It also causes the rise in hay fever, as when the weather gets warmer there is a rise in pollen levels in the air.
  
  Projected increases in temperature would make parts of southwest Asia uninhabitable, when temperature combined with high humidity reaches a wet-bulb temperature of 35 °C, the threshold for a fit human to survive in well-ventilated conditions.
   This trend towards more variability and fluctuation is perhaps more important, in terms of its impact on human health, than that of a gradual and long-term trend towards higher average temperature. Infectious disease often accompanies extreme weather events, such as floods, earthquakes and drought. These local epidemics occur due to loss of infrastructure, such as hospitals and sanitation services, but also because of changes in local ecology and environment.
  
  Section::::Health.:Diseases.
   For some diseases it is important to consider the disease occurrence over several growing seasons, especially if growing the crops in monoculture year after year or growing perennial plants. Such conditions can mean that the inoculum produced in one season can be carried over to the next leading to a build of inoculum over the years. In the tropics there are no clear-cut breaks between growing seasons as there are in temperate regions and this can lead to accumulation of inoculum.
   Section::::Epidemiology.
  
  "Didymella bryoniae" is common in the Southern U.S. and other subtropical or tropical locations . Most infections occur during rainy/wet seasons, in which the humid is greater than 90% and the temperature is roughly 20-24 °C . Humidity seems to be a larger factor than temperature when it comes to infection success . "D. bryoniae" can also be found in temperate regions, especially where winter squash and pumpkins are grown . This pathogen is also common in greenhouses where cucumbers are grown .
   High rainfall and warm temperatures are most favorable for this pathogen and lead to rapid disease development.
  
  During mid to late spring, infections may be most severe due to frequent rain showers. The optimal temperature that will allow for most successful growth of the pathogen and development of disease is around 25°C. The fungal pathogen favors 12 or more hours of leaf wetness for infection. New, young foliage has been found to be more susceptible to the pathogen when compared to mature, developed foliage.
  
  Section::::Management.
   Section::::Environment.
  
  "P. megakarya" is found in Central and Western Africa. During the cooler wetter times of the year, there is a spike in the incidents of black pod disease as when compared to the hotter more dry times of the year. The disease has a spike shortly after a rainfall.
   BULLET::::- Climate and living area. Rainfall (number of rainy days being more important than total precipitation), mean of sunshine daily hours, latitude, altitude are characteristic agents to take in account when assessing the possibility of spread of any airborne infection. Furthermore, some infrequent or exceptional extreme events also influence the dissemination of airborne diseases, as tropical storms, hurricanes, typhoons, or monsoons. Climate conditions determine temperature, winds and relative humidity in any territory, either all year around or at isolated moments (days or weeks). Those are the main factors affecting the spread, duration and infectiousness of droplets containing infectious particles. For instance, influenza virus, is spread easily in northern countries (north hemisphere), because of climate conditions which favour the infectiousness of the virus but on the other hand, in those countries, lots of bacterial infections cannot spread outdoor most of the year, keeping in a latent stage.
   Ticks, biting flies, and contact with other infected animals also causes the spread of rainscald. Once in the skin, the bacteria cause inflammation of the skin as well as the typical symptoms associated with rainscald.
  
  Section::::Symptoms.
   Temperature and moisture are the two most important environmental conditions for the development of "L. maculans" spores. A temperature of 5-20 degrees Celsius is the optimal temperature range for pseudothecia to mature. A wet humid environment increases the severity of the disease due to the dispersal of conidia by rain splash. As well as rain, hail storms also increase the severity of the disease.
  
  Section::::Management.
  
presuppositions: When weather changes, your immune system becomes weak. Weather changes cause immune system to weaken.
corrections: When it is less humid, viruses can spread more effectively. Humidity and moiusure allow viruses to spread more easily. Immune system doesn't weaken. 
raw_presuppositions: When weather changes, your immune system becomes weak. Weather changes cause immune system to weaken.
raw_corrections: When it is less humid, viruses can spread more effectively. Humidity and moiusure allow viruses to spread more easily. Immune system doesn't weaken. 