Chikungunya Virus in the Southeast

The virus is transmitted by the yellow fever mosquito, which also carries yellow fever and dengue fever. The virus can cause fever and joint pain that can be debilitating in severe cases. The virus cannot be transmitted between people, but only by mosquito bite. There is no vaccine against it. Chikungunya outbreaks have been reported in several Central American and Caribbean countries in the past two years. So far, all the reported cases in the U.S. have been by travelers to countries where the virus is established.

The virus can spread by a mosquito biting someone infected and then biting someone without the disease. The CDC is worried that the virus will spread to the United States from either infected mosquitoes from Caribbean countries or from infected individuals introducing the virus into the yellow fever mosquitoes already found in the United States, and possibly other mosquito species.

Symptoms develop within 3 to 7 days of infection. The fever usually lasts a few days to a week, but the joint pain may last more than a month. Anyone with a fever, headache, rash, and/or joint pain should go to a doctor.

The CDC gives guidelines to prevent mosquito bites and possible infection.

• Use air conditioning or window/door screens to keep mosquitoes outside. If you are not able to protect yourself from mosquitoes inside your home or hotel, sleep under a mosquito bed net.
• Help reduce the number of mosquitoes outside your home or hotel room by emptying standing water from containers such as flowerpots or buckets.
• When weather permits, wear long-sleeved shirts and long pants.
• Use insect repellents.
• Repellents containing DEET, picaridin, IR3535, and oil of lemon eucalyptus and para-menthane-diol products provide long lasting protection.
• If you use both sunscreen and insect repellent, apply the sunscreen first and then the repellent. 
• Do not spray repellent on the skin under your clothing.
• Treat clothing with permethrin or purchase permethrin-treated clothing.
• Always follow the label instructions when using insect repellent or sunscreen.

CDC Chikungunya virus
 AL.com First Alabama Virus Case

Yersinia Infections in Transfusions

  by  makelessnoise 

Yersinia enterocolitica is a human pathogen that affects the G.I. system. It causes fever, diarrhea, and abdominal pains, and can sometimes be mistaken for appendicitis and is usually spread by contact with fecal material. However, it is a very important infection in blood banking, as it is the leading cause of post-transfusion septic infections.

Y. enterocolitica is a common contaminant is stored blood. The bacteria has several adaptions that allow it to thrive under the conditions blood is stored. Yersinia species are siderophilic, meaning they like high-iron environments, as is in stored blood. Y. enterocolitica can survive and even reproduce in temperatures down to -2C, allowing them to grow at the refrigerated temperatures blood is stored. The bacteria use glucose and adenine, found in storage additives, for metabolism and growth, and have an optimal pH of 7.0 – 8.0, and blood is stored around 7.3. It has been shown calcium prevents growth of pathogenic Yersinia but only above 30C, so blood stored with a calcium chelated anticoagulant does not prevent infection.

Y. enterocolitica can cause an asymptomatic infection in the intestines that disseminates to the blood, which is how is eventually contaminates stored blood. Donors who are asymptomatic or who have bacterial counts low enough to not present symptoms are not routinely screened. The bacteria do not actively cause sepsis, but trigger a major generalized inflammatory response, thought to be the result of a cell wall component that strongly binds to and activates macrophages, who initiate a cytokine cascade throughout the body.

Serologic donor testing is expensive and infections caused by Y. enterocolitica is relatively rare. The simplest ways to prevent post-transfusion infections from the bacteria are not allowing donors the give blood if they do not feel well or have any signs of infection, not giving blood older than 3 weeks to susceptible recipients because the  bacteria take 3 to 4 weeks to reach dangerous levels in refrigerated blood, and using pre-storage leukocyte-reducing techniques because the bacteria have a strong affinity for WBCs.

http://www.ncbi.nlm.nih.gov/pubmed/21865196

Sous-vide Cooking and Bacteria

I have a confession: I love to cook. It's a combination of art and science, and you can eat the final product! My favorite aspect of cooking is food science and learning the processes that take raw ingredients and turn them into food, and I read a lot about modern and next gen cooking techniques. That's how I learned about and started using sous-vide.

  by  AustinMatherne 

Sous-vide is a cooking method like baking, broiling, or grilling. Food is placed into a vaccum-sealed bag and usually submersed in a water bath. The water is kept at a precise temperature using some type of heater/thermostat combination and the food is cooked by heat diffusion through the bag. The food cooked this way is not soggy, the flavors are sealed with the food, and extremely specific temperatures can be used. Most sous-vide is done with meat. Steaks can be cooked to a perfect medium-rare just by setting the temperature to the correct degree. And because the water, and therefore the food, never exceeds that temperature and no moisture is lost, food can be left in it for days without overcooking. The problem is most sous-vide cooking takes place between 120F to 150F; in the bacterial danger zone.

The theory behind preparing food safely is bacteria don't have a thermometer that kills them only if a certain temperature is reached. There are charts, graphs, and computer models that predict the death rate of certain food-borne pathogens, and the rate is a curve. Cooking chicken to 165F kills salmonella in a few seconds, but it take several minutes to completely kill at 150F. So theoretically, as long as you let food sit in the water bath long enough, it will pasteurize it and be as safe as conventional cooking, while being juicer and more tender.

However, most models for recommended cooking times do extend into the low temperatures that sous-vide uses. Many publications exist, but few actually link scientific or regulatory reports for the cooking times. Here is a page from a popular sous-vide immersion circulator company that lists times and temperatures, but the only source is a link to the FDA homepage. Most cooking times are based on the old models for high temperature, so the temperatures are not approved by food agencies. But the Institute of Food Research in the UK and the USDA/FDA have both begun programs to update the current models to include low temperature cooking.

I personally don't have a problem with sous-vide and have made several meals at home without any problems using the times provided from other chefs, as have many other people. I will continue to use sous-vide as an alternative cooking method and use safe food-handling practices when cooking to keep the risk for contamination low.

Douglas Baldwin: A Practical Guide to Sous Vide Cooking

Institute of Food Research Bacterial Growth Model Study pdf

Glowing Burn Dressings Detect Infections

Burns are some of the most difficult wounds to treat. Large open sores are easy for bacteria to colonize, and most serious burns require hospitalization, which can lead to exposure to infectious pathogens. The pathophysiologic response to a burn, as well as its involvement with skin that is colonized by opportunistic pathogens, are the major reasons for infections. A burn compromises the innate protection of the skin, decreases T-cell activity by decreasing the number of helper cells, decreases the levels of inflammatory cytokines and complements, and decreases the bactericidal activity of neutrophils. Common bacteria that infect burn wounds include Staphylococcus aureus, Pseudomonas aeruginosa,  Klebsiella pneumoniae, and Acinetobacter  baumannii.  

Currently, if an infection is suspected, the wound dressing is removed so a swab or scraping can be obtained. This exposes the wound, increases healing time and the likeliness a scar will develop. Testing of the sample can take several days to culture and identify the bacteria. The University of Bath's biochemistry department has developed a wound dressing patch that fluoresces in the presence of infectious bacteria. Most bacteria causing infections release toxins. These toxins break down nanocapsules which are filled with a fluorescent compound and bacteriophages. The fluorescent chemical glows under UV light, alerting doctors to an infection without removing the dressing, and can even detect toxins at concentrations below that which the body starts reacting, allowing doctors to start treatment before the bacteria cause an actual infection. The bacteriophages are viruses that attack and kill bacteria. They can help prevent and stop infections, even by those caused by microbes like MSRA that are resistant to antibiotics. The patches work well in the laboratory, but it will be some time before human trials begin.


University of Bath Research

Burn Wound Pathophysiology