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Conditions that affect the bone marrow can also lead to thrombocytopenia. It may be necessary to examine bone marrow smears and sections to diagnose the primary condition that is causing the decrease in circulating platelets. In leukemia, the platelet count is diminished as a result of displacement in the bone marrow of normal hematopoietic cells (including megakaryocytes and their precursor cells) by leukemic cells. If megakaryocytes are reduced in the bone marrow, the number of circulating platelets will be reduced. Chemotherapy can lead to transient thrombocytopenia since it interferes with the cell cycle of normal as well as tumor cells. In patients with aplastic anemia, where the stem cells are not functioning properly, thrombocytopenia occurs as the bone marrow becomes more and more hypoproliferative. Pancytopenia is often seen with megaloblastic anemias that are caused by folic acid or vitamin B12 deficiency. Thrombopoiesis (as well as erythropoiesis and granulopoiesis) is ineffective. The bone marrow contains a normal, or even increased number of megakaryocytes, but the number of platelets entering the peripheral circulation is decreased.

Ependymal cells (see arrow), are part of the lining of the brain and ventricles. They produce cerebrospinal fluid (CSF) and are involved in circulating the CSF over the brain, ventricles and the spinal cord. These cells are not a common finding in CSF cytospins but may be present in cases of hydrocephalus or chronic ventricular infection. They usually appear as very large multinucleated clumps.In the image on the right, notice how large this clump is in comparison to the red blood cells in the background.

Orthochromic normoblasts are the last nucleated stage of erythroid maturation. In this stage, the nuclei of the cells completely shrink to a pyknotic remnant. The cytoplasm color approaches the color of a peripheral RBC as it becomes fully hemoglobinized. This is the stage that is most commonly seen when NRBCs are found in the peripheral blood. In the top image on the right there are many orthochromic normoblasts scattered across this section of bone marrow. Note the pyknotic-appearing nuclei which make them easy to spot, even at lower magnification. It is also evident that the cytoplasm is well hemoglobinized and the color is just slightly more blue than the non-nucleated red bloods cells present.In the higher magnification (second image), notice the orthochromic normoblast (blue arrow) to the right of the basophilic normoblasts. The color of the cytoplasm of the orthochromic normoblast is almost identical to the background RBCs. Notice how condensed the nucleus has become as well. You can actually observe the nucleus in the early stages of extrusion/elimination from the cell. Once the nucleus has been extruded, the slight blue color, also known as polychromasia, will begin to fade and the now non-nucleated RBC will be indistinguishable from any other circulating RBC.

Descriptions of cardiac biomarkers and their use require knowledge of several terms. These terms and their definitions follow.Acute Coronary Syndrome (ACS) Includes all the ischemic events that can occur in the heart. These events range from angina (where there is no cell death or reversible cell injury) to an AMI with large areas of cell necrosis. A continuum of events that are involved in ACS is illustrated on the page that follows this glossary of terms.Acute Myocardial Infarction (AMI) Commonly referred to as a heart attack. A sudden loss of circulating blood and oxygen that causes necrosis of myocardial tissue. It is most often caused by the narrowing of coronary arteries by atherosclerosis, a thrombus, or dislodged plaque material.Angina Chest pain caused by inadequate supply of oxygen to heart myocardium. It is synonymous with angina pectoris, pectoris meaning chest.Congestive Heart Failure (CHF) Usually, a left ventricular dysfunction resulting from aging, hypertension, atherosclerosis or muscle damage from an AMI or repeated AMIs. In CHF, the heart is not able to effectively pump blood through its chambers and to the body. Fluid accumulates in the lungs and tissues causing edema because less blood leaves through the arteries than what entered the heart from the veins. Electrocardiogram (ECG or EKG) The tracings of the electrical current that passes through the myocardium. The heart contractions are stimulated by this current. In areas of myocyte necrosis, the current does not pass and the tracings display abnormal patterns.Infarction An area of tissue death that occurs due to lack of oxygen. Clogging of an artery will cause dead muscle tissue or infarction.IschemiaAn inadequate blood supply that decreases availability of oxygen. Atherosclerosis is the main cause of myocardial ischemia.

A reactive pia arachnoid mesothelial cell as noted by the darker cytoplasm is present in this field. Reactive cells are a common finding in cytospin smears from spinal fluid samples and are sometimes difficult to distinguish from tumor cells. Mesothelial cells are usually interspersed among the other cells, rather than appearing in clumps. They have a single distinct nuclei that may be eccentric. The macrophages (histiocytes) are seen next to the mesothelial cell. Macrophages are distinguished from circulating monocytes by the irregular appearing cytoplasm. Bacteria, red cells or other debris can often be seen in the cytoplasm of macrophages.

As the name implies, coagulation inhibitors (also called circulating anticoagulants) interfere with normal blood coagulation. Coagulation inhibitors may be congenital or acquired (developing in patients during the course of a disease) and are almost always immunoglobulins, either IgG or IgM. There are two types of inhibitors: those directed toward a coagulation factor (or multiple factors) and the lupus anticoagulant. Lupus anticoagulant is one of the more commonly encountered coagulation inhibitors. It is also known as antiphospholipid antibody because it is directed toward phospholipids. Lupus anticoagulant is usually an IgG antibody. It differs from factor-specific inhibitors in that lupus anticoagulant causes thrombosis and abnormal clotting while factor-specific inhibitors cause serious bleeding.

Atherosclerosis. U.S. Department of Health & Human Services National Institutes of Health. Available at http://www.nhlbi.nih.gov/health/dci/Diseases/Atherosclerosis/Atherosclerosis_WhatIs.html Accessed March 25, 2013.Daniels LB, Barrett-Connor E, Sarno M, Laughlin GA,Bettencourt R, Wolfert RL. Lipoprotein-associated phospholipase A2 (Lp-PLA2) independently predicts incident coronary heart disease (CHD) in an apparently healthy older population: The Rancho Bernardo study. J Am Coll Cardiol. 2008;51:913-919.Executive Summary of the third report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA. 2001; 285:2486-2497. Frostegard, J, Wu R, Lemne C, Thulin T, Witztum JL and de Faire U. Circulating oxidized low-density lipoprotein is increased in hypertension, Clin Sci 2003; 105, 615.Garza CA, Montoir VM, McConnell JP, et al. Association between lipoprotein-associated phospholipase A2 and cardiovascular disease: a systematic review. Mayo Clin Proc. 2007;82(2):159-165.Interpretive Handbook, (MC0440rev0407) Mayo Clinic, RochesterMN;2007. Maksimowicz-McKinnon K, Bhatt DL, Calabrese LH: Recent advances in vascular inflammation: C-reactive protein and other inflammatory biomarkers. Curr Opin Rheumatol. 2004;16:18-24.Mora S, Szklo M, Otvos JD, et al. LDL particle subclasses, LDL particle size, and carotid atherosclerosis in the multi-ethnic study of atherosclerosis. Atherosclerosis. 2007;192:211-217.NACB Laboratory Medicine Practice Guidelines. Emerging biomarkers of cardiovascular disease and stroke. NationalAcademy of Clinical Biochemistry Laboratory Medicine Practice Guidelines. 2006.PLACtest animation, diaDexus. http://www.plactest.com/laboratorians/action.php Accessed March 25, 2013.Rifai N, Warnick GR. Lipids, lipoproteins, apolipoproteins, and other cardiovascular risk factors. In: BurtisCA, Ashwood ER. BrunsDE. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 4th ed. St. Louis, MO: Elsevier Saunders: 2006; chap. 26.Ridker PM, Rifai N, Rose L, et al. Comparison of C-reactive protein and low-density lipoprotein cholesterol levels in the prediction of first cardiovascular events. N Engl J Med. 2002;347:1557-1565.Sniderman AD. Differential response of cholesterol and particle measures of atherogenic lipoproteins to LDL-lowering therapy: Implications for clinical practice. J Clin Lipidol 2008;2:36-42.Tsimikas, S, Brilakis ES, Miller ER, et al. Oxidized phospholipids, Lp(a) lipoprotein, and coronary artery disease, N Engl J Med: 2005;353:46.Tsimikas S, Bergmark C, Beyer RW, et al. Temporal increases in plasma markers of oxidized low-density lipoprotein strongly reflect the presence of acute coronary syndromes. J Am Coll Cardiol. 2003; 41: 360.Tsimikas, S, Lau HK, Han KR, et al. Percutaneous coronary intervention results in acute increases in oxidized phospholipids and lipoprotein(a): Short-term and long-term immunologic responses to oxidized low-density lipoprotein. Circulation. 2004;109, 3164.Tsimikas S, Witztum JL, Miller ER, Sasiela WJ, et al. High-dose atorvastatin reduces total plasma levels of oxidized phospholipids and immune complexes present on apolipoprotein B-100 in patients with acute coronary syndromes in the MIRACL trial, Circulation: 2004;110, 1406. Walldius G, Jungner I, Holme I, et al. High apolipoprotein B, low apolipoprotein A-I, and improvement in the prediction of fatal myocardial infarction (AMORIS study): a prospective study. Lancet. 2001;358:2026-2033.Yusuf S, Hawken S, Ounpuu S, et al. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study): case-control study. Lancet. 2004;364:937-952.

Platelets are produced in the bone marrow by highly specialized cells called megakaryocytes. The arrow in the image on the right points to a megakaryocyte. The area enclosed by the red circle contains platelets that are created within the megakaryocyte cytoplasm and eventually released. The average lifespan of a platelet is 9-12 days.About 70-80% of a person's total platelets are circulating in the vasculature at any given time. Approximately 20-30% of the total platelets are pooled in the spleen.

Whenever possible, a hallmark of HDFN treatment is to induce labor as early as possible once lung maturity has been attained so that the newborn will be able to survive. Once the infant is born, the main treatment for severe HDFN due to anti-D (and other antibodies causing severe disease) is exchange transfusion. In exchange transfusions, up to 85–90% of the infant's blood can be exchanged with donor blood by a process of removing 5–20 mL of blood at a time, and injecting an equivalent amount until the exchange is complete. An exchange transfusion accomplishes the following: Removes bilirubin and thus helps prevent kernicterus; Removes sensitized red cells that have not been broken down yet; Removes circulating maternal antibody; Provides antigen-negative red cells that will not be destroyed by the maternal antibody, thus will survive and provide oxygen to the tissues.

Serum iron (SI) is a measure of circulating iron bound to transferrin and is reflective of total body iron. SI is elevated in hereditary hemochromatosis (HH) and acute hepatitis. SI is decreased in iron deficiency anemia and chronic inflammation. SI concentrations exhibit diurnal variation, with the lowest values occurring around midnight. In addition, specimens collected from the same individual at the same time of the day may exhibit day to day variations as high as 40%. SI determinations are also affected by diet, menstrual cycle, pregnancy, ingestion of iron supplements, and oral contraceptive use. SI levels alone are considered insensitive indicators of HH. SI is typically measured on automated analyzers using spectrophotometric methods. Iron in the sample is released from transferrin with an acid reagent, reduced to the ferrous state, and reacted with a chromogen such as bathophenanthroline or ferrozine. The intensity of the color change is proportional to the iron concentration. Interference can arise from the use of a hemolyzed sample and contamination of reagents and water with iron. A typical reference interval for SI is 60 - 150 micrograms/dL. SI is usually ordered along with its companion test, the total iron binding capacity (TIBC), or with transferrin (Tf).(2)

Phlebotomy is considered the treatment of choice for patients with iron overload due to hereditary hemochromatosis (HH). Each unit of blood contains approximately 200 to 250 mg of iron. As erythrocytes are removed by phlebotomy, iron stores are mobilized and utilized in the production of new, circulating erythrocytes. Through periodic phlebotomies, stored iron is removed until iron-deficient erythropoiesis is induced. The initial, or iron reduction, phase of treatment typically consists of removing one unit (450 mL) of whole blood once or twice weekly. Prior to beginning phlebotomy, the patient's hemoglobin and hematocrit must be checked to ensure that the patient is not anemic. A sample for serum ferritin is also collected at this time.Initial treatment goals include inducing iron deficient hematopoiesis without the development of debilitating symptoms of anemia. A hemoglobin concentration of 10.0 to 12.0 g/dL is often used as a target range. The initial treatment phase continues until excess stored iron is removed and ferritin levels decrease to approximately 50 ng/mL. (13) Ferritin and hemoglobin levels are periodically monitored during this phase. The number of phlebotomies needed to reduce iron levels and induce anemia is related to the degree of initial iron overload. Patients may be referred to a hematologist or gastroenterologist during the initial treatment phase. Many patients receive therapeutic phlebotomy services in a hospital or doctor's office, but patients may also undergo phlebotomy at a blood center. Blood collected from persons with HH may be used for transfusion or as blood products if it has been collected from a facility with an approved variance from the US Food and Drug Administration. Not all blood centers have applied for or been granted this variance.(14)The initial treatment phase continues until excess stored iron is removed and ferritin levels decrease to approximately 50 ng/mL. Removal of excess stored iron may take from one month to three years.

The bone marrow is structured to provide a suitable environment for developing cells as well as mechanisms for delivering mature cells to the circulating blood. The bone marrow is also capable of increasing production in one or more cell lines when needed.

Those diagnosed with metabolic syndrome are at risk for atherogenic dyslipidemia, a state of abnormal lipids and lipid levels. A state of atherogenic dyslipidemia also enhances the development of atherosclerosis and cardiovascular disease. The increased release of NEFAs and their infiltration of the liver initiate the dyslipidemia process. Increased NEFAs in the liver result in a fatty liver and increased liver triglyceride synthesis. Increased liver synthesis and secretion of very low density lipoprotein (VLDL) follow. VLDL is the lipoprotein that transports triglycerides in circulation. Blood triglyceride concentration then increases.A fatty liver also increases low density lipoprotein-cholesterol (LDL-C) circulating in blood. The predominant lipid in LDL molecules is cholesterol. LDL molecules in the dyslipidemia state are described as small dense LDLs. The increased triglyceride presence causes depletion of the cholesterol and phospholipid content in LDL, making the molecules smaller and denser.Decreased high density lipoprotein-cholesterol (HDL-C) also results. Most researchers believe this is also caused by the increased production of triglyceride-rich VLDL. Decreasing the concentration of HDL molecules is atherogenic in that HDL is the helpful lipoprotein transporting excess cholesterol to the liver and decreasing total blood cholesterol. Higher levels of HDL-C aid in preventing atherosclerosis and cardiovascular disease.

The 2009 H1N1 influenza virus was first detected in the United States on April 15, 2009.The virus was a unique combination of influenza virus genes never previously identified in either animals or people; they were most closely related to swine-lineage H1N1 viruses (hence the designation of "swine influenza"). However, epidemiological investigations of initial human cases did not identify exposures to pigs and it became apparent that this new virus was circulating among humans and not among U.S. pig herds.By April 21, 2009, the Centers for Disease Control and Prevention (CDC) began working on development of a new vaccine effective against this new strain. On April 24, 2009, the CDC uploaded complete gene sequences of the 2009 H1N1 virus to a publicly accessible international influenza database. At the same time vaccine development was occurring, work was also being done at CDC to help laboratories more quickly identify the 2009 H1N1 virus in patient samples. A real time PCR assay developed by the CDC was cleared for use by the Food and Drug Administration (FDA) under an Emergency Use Authorization (EUA) on April 28, 2009.The development of an effective, rapidly performed molecular assay was critical, because a CDC evaluation of non-molecular rapid influenza assays indicated that while these tests were capable of detecting the novel H1N1 strain when present in high concentrations, the overall sensitivity was low. Positive results with these assays were useful, but negative results did not rule out infection with influenza.

Neutrophils have a relatively short life span. They are produced in the bone marrow, and when they reach the band or segmented stages are released into the peripheral blood. They remain there for approximately ten hours before randomly entering body tissues.Neutrophils in the blood stream can be divided into circulating granulocyte pool (CGP) and marginating granulocytic pool (MGP). The white blood cell count reflects the cells in the circulating pool. The cells in the marginating pool move quickly into the circulating pool when needed.During an infection the neutrophil concentration of the peripheral blood can increase almost immediately due to the shift of these cells from the marginating pool and release from the bone marrow storage pool, if needed. Neutrophils then migrate to areas of tissue damage or infection. Neutrophils do not reenter the blood stream from the tissues, thus end their life in the tissues either as a result of phagocytosis or senescence.

Platelets are derived from the cytoplasm of megakaryocytes, giant cells in the bone marrow. At any given time, two thirds of the total platelets are found within the circulation while one third sequestered within the spleen. In persons with enlarged spleens 80-90% of the platelets are in the spleen resulting in a decreased concentration of circulating platelets. In individuals who have had a splenectomy all of the platelets will be in the circulating blood. The life span of the platelet is 8-10 days.

Segmented neutrophils may also be referred to as segs, polymorphonuclear leukocytes, polys and PMNs. Segmented neutrophils are the most mature neutrophilic granulocytes present in circulating blood. Their diameter is approximately 9-15 microns, and their N:C ratio is approximately 1:3. The abundant cytoplasm of a segmented neutrophil is of virtually the same appearance as that of the band. It stains faintly pink and contains numerous fine specific granules which are pinkish-lilac.In order to identify a segmented neutrophil, the cell must have the following characteristics:The nucleus is a deep reddish-purple color, and the chromatin has a coarse, clumped texture.The seg nucleus normally has from 2-5 lobes, with an average of 3.The lobes are connected to each other by a fine filament or strand of nuclear membrane. A filament is a thread-like strip which is so narrow that there is no visible nuclear material between the two sides.

Antibody - A modified type of serum globulin synthesized by lymphoid tissue in response to antigenic stimulus. By virtue of specific combining sites each antibody reacts with only one antigen. Anucleate - Having no nucleus. Azurophilic granules - The well-defined large reddish granules (lysosomes) which may be present in large lymphocytes. They are called "azurophilic granules" because they stain blue with the azure stains which were originally used. Basophilic granules - Specific granules present in the cytoplasm of basophils. These granules are large and stain purple-black due to their strong affinity for basic stain. B-cell - Bone marrow derived lymphocytes which produce humoral antibodies. Biconcave - Having two concave surfaces. Cellular Immunity - The capacity of a small proportion of lymphoid population to exhibit response to a specific antigen. Chromomere - The centrally located granular portion of the platelet. Clone - A population of cells descended from a single cell. Delayed Hypersensitivity - (part of cellular immunity) that develops slowly over a period of 24-72 hours after an antigenic stimulus. It consists of an accumulation of cells around small vessels and/or nerves. Example: Tuberculin skin test reaction. Digestive Enzyme - A substance that catalyzes or accelerates the process of digestion. Eosinophilic Granules - Specific granules present in the cytoplasm of eosinophils. These granules are large, refractile spheres which stain reddish-orange due to their strong affinity for acid stain. Erythrocyte (red blood cell, RBC) - One of the elements found in peripheral blood. Normally the mature form is a non-nucleated, circular, biconcave disk adapted to transport respiratory gases. Fixed Macrophage - A phagocyte that is non-motile. Free Macrophage - An ameboid phagocyte present at the site of inflammation. Graft Rejection - A transplanted tissue that is rejected by the body's antibodies. Graft vs. Host Reaction - A complication that occurs when an implanted piece of tissue, which contains antibodies, rejects the host's tissue. Granulocyte - A leukocyte which contains granules in its cytoplasm, i.e., neutrophilic, eosinophilic, or basophilic granules. Half-life - is the length of time it takes for half of the cells circulating at a given time to leave the blood for the tissues. Hemocyte - Any blood cell or formed element of the blood. Hemostasis - A mechanism of the vascular system to arrest an escape of blood. It involves an interaction between blood vessels, platelets, and coagulation. Heparin - A mucopolysaccharide acid which, when present in sufficient amounts, functions as an anticoagulant by inhibiting thrombin. Histamine - A powerful dilator of capillaries and a stimulator of gastric secretions. Humoral Immunity - Acquired immunity produced after response to an antigenic stimulus in which B cells produce circulating antibodies. Hyalomere - the clear, blue non-granular zone surrounding the chromomere of a platelet. Immune Response - The interaction of a cell and an antigen that results in a proliferation of the cell and a capacity to produce antibodies. Isotonic Fluid - A fluid whose elements have an equal osmotic pressure. Leukocyte (white blood cell, WBC) - One of the formed elements of the blood; involved primarily with the body's defense. Lysosome - A microscopic body within cell cytoplasm; contains various enzymes, mainly hydrolytic, which are released upon injury to the cell. Megakaryocyte - A giant cell of the bone marrow from which platelets are derived. Mononuclear - A cell having a single nucleus.

?Neutrophils have a relatively short life span.They are produced in the bone marrow, and when they reach the band or segmented stages are released into the peripheral blood.They remain there for approximately ten hours before randomly entering body tissues.Neutrophils in the blood stream can be divided into circulating granulocyte pool(CGP) and marginating granulocytic pool (MGP).The white blood cell count reflects the cells in the circulating pool.The cells in the marginating pool move quickly into the circulating pool when needed.During an infection the neutrophil concentration of the peripheral blood can increase almost immediately due to the shift of these cells from the marginating pool and release from the bone marrow storage pool, if needed.Neutrophils then migrate to areas of tissue damage or infection.Neutrophils do not reenter the blood stream from the tissues, thus end their life in the tissues either as a result of phagocytosis or senescence.

TDM provides a quantitative measure of the circulating concentration of a drug. The physician determines if the dosage of the drug needs to be adjusted based on this information.If a drug concentration is determined to be outside the therapeutic range, it may be for one of the reasons listed in the table below. Reason Discussion Noncompliance Patients may (intentionally or unintentionally) not take the drug. TDM can thus help monitor compliance. Dosing errors The dose may have been erroneous or inappropriate given the patient's condition. Malabsorption The TDM result will reveal if the drug cannot be absorbed well through the gut and an alternative route of administration will be needed. Drug interactions Many drugs interfere with the absorption or metabolism of other drugs. These interactions will be revealed by TDM. Kidney or liver disease Any pathology that affects elimination will cause an elevation in a drug level that will be unmasked by TDM. Altered protein binding Changes in serum proteins can lead to big changes in the amount of free drug in serum. Variations in the genetics of drug-metabolizing enzymes can also affect drug concentrations in the body. This is the field of pharmacogenomics that will be discussed later in the course.

Plasma and formed elements stay mixed in circulating blood. When centrifuged (or spun down), blood is separated into plasma, and formed elements including red blood cells. The plasma separator tube shown here has a barrier to maintain separation of plasma and cellular elements during centrifugation and storage. The red cell layer also includes a relatively small amount of platelets and white blood cells, not visible in the photo on the right.

Dimorphic is a term used to describe two circulating red cell populations. One is the patient's basic red cell population while the other is a second population with distinct morphological features. The distinct populations can be observed in the top image on the right. The bottom image on the right illustrates the two distinct peaks that are observed on the RBC histogram from the automated hematology analyzer.Dimorphic red blood cell populations can be found in conditions/situations such as: red blood cell transfusions, myelodysplasia, refractory anemia with ringed sideroblasts, hemolytic processes involving a reticulocyte response, and when patients are given erythropoietin therapy.It is important to recognize when a population of cells in the peripheral smear is not in context with anticipated laboratory findings and the clinical situation.

This peripheral blood smear is from a patient with vitamin B-12 deficiency anemia (pernicious anemia), which results from an inability to absorb the vitamin B-12 needed for DNA synthesis. Since many cells are destroyed in the bone marrow, decreased numbers of red cells are present in the circulating blood, resulting in anemia. However, the red cells that are present are generally macrocytes and are filled with hemoglobin.

Red cell fragments are formed when fibrin strands come in contact with circulating red cells. The strands cut a small piece from the original cell. Several descriptive names have been used for fragmented red cells, depending on the resulting shape of the fragment. These include pre-keratocyte (blister cell), keratocyte (horn cell or helmet cell), and schistocyte (more of a catch-all term). Schistocytes can be seen in disseminated intravascular coagulation (DIC), micropathic hemolytic anemia, glomerulonephritis, and hemolytic anemia resulting from mechanical trauma to the red blood cells (such as severe burns).

In September 2009, the CDC reported that more than 99% of circulating influenza viruses at that time in the United States were the Influenza A 2009 H1N1 strain.In a press briefing December 10, 2009, Thomas Frieden, the Director of the Centers for Disease Control and Prevention (CDC) stated that people under the age of 65 are most impacted by the H1N1 virus. The CDC estimated at the time of the briefing that more than 50 million people in the United States alone had been infected with the H1N1 virus (one in six people). Of this number, more than 200,000 had been hospitalized. An estimated 10,000 deaths could be attributed to the virus, the majority being children and younger adults.The transcript of this press briefing can be accessed at: http://www.cdc.gov/media/transcripts/2009/t091210.htm.Accessed January 17, 2010.On January 14, 2010, Dr Keiji Fukuda, Special Adviser to the Director-Generalon Pandemic Influenza, World Health Organization stated in a press conference that conservatively, about 13,000 people worldwide have died as a result of 2009 H1N1 virus. The transcript of this press conference can be accessed at: http://www.who.int/mediacentre/vpc_transcript_14_january_10_fukuda.pdfAccessed January 17, 2010.

The Epidemiology and Prevention Branch in the Influenza Division at CDC acquires, organizes, and evaluates data and information regarding influenza virus activity year-round in the United States and produces a weekly report for the public to view. This report features the Influenza A 2009 H1N1 virus as well as other seasonal flu strains. The U.S. influenza surveillance system is a collaborative effort between CDC and its many partners in state and local health departments, public health and clinical laboratories, vital statistics offices, healthcare providers, clinics and emergency departments. Information in five categories is collected from nine different data sources that allow CDC to: Find out when and where influenza activity is occurring Track influenza-related illness Determine what influenza viruses are circulating Detect changes in influenza viruses Determine the number of deaths attributed to influenza