The role of genetics in influenza is not well researched, but it may be a factor in influenza mortality. Epidemiology
Influenza is typically characterized by seasonal epidemics and sporadic pandemics. Most of the burden of influenza is a result of flu seasons caused by IAV and IBV. Among IAV subtypes, H1N1 and H3N2 currently circulate in humans and are responsible for seasonal influenza. Cases disproportionately occur in children, but most severe causes are among the elderly, the very young, and the immunocompromised. In a typical year, influenza viruses infect 5–15% of the global population, causing 3–5 million cases of severe illness annually and accounting for 290,000–650,000 deaths each year due to respiratory illness. 5–10% of adults and 20–30% of children contract influenza each year. The reported number of influenza cases is usually much lower than the actual number of cases.During seasonal epidemics, it is estimated that about 80% of otherwise healthy people who have a cough or sore throat have the flu. Approximately 30–40% of people hospitalized for influenza develop pneumonia, and about 5% of all severe pneumonia cases in hospitals are due to influenza, which is also the most common cause of ARDS in adults. In children, influenza is one of the two most common causes of ARDS, the other being the respiratory syncytial virus. About 3–5% of children each year develop otitis media due to influenza. Adults who develop organ failure from influenza and children who have PIM scores and acute renal failure have higher rates of mortality.
Splenic infarction is a condition in which blood flow supply to the spleen is compromised, leading to partial or complete infarction (tissue death due to oxygen shortage) in the organ. Splenic infarction occurs when the splenic artery or one of its branches are occluded, for example by a blood clot.In one series of 59 patients, mortality amounted to 5%. Complications include a ruptured spleen, bleeding, an abscess of the spleen (for example, if the underlying cause is infective endocarditis) or pseudocyst formation. Splenectomy may be warranted for persistent pseudocysts due to the high risk of subsequent rupture. Diagnosis
Although it can occur asymptomatically, the typical symptom is severe pain in the left upper quadrant of the abdomen, sometimes radiating to the left shoulder. Fever and chills develop in some cases. It has to be differentiated from other causes of acute abdomen. An abdominal CT scan is the most commonly used modality to confirm the diagnosis, although abdominal ultrasound can also contribute. Treatment
There is no specific treatment, except treating the underlying disorder and providing adequate pain relief. Surgical removal of the spleen (splenectomy) is only required if complications ensue; surgical removal predisposes to overwhelming post-splenectomy infections. Causes
Several factors may increase the tendency for clot formation, such as specific infections (such as infectious mononucleosis, cytomegalovirus infection, malaria, or babesiosis), inherited clotting disorders (thrombophilia, such as Factor V Leiden, antiphospholipid syndrome), malignancy (such as pancreatic cancer) or metastasis, or a combination of these factors.