The Coronavirus Disease-19 (COVID-19) pandemic is currently a priority for health services worldwide. Unlike the Severe Acute Respiratory Syndrome-Coronavirus (SARS-CoV) epidemic in 2012, the COVID-19 shows specific alterations in the white blood cell count, accentuated in severe cases, and with respiratory failure. Among the most relevant data are both lymphopenia, thrombocytopenia, and eosinopenia. The Neutrophil Lymphocyte Index has been beneficial in the evaluation of infectious respiratory processes, showing a sensitivity similar to scales such as CURB65 (Confusion, Uremia, Respiratory rate, BP, age ≥ 65 years). Because COVID-19 infection shows alterations in the blood cell ratio, these indices may be useful in evaluating patients with COVID-19 infection.

The hematological alterations in patients with COVID-19 divided into two aspects: the main ones, the global leukocyte count, and the individual counts. Most of the information about the behavior of blood counts come from cases attended in Wuhan, China. At the Zhongnan Hospital in Hubei Province, identified that the lymphocyte count was lower in critically ill patients. At the same time, the leukocyte counts were higher in deaths associated with COVID-19, this elevation being mainly of neutrophils. The lymphopenia is also a constant data in COVID-19 (47.4%), especially in cases that entered the Intensive Care Unit. As in community pneumonia, severe lymphopenia has associated with a high risk of death. A relationship between neutrophils and lymphocytes is called the Neutrophil-Lymphocyte index. This index is especially useful for predicting respiratory complications, such as for COVID-19, where mortality ranges from 2-9% compared to the 2012 epidemic (10%) or Middle East Respiratory Syndrome (37%). In Mexico, there is a high prevalence of chronic diseases that increase the risk of COVID-19 infection. This study's main objective is to identify the association of blood abnormalities on respiratory complications associated with COVID-19 infection. All data were obtained from the clinical records of patients treated by COVID-19.

Inclusion Criteria:

• Patients with active COVID-19 infection

Exclusion Criteria:

• Liver failure
• Active cancer
• Chronic renal failure
• AIDS
• Pregnancy

Mexican patients diagnosed with active COVID-19 infection who require hospital care and who have peripheral blood counts at diagnosis.

All participants and their information will be managed by intern investigators and will be kept secure for personal data protection according to Mexican laws