SARS.

For this post, I would like to share with readers about SARS and coronavirus infections. Coronavirus is the virus that can cause Severe Acute Respiratory Syndrome. Basically, coronavirus can cause common cold (10 – 35%), with high prevalence of the disease in late fall, winter and early spring. SARS is an outbreak that occurred in 2002-2003. This new emerging disease is originated from Southern China that may be caused of human contact with infected animals such as palm civet, racoon dog or ferret badger. However, these animals are not the natural hosts for this virus. Horseshoe bat is thought to be the natural host.
Basically, the disease transmission can occur by several methods such as large and small aerosols as well as through fecal-oral pathway. Sneezing, coughing, and contact with secretes containing virus can lead to infection.
Pathogenesis of this virus begins with the attachment of virus to respiratory epithelial cells via angiotensin converting enzyme 2 receptor. The virus can disseminate systemically and can be found in blood, urine and stool (up to 2 months). It does not only cause serious lung infection but spread to other organs as well including liver.  In respiratory tracts, viral replication can lead to the damage of epithelial cells. Other than that, chemokines and interleukins are released as well in response to the damage. Other changes include hyaline membrane formation, desquamation of pneumocytes in alveolar spaces and infiltration of monocytes and lymphocytes. Virus usually persists in respiratory tract for about 2 – 3 weeks.

The incubation period of SARS is between 2 – 7 days in average. The clinical manifestation of SARS include high fever, followed by malaise, myalgia, and headache and followed by non productive cough after 1 – 2 days (first week). Some people develop diarrhea. In X-ray examination, we can see patchy consolidations that are frequently seen in lower lobes and peripheral lung regions or interstitial infiltrates. These can progress toward diffuse involvements. In second week, usually the conditions get worst with multi-organs involvement. Adult Respiratory Distress Syndrome may develop. Age more than 50, hepatitis, diabetes, and cardiovascular disease are the risk factors of developing severe form of disease.

The diagnosis of SARS can be confirmed by real time RT-PCR from respiratory tracts specimen and plasma early in the disease and from other specimen such as urine and stool after a week of the disease, tissue culture by using Vero E6 cells as well as serology test. In serology test, antibodies toward virus can be detected within 28 days after disease after the onset of illness. Other lab test that can be performed is blood test. In SARS, we can find lymphopenia with CD4 + T cells are the largest cells affected rather than CD8 + T cells and NK cells.  Thrombocytopenia can also be observed in as the disease progress.

The treatment include supportive treatment such as mechanical ventilator, IV infusion, immunomodulatory such as use of corticosteroid to prevent pulmonary fibrosis and other measures.

In conclusion, prevention of this emerging disease is simple. Hand washing and increased awareness of both infected person and community is needed to reduce the impact of epidemic or pandemic.

References:1. Fauci. Et al. Common Viral Respiratory Infections and Severe Acute Respiratory Syndrome (SARS). Harrison’s Principles of Internal Medicine. 2008.
 2. dr. Titik Nuryastuti Lecture Notes on The Emerging Disease Avian Influenza and Coronavirus/SARS. 2010.