Coronaviruses and Noroviruses

3/29/13

Coronaviruses

Have crown or halo appearance

Crown is made of glycoprotein E2 which binds host cell.

Has large + RNA genome 25-30K bases

Enveloped virus

Very, very durable for enveloped virus.

Causes approximately 10% of cold-like illnesses

Usually limited to upper respiratory tract by temperature

Occasionally may cause mild viral gastroenteritis

Not deemed a serious human pathogen until 2003

SARS-Sudden Acute Respiratory Syndrome

Outbreak began in Guangdong province of China

Spread to Hong Kong and Canada

8100 recognized cases

770 deaths

Caused by SARS CoV

First case of current molecule genetics at work in current disease.

Virus was identified and genome sequenced within one month

Patients die of pulmonary edema caused by cytokine storm.

Glycoprotein E2 binds to ACE2 receptor in respiratory and GI tracts as well as sweat glands.

Unclear whether virus can spread through sweat

Second, minor outbreak in China in April 2004

Limited number of cases of SARS since

Noroviruses

Similar to picornaviruses

+ RNA of approximately 7500 bases with Vpg attached

Naked capsid that is very durable

Virus can persist for several days in the environment

Norwalk and Norwalk-like viruses are most common pathogens

Cause 30-50% of viral gastroenteritis

The virus can persist in low pH, high and low temp, chlorine, and detergents so it can be spread by a variety of transmission routes.

Contaminated food or water is most common.

People shed virus 10-14 days after symptoms stop

Food preparation workers may contaminate food after having an illness

Several major outbreaks on cruise ships have been linked to a single kitchen worker

Diseases are marked by cramping and diarrhea with nausea and vomiting. Many people have headaches 3-4 days after symptoms begin.

Hydration and rest are best treatments

Disease normally resolves after 2-5 days.