Lytic Infections by viruses

Lysogenic infections by viruses

Treating viral infections

Viral Epidemics

Human Viral Diseases

Non-living particle made of proteins, nucleic acids, and sometimes lipids

They can reproduce only by infecting living cellsLytic Infections: virus enters a cell,

multiplies, and causes cell to lyse, or burst, sending new viruses out to infect more cells (SARS, common cold, influenza, rabies)

Lysogenic Infections: viral DNA is inserted into host cell DNA and multiplies w/out harming host cell; causes each new cell to be infected with virus (HIV, Herpes, HPV, shingles)

Viruses are difficult to eliminate b/c their replication pathway requires host cells; drugs are often toxic to the host cell

Also must be grown in live cells and tissues which takes time to do

Methods: vaccinations to provide immunity from infections and antiviral drugs that interfere with viral replication

** viruses mutate rapidly so antiviral drugs must be used only when necessary

Viruses can become resistant quickly

Smallpox among Native Americans: 1492-1900, death toll is estimated at 80-90% of the population

Influenza: 1918-1929 worldwide, death toll approx. 75 million

HIV/AIDS: 1981-present worldwide, death toll approx. 25 million

STD’S: HIV/AIDS, herpes Childhood diseases: measles, mumps,

chicken pox Respiratory diseases: influenza,

common cold Skin diseases: shingles, warts Digestive tract diseases: gastroenteritis Nervous system diseases: polio, viral

meningitis, rabies Other diseases: smallpox, hepatitis

7 APRIL 2013 - As of 7 April 2013 (16:30 CET), the Chinese health authorities notified WHO of an additional three laboratory-confirmed cases of human infection with influenza A(H7N9) virus.

To date, a total of 21 cases have been laboratory confirmed with influenza A(H7N9) virus in China, including six deaths, 12 severe cases and three mild cases.

The Chinese government is actively investigating this event and has heightened disease surveillance.