Changing pathogens.Lesson Objectives

To describe how antibiotic resistance may occur through natural selection.

To evaluate the consequences of mutations in relation to epidemics and pandemics.

Are these pathogens caused by a virus or a bacteria?

List of pathogens• TB

• Flu

• HIV

• Salmonella

• Herpes

• Chicken pox

Are they bacterial or viral.

Are these pathogens caused by a virus?

List of pathogens• TB

• Flu

• HIV

• Salmonella

• Herpes

• Chicken pox

Are they bacterial or viral.• Bacterial

Are these pathogens caused by a virus?

List of pathogens• TB

• Flu

• HIV

• Salmonella

• Herpes

• Chicken pox

Are they bacterial or viral.• Bacterial

• Viral

Are these pathogens caused by a virus?

List of pathogens• TB

• Flu

• HIV

• Salmonella

• Herpes

• Chicken pox

Are they bacterial or viral.• Bacterial

• Viral• Viral

Are these pathogens caused by a virus?

List of pathogens• TB

• Flu

• HIV

• Salmonella

• Herpes

• Chicken pox

Are they bacterial or viral.• Bacterial

• Viral• Viral

• Bacterial

• Viral

Are these pathogens caused by a virus?

List of pathogens• TB

• Flu

• HIV

• Salmonella

• Herpes

• Chicken pox

Are they bacterial or viral.• Bacterial

• Viral• Viral

• Bacterial

• Viral

• Viral

WHY SHOULD A COURSE OF ANTIBIOTICS ALWAYS BE COMPLETE?

Antibiotic resistance by natural selection

Antibiotic 2 given – only those bacteria that are resistant survive to breed

Now bacteria are resistant to two antibiotics

Antibiotic 1 given – only those bacteria that are resistant survive to breed

Bacteria – a few will have mutations that make them resistant to antibiotics

Epidemics Epidemics B1a 4.4 B1a 4.4 How can we protectHow can we protectourselves against bird ourselves against bird

flu? flu?

Flu WarsBird flu is a disease which affects millions of birds around the world. In a few cases the virus has jumped species and affected humans. The bird flu virus exists in a number of forms and the H5N1 variant is particularly dangerous to birds AND humans - around half of the people who contract the disease die within 48 hours.

What can be done? Scientists all over the world are now searching for a vaccine against bird flu. It’s a race - and if the virus mutates into a form which can be passed from person to person BEFORE we have a suitable vaccine, millions of people could die.

The race for a vaccineThe race for a vaccine

23 Mar 1996

14 Sep 1996

22 Aug 1997

21 Jan 2004

10 Mar 2004

17 Oct 2004

Travel Advice

The following screens highlight critical dates of the Bird Flu virus

23 March 1996Bird flu confirmed in Hong KongScientists confirmed that many of Hong Kong’s domestic birds were infected with the so-called bird flu. This is not a major problem because it does the birds little harm and does not infect humans. Wild birds carry the disease around the globe anyway.

14 September 1996The dangers of mutationThe bird flu currently infecting chicken all over South East Asia is the low virulence form. It produces some feather drop and fall in growth rate but rarely does significant damage. It is one of the H5 types of the virus. So why is this dangerous?H5 viruses have been known to mutate into the much more dangerous high virulence form. This spreads rapidly through the chicken population and can cause death - sometimes in as little as 48 hours!Dr N Chen from the Public Health Authority confirmed earlier today that the type of virus infecting birds in the area was the H5N1 variant.

22 August 1997 Vaccine conferenceMedical scientists confirmed at a conference today that the virus involved in the latest flu outbreak was the H5N1 variant. Researchers from Hong Kong university gave details of their plans to develop a vaccine in case the disease spreads. One problem is the time it takes to produce vaccines.

Identify the virus and its type.

Grow the virus in conditions which weaken its ability to cause disease.

Inject the weakened viruses into cells (possibly animals or in cell culture).

Cells produce antibodies which can destroy the virus

Test the weakened virus for safety in humans.

If the test is successful, the vaccine is safe and encourages antibody production in humans, mass produce it.

Distribute the vaccine to endangered areas and organise a vaccination programme.

Making a new vaccineMaking a new vaccine

21 Jan 2004Bird flu epidemic in 8 countries The World Health Organization confirmed today that H5N1 flu outbreaks are now occurring in 8 countries at the same time. This has not happened before and is causing some concern. Over 150 million birds have been destroyed to try to control the outbreak - so far with little success. The countries affected are: Indonesia, Vietnam, Cambodia, Laos, China and Thailand.

10 Mar 2004Killer flu jumps to humans! Of the 35 people who have contracted H5N1 bird flu since the recent outbreak 24 have died. Doctors fear this could be the beginning of a major flu pandemic. The very young and the old are particularly susceptible to the disease.

17 Oct 2005Bird Flu could kill 50,000!If the H5N1 virus develops the ability to pass easily from human to human we could be looking at 50,000 excess deaths this winter. We cannot guarantee this will happen but we cannot be sure it will not. Now is the time to start taking precautions.

Creating a vaccine normally takes a long time. A new Creating a vaccine normally takes a long time. A new technique, not yet tested in humans, could produce a new technique, not yet tested in humans, could produce a new

DNA vaccine in a few weeks.DNA vaccine in a few weeks.

Identify the virus type - in this case H5N1

Find the DNA that produces the H5N1 proteins in the virus coat

Inject the DNA into cells. They start to produce the H5N1.

The body’s natural immune system produces antibodies which react with the proteins.

If the real virus then gets into a cell the antibodies are produced very rapidly and the virus is destroyed.

This advice is from the Foreign and Commonwealth Office website. Explain how the advice here will help to protect you from bird flu.

There are no specific restrictions for travellers to any of the countries affected by avian influenza, as the risk is believed to be very low. But if you plan on travelling to areas where outbreaks have been reported, you should seek expert medical advice before departure, check on latest travel advice and take the following precautions:

•Avoid visiting live animal markets, poultry farms and other places where you might come into contact with wild, domestic or caged birds•Avoid contact with surfaces contaminated with animal faeces or fluids•Do not eat or handle poultry, egg or duck dishes, if any of these are undercooked or raw•Wash hands regularly•Do not attempt to bring any live poultry products back to the UK

Most human cases are thought to have acquired their infection following exposure to dead or diseased birds. Evidence suggest that particularly risky exposure occurs during the slaughter, plucking and preparation of poultry for cooking. You should not eat dishes made with fresh duck blood or any other raw or inadequately cooked poultry or egg products. Normal cooking destroys the avian influenza virus. No cases of avian influenza have been linked to the consumption of properly cooked poultry and egg products.