Infection transmission

 The COVID-19 pandemic should have got us all thinking about infection transmission and control.  Yet, the virus continues to spread.

I remember the pretty much the first laboratory class we did in Microbiology 101 was a demonstration of how infection transfers within a community.  There were 24 students in the class.

First, everyone wiped their hands with a paper tissue, one of which had been contaminated with a bacterial culture.  This organism was Serratia marcescens, which produces a bright red pigment when grown under the right conditions.  A sequence grid was set up, so that everyone shook hands with one other class member and then plated their hand onto an agar plate.

The second round of hand shakes was then undertaken with different class members, without first washing our hands, and, again, hands were plated.  This sequence continued until, by the end, everyone had shaken hands with about 10 classmates and plated their hands.

The plates were incubated, and a couple of days later were examined for the presence of the bright red colonies.  Scoring the positives against the sequence grid, it was very obvious how the infection had spread throughout the class.  Not everyone became infected initially, but the infection spread exponentially and after six rounds, everyone in the class was positive.

How is this relevant to COVID-19 spread?  This virus is supposedly spread predominantly by droplet inhalation.  However, an individual may become infected by touching their face with infected hands or perhaps by rubbing their eyes.  The virus, like the Serratia, might be picked up on the hands from surfaces like door handles, wash basin surrounds, pens, or from shaking hands with a carrier etc.  "OK, I don't touch my face and eyes".  Are you sure?  I used to lecture to classes of up to 130 students and occasionally counted how many were touching their face at any one time.  (Yes, I know, I had put half of them to sleep and their heads were in their hands).  Up to 60% of the class touched their faces and noses and eyes.  A similar surreptitious survey found that up to 30% of students left the toilets without washing their hands!

The take-home message here is - "Wash and sanitise your hands regularly - many times a day; avoid hand shaking and kissing 😞 and if you are sick, STAY HOME.  In fact, if you don't have to mix with people, stay away from them."  Like in our first year experiment, there was no indication that any particular person was carrying the infection until two days later when the test results were available.

Update:  As of today, 10th July 2021, we have seen over 4 million people die of COVID-19 around the world and it is now obvious that the primary route of transmission is by inhalation of virus particles.  Mask wearing significantly reduces the spread of the virus by trapping droplets and by wearing a mask, you are protecting others.  In countries where people still gather together in crowds, the virus is spreading very fast and the delta variant, which is highly infectious, is ripping through the population.

If you are reading this update and you have the option, please GET VACCINATED, both for your own safety and the protection of your friends and family.

Safe Food in Lockdown

Are you tired of reading and hearing about COVID-19 yet?  Are you totally confined to your home, or are you an essential service worker?  How have things changed for you?

My on-line news service provides the ten top items each day as links.  For the last two weeks, nine out of the ten have been about COVID-19 and mostly they provide depressing reading.  I'm not going to rehash all that.

New Zealand, where I live, has closed its borders. 

The majority of shops are closed, so our food shopping is mostly confined to visits to the supermarket, which may involve long queues and limited numbers of people in the building at any time, so the on-line ordering and collection option is popular. The 2-metre separation rule is now being followed by most people.

How does this affect our eating habits?  Well, restaurants and fast food joints are closed, so we are all preparing many more meals at home from what we have on hand.  This may involve substitution of ingredients, or complete change of menu at short notice.  Not everyone is used to cooking meals at home and there may be a few disasters! 

Do we need to worry about contracting the virus from our food?  The best information I have is that this is a respiratory infection and you can't pick it up from food.  Since it is a virus, it can't replicate in stored food, so the only concern is with contamination of the packaging.  Survival time on surfaces seems to vary, but studies by CDC, researchers at various universities and FDA indicate that the survival time varies from a few hours to about three days, but it is important to remember that the AMOUNT of virus remaining may be as low as 0.01% of the original contamination.  It is unlikely that you can contract the virus from food packaging, but it's a good idea to wipe the packaging down with a 1:48 dilution of household 6% bleach, (5mL 6% bleach into 240mL water) or just leave the packages unopened for a few days.

So, do we need to change our cooking and eating habits?  Essentially, I think the answer is "No" but we do need to be very careful.  Nobody wants to waste food, so it's likely that leftovers will be stored for future use.  We don't want to burden our hospitals with food poisoning cases.  Here are a few tips:

Keep leftovers refrigerated and reheat to at least 75C - use a thermometer
Wash your hands thoroughly and frequently
Don't touch your face
Ensure that food is cooked properly (as you would normally) 
Be very wary of cross contamination of raw and cooked food
Stay home; don't pop down to the corner store just to pick up a bottle of milk - plan your shopping.

Just a couple of final points:
The experts now think that the wearing of masks available to the general public is not going to protect you from infection.  Don't forget that the virus is tiny and if you get it in your eyes, it will run down your tear ducts into your nasal passages and can initiate an infection

I am now washing my hands more thoroughly and frequently than when I was working with green lipped mussels deliberately infected with high levels of Salmonella!

Hand washing is REALLY important

According to a post on Stuff, a worker at a Silver Fern Farms meat plant in New Zealand lost her job for not washing her hands.

At first sight, this may appear to be a draconian decision, but the company had written procedures in place, stating that if a worker touched dropped meat, they should wash their hands before handling other meat being prepared for packaging.  Meat that has fallen onto the floor can be contaminated by many different bacteria and by other organic material.  Handling this fallen meat and the area around the dropped meat table could contaminate the worker's hands and hence other meat being packaged.

If the worker had been properly inducted into the plant, she would have been made aware of the requirement to wash hands after retrieving meat from the floor and transferring it to the dropped meat table.

The real problem is that the company has a meat export licence that almost certainly has stringent hygiene requirements incorporated.  Thus failing to observe the written procedures in relation to dropped meat could have put the licence, and the livelihoods of all other workers at the plant, at risk.

Survival in Antarctica

I hesitate to write this blog article in case someone misinterprets it.  So... DO NOT TRY THIS AT HOME!

I recently spent three weeks in the Taylor Dry Valley in Antarctica.  Conditions are relatively harsh, though we had excellent extreme cold weather gear, warm tents and double layer sleeping bags.  Approximately 19 scientists and several visitors, who stayed for a couple of days, shared a Polar Haven working tent - insulated wooden floor and heated by a diesel stove, with electrical power provided by a generator.  Conditions in the tent were quite crowded; we ate our meals in there, operated scientific instruments, and analysed data.

What does this have to do with food safety?

There is no opportunity to bathe or even wash hands and only the most primitive sanitation facilities are available.  Baby wipes are the main means of keeping clean.  Nineteen individuals cooked for each other and ate together.  We ate all meals with our own cutlery and plastic food bowls and all drinks were contained in thermally insulated cups. Washing up consisted of a wipe with a paper towel or a non-scented baby wipe.  Because of the extremely dry conditions, we attempted to drink 4 litres of water every day, and all water came from Spaulding Lake, which is fed from the glaciers.  (Incidentally, the water tastes wonderful!)  Everyone carried their own 1 litre drink bottle.

Nobody contracted food poisoning.  I had both a personal and a professional interest in this!

This feat was the result of a combination of extreme personal hygiene care, the environmental conditions, and our diet.

In our Antarctic Skills Training programme, the importance of personal hygiene was emphasised - the Taylor Valley is very isolated and not a place to get sick.  Besides the use of baby wipes, tubes or pump dispensers of hand sanitiser were available everywhere and most team members carried their own supply too.

All our food, other than the dehydrated material, was stored outside in insulated boxes in the shade.  The mean ambient temperature was around 0C, so no opportunity for bacterial multiplication.

Our meals were either hot - bacon, pasta, meat stew, risotto, hashbrowns (lots), curry etc. -  or preserved in some way, such as dried and canned - cereals, canned fruit, milk powder, biscuits, soups, chocolate, muesli bars, peanut butter, jam, hard cheese, English muffins etc.  Most meals therefore were cooked in the outside camp kitchen and eaten immediately.  There were never any leftovers or reheating, so again no opportunity for bacteria to multiply or produce toxin.

I don't recommend that anyone should eat or prepare food for others without washing their hands, but this experience does show that with the proper precautions, it is possible, even in primitive conditions, to maintain food safety.

Odd Spot:  Perhaps the highlight of our 3-week deployment in Taylor Valley came the day after we ran out of meat.  Two of the helicopter pilots secretly organised to bring 4 or 5 large pizzas on one of the resupply missions.  They were heroes!

TV chefs fail at basic hand hygiene

I have just watched famous TV chefs preparing demonstration dishes.  One worked in his kitchen, others in an outside setting.

In both cases, the chefs were handling raw meat with their bare hands and preparing salads and sauces.  At no point did the chefs wash their hands and of course, they were moving between raw meats, fresh vegetables and spices. 

Of most concern to me was the use of a towel.  Chefs often have a towel at their waist; they use it for wiping spills from plates prior to service.  On this occasion, the chef handled the raw meat and repeatedly wiped his hands on the towel.  The sauce was blended from fresh vegetables and was not cooked.  There were no hand washing facilities in the shot and the sauce vegetables were also handled with bare hands.  The potential for food poisoning is significant.

Now, perhaps the chefs really did wash their hands between handling raw meats and salads.  However, these are demonstrations for ordinary viewers.  They should be setting a better example and emphasising the necessity of hand washing.

Telecom turtle might bring more than increased sales

A recent series of adverts for Telecom in New Zealand features a young boy and his pet turtle.  The adverts are quite funny and obviously are appealing to adults and children alike.  They may even result in more sales of cellphones.  Apparently, a side effect of this advertising is greatly increased sales of turtles, which are now practically unobtainable, according to the 3-News this evening.

If you have bought a baby turtle, or are given one for Christmas, make sure that you wash your hands carefully after handling it and that children are instructed on hygiene - touching or kissing turtles (why would you?) might result in a Salmonella infection.  Don't forget that the infecting dose for Salmonella may be quite small and the bacteria are easily transferred from hands to mouth.  I'm not sure of the incidence of Salmonella in turtles in New Zealand, but in America, there is a high frequency of carriage in baby turtles, with a concomitant infection rate in children.

Be careful out there, folks.

Food Safe Families: Does it Prevent Contamination of Foods? Guest Editorial

Patricia Walling^*

In just about any news medium, headlines about recalls of meat, poultry and produce due to contamination occur with deadly regularity. Sadly as anyone in health care knows these headlines aren't just hype; food borne diseases can be fatal. This is especially true when they infect the very young, elderly and those with compromised immune systems.

According to the Center for Disease Control and Prevention (CDC) “each year, 1 in 6 Americans, or 48 million people get sick, 128,000 are hospitalized and 3,000 die of food borne diseases.” The agency notes that among the 31 known food borne pathogens, the leading causes of deaths and hospitalization are: Salmonella, Toxoplasma, Listeria, norovirus and Campylobacter.

Based on this public health problem, a partnership was formed among several U.S. governmental agencies (including the U.S. Department of Agriculture, the Department of Health and Human Services, the Food Safety and Inspection Service, Food and Drug Administration and the CDC) that are charged with keeping the food sources safe in conjunction with the Ad Council. The campaign, recently announced by the USDA, is titled “Food Safe Families.”

These organizations feel that this promotional effort will “shift the way people think about food handling so they can take a more proactive approach at home to help reduce food-related illnesses.” However, not everyone feels this educational and health promotion campaign will do much to solve the real challenges of the food distribution system.

The Food Safe Families Program

Public service campaigns, created by U.S. governmental agencies have a storied history. From the iconic U.S. Forest Service and Ad Council campaign that featured Smokey Bear admonishing that: “Only you can prevent forest fires” (launched in 1947), to the FDA’s “Food Pyramid” (first launched in 1992, updated in 2005 and then replaced in 2011), there have been hundreds of public service campaigns that are well-meaning but often ineffective.

Will the Food Safe Families campaign have the promotional “legs” of Smokey Bear’s message or join “Just Say No” campaign as a waste of taxpayer money? Only time will tell. However, the campaign includes several aspects that make it important.

According to the USDA Food Blog, “using the motto “Check Your Steps,” Food Safe Families aims to get consumers to adopt four very easy steps when preparing food:

1. Clean: Clean kitchen surfaces, utensils and hands with soap and water when preparing food.

2. Separate: Separate raw meats from other foods by using different cutting boards.

3. Cook: Cook foods to the right temperature by using a food thermometer.

4. Chill: Chill raw and prepared foods promptly.”

These four steps – clean, separate, cook and chill – serve as the graphic and messaging platform of the campaign. The agencies hope that by constantly reiterating this message, it will become ingrained in those who are charged with preparing the family meals.

Even the timing of the launch was important. The agencies choose Jun. 28, 2011, because this is the start of summer and represents the prime outdoor grilling season for most families. The USDA noted in its blog that “food borne illnesses tend increase with more outdoor meals.”

Once the campaign was launched, it seemed that Food Safe Families had covered most of the promotional bases. There were spiffy new graphics, memorable message points, an innovative social media campaign and public service media all up and running. The timing and execution of the campaign was excellent, until people started showing up in emergency rooms with symptoms of Listeriosis.

The Listeria Outbreak

Jensen Farms, located in Holly, Colorado grows and ships cantaloupes throughout the United States. After numerous reports of an outbreak of Listeriosis, the FDA and CDC traced the contaminated melons back to this farm. According to a news update from the FDA on Sept. 30, 2011, “the cantaloupes were produced from the end of July to Sept. 10, 2011. Given that the Jensen Farms’ recall has been in effect for more than two weeks, it is expected that all of the recalled whole Jensen Farms cantaloupes have been removed from the marketplace.”

The website for the Mayo Clinic notes that “Listeria infection is a food-borne illness that can be very serious for pregnant women and people with impaired immune systems. Listeria bacteria can survive refrigeration and even freezing.” As of Oct. 1, 2011, the CDC reported that the contamination had been responsible for the deaths of 17 people and the illness of 84 across 19 states.

In response to this outbreak, the FDA noted that “It is very important that consumers clean their refrigerators and other food preparation surfaces. Consumers should follow these simple steps:

• Wash hands with warm water and soap for at least 20 seconds before and after handling food.

• Wash the inside walls and shelves of the refrigerator, as well as cutting boards and countertops.

• Wipe up spills in the refrigerator immediately and clean the refrigerator regularly.

• Always wash hands with warm water and soap following the cleaning and sanitization process.”

Do These Guidelines Prevent Food Borne Illness?

For all of the regulations, safeguards, inspections and, yes, public service campaigns, the growers and processors of food employ humans and sometimes they get careless and make mistakes. Such is also the case with homemakers.

In cases where these mistakes cause deadly diseases to spread, the Food Safe Families campaign could help to ameliorate the damages from contaminated cantaloupes, ground meat, peanut butter or any other food. However, it will have no effect on preventing the disease from starting. That involves many other factors. These include: the distance and the number of companies that must handle food between the farm and family and the quantity and quality of the inspections along the distribution channels.

Given time, the Food Safe Families campaign could have a positive impact on the health of U.S. citizens. Even now, the use of the social networks that were launched for this campaign have served as valuable tools to help with the dissemination of information about the latest contamination. However, such programs as buying foods that are produced closer to home may have more impact.

*  Patricia Walling

Patricia Walling is a web content designer for several healthcare-related sites. She self-identifies as a perpetual student of medicine, and can be found most of the time researching anything
related to the field. She lives in Washington, and as a result loves the long winters.

 

Don’t read this if you have a weak stomach

The reason for the title will become apparent later on!

People who have an opportunity to influence the public have a duty to make sure they know what they are talking about and to think about the consequences of their comments.

Last week, popular TVNZ breakfast show host Paul Henry was talking about the state of cleanliness in public toilets. The breakfast show is a mixture of news, views and entertainment and Paul made a meal (if you’ll pardon the pun) of the issue, drawing out as much toilet humour as possible. Unfortunately, he also claimed that washing your hands in a public convenience would result in your hands being more contaminated than if you had not bothered.

This is hard to stomach. Certainly, taps and door handles may be contaminated, often with faecal bacteria and it may be that soap and soap dispensers are also contaminated. However, I find it difficult to accept that not washing hands is better than washing.

If you didn’t take the earlier warning, now is the time to quit reading.

If you have wiped your backside with toilet tissue, then the chances are that your fingers are contaminated with faecal bacteria and viruses. Way back when I started teaching food microbiology, I used to run an exercise with my students. They took various numbers of sheets of toilet tissue and placed them over a finger end, which they then gently wiped across a Petri dish of indicator bacteria. These, as it happens, were Escherichia coli, the bacteria always present in the gut. These bacteria have the ability to produce a green metallic sheen when they grow on an agar called Eosine Methylene Blue. Since they occur only in the gut, we should not normally expect to find them on our hands, except for the obvious reason. After the wiping phase of the experiment, the tissue was discarded and the same finger pressed onto the EMB agar, which was then incubated overnight. The students then washed their hands and dried them before making a further agar impression.

The students were usually horrified to discover that even when using 6 sheets of 2-ply toilet tissue, their finger impressions often grew bacterial colonies with a green metallic sheen. Now, not to put too fine a point on it, 6 sheets is an almost unmanageable wad of paper! Washing usually removed all the bacteria, but only if soap and warm water were used.

There are several messages here.
• No matter how much tissue you use, you can’t be sure that you won’t have faecal bacteria and viruses on your fingers.
• Washing your hands with soap and then drying them will remove most of the bacteria

Unfortunately, when you turn on the tap with contaminated hands, they will transfer bacteria and viruses to the tap. After you have washed, you recontaminate your hands when you turn the tap off. That’s why in hospitals and laboratories the taps have long handles that can be operated with wrists or forearms, or are operated by foot pedals or infra-red sensors. These days, many washroom taps have press buttons that allow the water to run for only 30 seconds or so and don’t need to be turned off.

So what can you do?
• Turn the tap on with your wrist
• Wash your hands thoroughly with soap (sing “Happy birthday" to yourself twice to ensure you wash for long enough)
• Thoroughly dry your hands on a paper towel and then use it to turn the tap off
• If the washroom has blower hand dryers, be careful not to touch the machine (if it has an on button, push it with your knuckle)

Watch a microbiologist in a washroom. When I go in there, I do all the above and then open the door with the crook of my little finger. It’s not foolproof, but a lot better than not washing. If you are still paranoid, buy a small spray bottle of hand sanitizer and carry it in your bag for use after you have left the washroom and before you eat.

I hope you read this far, Paul.

Hand washing not allowed

I hope that all of us in the food industry know just how important hand washing is. If done properly, using hot water and soap, working on all the fingers and paying attention to nails, then rinsing and drying thoroughly, it can significantly reduce the amount of bacterial contamination on the hands. Indeed, there is evidence that clean hand contact with food is far less hazardous than contact from a gloved hand if the operator is not careful about glove use.

Rotavirus infections are highly contagious and commonly affect young children. The main symptoms are watery diarrhoea and vomiting, carrying the risk of dehydration. The outbreaks are often seen in kindergartens and schools. As with all gastrointestinal infections, the main route of infection is directly from improperly washed hands or through contact with contaminated surfaces and toys. The virus is resistant to the environment and to disinfection and will survive on surfaces for a long time, so toilet facilities used by children with watery diarrhoea are obvious transfer points. The time between infection and appearance of symptoms varies from 1 to 3 days.

OK – so what set me off on this lecture? My daughter in law has just had a new baby and we are obviously very aware of the potential for infection during her first few weeks of life. My son, (he’s an engineer but grew up being indoctrinated about food safety) informed me that there is an outbreak of diarrhoea at his children’s school. He has provided the girls with an alcohol hand wash to use at lunchtime, because apparently the children ARE NOT ALLOWED TO WASH BEFORE LUNCH. What kind of education for life is that?