Prevention of infections aboard cruise ships

Spring break is here many Americans will go on vacation and some will take a cruise.

Cruises have become increasingly popular over the years as a form of vacation. Cruise lines have responded to the increased demand by adding larger ships to meet the demand. On the darker side cruise ships have been plagues by risk of infection outbreaks due to the over crowding aboard ships. The cruise lines have appropriately responded to this fear of outbreaks by instituting appropriate precautions without interfering with the vacation mood. In fact we just got back from our own spring break cruise in the Caribbean sea on Royal Caribbean’s Oasis of the Seas, their newest and currently largest cruise ship. I noticed several precautions since the last time we took a cruise several years ago. (BTW:The cruise was fabulous. I highly recommend it!)

From an infectious disease perspective I not only have to congratulate the cruise line on a phenomenal job with the accommodations and entertainment but also the attention to infection control issues.

Most dreaded infection issues are the ones transmitted by either droplet leading to respiratory infections or by contact leading to diarrheal illnesses like norovirus outbreaks that often get media attention that the cruise lines dread.

With regard to respiratory infections the few obvious changes in newer ships is the larger airspaces in common areas. The dining halls, the theaters and the promenade all had higher ceilings than on older cruise ships allowing for greater air exchanges. There was information posted daily about respiratory infections, H1N1 precautions etc.

Diarrheal outbreaks can quickly turn a vacation cruise into a nightmare adventure at sea, especially with the greater number of older persons on cruise ships who may be very susceptible to become very ill. If an effort to control this the cruise ships installed waterless hand sanitizer at the entry points to the ship and to the dining halls. They had staff reminding guests to use them. I was pleasantly surprised to see (non scientific observation) that the compliance rate among passengers was very high. I did not see the opposition from anyone that usually accompanies this kind of added inconvenience. Children, adults all seemed to participate and understand why this is needed. Of course the usual buffet controls were also in place such as sneeze guards, single use of plates and flatware etc.

It is very easy for corporations to go overboard (pun intended) with precautions in a knee jerk effort to control outbreaks at sea. These kind of measures prove to be counter productive in the long run. They create more inconvenience, greater cost, greater customer dissatisfaction without much hard science that they are getting anything for it. I did not see any of these problems on this particular cruise. Whoever is advising them is doing a good job.

All these precautions go a long way in making a successful vacation.
Hats off to Royal Caribbean cruise lines for the effort. We do appreciate it.

Varicella Zoster vaccination

The topic of varicella zoster vaccination has come up several times this week. Probably time for a summary.

Varicella zoster, commonly called shingles is caused by the reactivation (reawakening) of chickenpox virus also called varicella zoster virus (VZV) in the distribution of a nerve root that results in a localized single-sided rash that later blisters (vesicles). The rash itself is not the problem, the pain that occurs due to nerve damage called post herpetic neuralgia can be. Post herpetic neuralgia can be very difficult to manage. This can therefore be very debilitating in the sufferer. The idea of vaccination with the shingles vaccine is to prevent or at least minimize the pain and suffering that goes along with shingles.

One does not acquire shingles from another patient with shingles. As mentioned above. Shingles is the reawakening of the chickenpox that occurred many years ago. In other words the bugs causing shingles are your own. One cannot get shingles from shingles either. But one can get chickenpox from a case of shingles.

Prior to the introduction of chickenpox vaccination, 95.5% of people 20-29 yrs of age and more than 99.6% of people 40 years of age or greater have evidence of previous chickenpox (VZV) infection. All of these persons are at risk of later developing shingles. Once one has recovered from chickenpox the virus does not leave the body. It can remain contained in parts of the nervous tissue called doral nerve root ganglia. As long as our immune system is healthy, the virus remains dormant and contained. However, if our immune system is no longer capable of watching over these prisoners, they can reawaken and lead to shingles. And through that considerable pain and suffering. Shingles develops in about 30% of people over their lifetime. The likelihood of shingles rises with every decade of life over 50. By the time we are in our 80s one in two persons may suffer from shingles. This correlates with the gradual decline in antibodies to varicella. Therefore adequate boosting of anti-varicella antibodies should help reduce the incidence of varicella reactivation.

The varicella vaccine for chickenpox is very effective in preventing primary or initial infection with varicella in children and has become part of the standard vaccination schedule. It is a live attenuated (weakened) vaccine. However when this same vaccine was used in older adults it was found to not stimulate the immune response enough to prevent shingles. Hence the zoster preparation of the vaccine though containing the same weakened live varicella virus is in 14x greater quantity that was found necessary to bring antibody response to protective levels.

Trials from zoster vaccination appear to result in a 51% reduction in the incidence of zoster with a 67% reduction in the incidence of post-herpetic neuralgia (the pain). Those that did have pain despite being vaccinated wen compared to non vaccinated did so for 21 days on average compared to 24 days respectively. The severity of pain was also less in the vaccinated group.

The vaccine is currently indicated in adults aged 60 or over and are not receiving any immunosuppressive therapy such as steroids, chemotherapy. This is a currently recommended as a one time vaccination. This is not to be used to treat active shingles or the pain from recent shingles. Some experts do recommend vaccinating persons with zoster vaccine 12 months after recovering from an episode of zoster.

Most common side effects include pain at the site of injection and occasionally vesicles can develop. No cases of transmission of live virus to other individuals has been seen.

CDC and SHEA disagree on use of masks by healthcare workers

Centers for disease control and prevention (CDC) updated their H1N1 infection control measures for healthcare workers. This does differ though just slightly from the position of The Society for Healthcare Epidemiology of America (SHEA) in that CDC does recommend continuing use of N95 particulate masks when caring for patients with H1N1. Whereas SHEA supports the more traditional use of surgical masks as has been for seasonal influenza.

A study from Ontario, Canada published in the Oct 1, 2009 edition of Journal of American Medical Association (JAMA) did show equivalence of N95 with surgical masks. link

This does put hospitals in a bit of a difficult position. I do agree that considering the volume of patients with suspected H1N1 that are coming into the hospitals that it would not be practical to use our N95 for all patients, we would simply run out.
CDC position
SHEA postion

Why do we need to be vaccinated against influenza every year when other diseases do not?- updated 10/23/09

There are two basic kinds of viruses, those that are made of DNA, the stuff we are made of and RNA viruses. These are viruses that contain a more primitive form of genes.

DNA tends to more stable and reliable from generation to generation. Hepatitis B and Small Pox are examples of DNA viruses.

Influenza on the other hand is an RNA virus and a very unstable RNA virus when compared to other RNA viruses. When it invades a host cell it creates million of copies of itself. In the process it kills the host cell. But because RNA virus have poor error checking due to the lack of a proofreading enzyme called DNA polymerase the copies of itself are very sloppy. Over 80% of these copies are unusable and are not infectious. The remaining ones are infectious to other cells but are still not exact copies of the mother virus. They are therefore “quasi-species” that is; they are very similar but not exact. Over time the virus gradually changes in its genetic makeup.

Our immune system recognizes an invader as alien by its genetics. The specific site on the virus that our antibodies recognize is called the “epitope”. If the genetics of the virus change too much i.e. change the epitope then our immune system takes longer to get into action, sometimes too late. If our immune system has been primed to recognize the viruses epitope from recent experience like a vaccination which is exposing that epitope to our antibody factory. This is akin to getting the floor plans. Then our immune system will shift into high gear much quicker because of the headstart. Hence the need for revaccination every year with a virus that is as close to the current strain as possible.

Plus the antibodies that we do make do not stay around in ample supply forever. In the case on Influenza the antibodies last about 4-5 months. This is also why the sickest people should not get vaccinated too soon before the season. After october 1st is generally a good time to get vaccinated that way we can face the influenza season with the optimal quality and quantity of antibodies.