With measles cases prominent in the news of late, there have been a few interesting reports and interviews from Queensland's local Acting Senior Director for Communicable Diseases, Dr Stephen Lambert.
Measles virus, has a basic reproduction number (R0) - the average number of new cases from each contact - of 12-18. This defines measles as one of the most contagious infectious diseases of humans. and reflect the ease wish which i is spread through a respiratory route.
Measles also has some serious clinical consequences. Dr Lambert noted that up to a third of infected young adults end up hospitalized. Serious complications can occur including blindness, encephalitis, diarrhoea, ear infection and pneumonia. Most people recover within 2-3 weeks though.
Measles virus is shed from an infected person from 4-days before to 4-days after the characteristic rash appears. Spread occurs from sneezes and coughs that produce small droplets that get inhaled or land on a surface and then are transported by fingers to the nose or mouth. The virus can last out in the open for at least 2-hours.
Measles is a preventable disease. Dr Lambert noted the importance of being up-to-date with your measles vaccination. He has recently had published the idea that airlines could play a greater role in rapidly contacting passengers who may have been in contact with a subsequently identified measles case. They could do this through contact details they already hold, and through social media. This would certainly speed contact tracing and the notification of risk.
Dr Lambert is also busy with E.coli and norovirus outbreaks around south-east Queensland. Still, he has made time to ensure infection prevention and control communication is very well targeted to different audiences - including the public - where it can have a real significant impact. Public health communication, and education, of this quality should be applauded.
He penned a very nice article "Community Immunity", on vaccination for a magazine called Brisbane's Child. In it he notes the importance of vaccinating children to prevent diseases for which there is now little community memory. Diphtheria, tetanus, measles, haemophilus influenza type b, meningococcal C and poliomyelitis are diseases that once caused significant illness, disfigurement and death.
It's testament to the success of vaccines that we see so little of these diseases and their severe impact today. The more recently rolled out rotavirus vaccine has decreased hospitalizations of children due to that viral infection by 90% in Queensland alone. Gastroenteritis hospitalizations are down by 60% overall (highlighting the impact of rotavirus).
There is a fantastic quote in this article that touches on the wider impact on not vaccinating your children. Basically, if your child had a peanut allergy you wouldn't expose them to peanuts, or be very happy if someone else did.
Why then make the choice to allow your children to become seriously ill by acquiring a preventable disease if there is a safe and simple way to avoid that? Also, there are some people who cannot be vaccinated and there are some people in whom the vaccine does not "take".
Herd immunity protects them because the virus cannot spread as effectively when it's got too few unprotected people to infect and pass among. If the herd does not have a good uptake of vaccination though then it cannot protect them. It's also worth noting that vaccines do not offer absolute immunity to infection. The vaccine does create a shield that prevents you from breathing the virus in and having it land on your cells but they do stop the severe disease associated with infection.