How do I make the correct fadein to dynamically update content using jquery?

I have a .txt file that I need to include in a page that dynamically refreshes every 5 seconds, so I need to refresh it with ajax so that the updated content can be seen without refreshing the page. I want to make it disappear into the div, every 5 seconds of refresh.

I am currently doing it in a way that looks pretty ugly

function getSearches() {
      $("#latest_searches").animate({ 
        opacity: 0.3
      }, 1000 );

$("#latest_searches").load("_latest_searches.php", '', callback);
}

function callback() {
  $("#latest_searches").animate({ 
        opacity: 1
      }, 1000 );

setTimeout("getSearches();", 5000);
}

$(document).ready(getSearches);