The WHO site provides information about its mission, objections, functions, key policy, administration, organization, info of various infectious diseases, news and plenty of statistical data which will interested us.
One way to obtain statistical info is WHOSIS (standing for WHO information system) in the INFORMATION SOURCES, especially the Statistical Information in WHOSIS. The purpose of this Statistical Information site is to describe - and to the extent possible provide access to - epidemiological and statistical information available from a variety of sources. Most WHO technical programs make statistical information available, and they may also be linked here. (You also have the possibility to search by keywords through the entire WHO site). It includes mainly Basic Health Indicators, Burden of Disease, Health Personnel, International Classifications, HIV/AIDS, UN Population data, Links to National Health-Related Web sites, Member States of WHO, Links to other Sources of Health Information, etc. Click each of them we can download data in the form of tables.
Another handy button is SEARCH. Click it and enter "statistics" in the blank, then click SEARCH button, we got 61 web pages (maybe more if updated) by click the number (from 1 to 61) at the top of the search page. So I think it is easier to find the data your need by entering the keyword.
In general, we can get so many statistical data about health, diseases, etc at the WHO web sites. Using these data we can do statistical analysis such as regression, predicting the trend, and so on.